Previous Page 290

Purification of Organic Chemicals

Norcamphor (bicyclo[2.2.l]heptan-2-one) Norcholanic acid acid.

[497-38-11 M 110.2, m 94-95O. Crystd from water.

[511-18-21 M 346.5, m 177O, 186O, [a]i0+32O (EtOH). Crystd from acetic

Norcodeine [467-15-21 M 285.3, m 185O, 186O. Crystd from acetone or ethyl acetate. Nordihydroguaiaretic acid [500-38-91 M 302.4, m 184-185O. Crystd from dilute acetic acid. Norleucine [R: 327-56-01 [S: 327-57-11 M 117.2, m 301O [o]:!~ f28O (c 5, 5M HCl); [RS: 06-81 m 297-300°. Crystd from water. Norvaline [R: 2031-12-91 [S: 6600-40-41 M 117.2, m 305O(dec), [a]:!6 Crystd from aqueous EtOH or water.

616-

f25O (c 10, 5M HCl).

(acid Novobiocin [303-81-11 M 612.6, two forms m 152-156O and m 174-178O, h,,,.330nm EtOH), 305nm (alk EtOH), [0r];~-47O (c 1, EtOH). Crystd from EtOH and stored in the dark. The sodium salt can be crystd from MeOH, then dried at 60°/0.5mm. [Sensi, Gallo and Chiesa AC 29 1611 1953. Nuclear Fast Red [6409-77-41 M 357.3, m >290°(dec). h,,, 518nm. A soln of 5g of the dye in 25Oml of warm 50% EtOH was cooled to 15O for 36h, then filtered on a Biichner funnel, washed with EtOH until the washings were colourless, then with lOOml of ethyl ether and dried over P2O5. [Kingsley and Robnett AC 33 552 19611. Nylon powder. Pellets were dissolved in ethylene glycol under reflux. Then ppted as a white powder on addition of EtOH at room temperature. This was washed with EtOH and dried at 100° under vacuum.

n-octacosane

[630-02-41 M 394.8, m 62.5O. Purified by forming its adduct with urea, washing and crystallising from acetone/water. [McCubbin TFS 58 2307 19621. Crystd from hot, filtered isopropyl ether s o h (IOml/g).

n-Octadecane [593-45-31 M 254.5, m 28.1°, b 173.5°/10mm, 316.1°/760mm, d i O 0.7768, n 1.4390. Crystd from acetone and distd under reduced pressure from sodium. n-Octadecanoic acid [124-07-21 M 144.2, m 16.7-17O, b 144-1450/27mm, d i O 0.911, n 1.428. Fractionally crystd by partial freezing. Dried with Linde type 4A molecular sieves and fractionally distd under reduced pressure. 1-Octadecanol

see n-octadecyl alcohol.

Octadecyl acetate [822-23-11 M 312.5, m 32.6". Distd under vac, then crystd from ethyl ether/MeOH. n-Octadecyl alcohol [112-92-51 M 270.5, m 61°, b 153-1540/0.3mm. Crystd from MeOH, or dry ethyl ether and benzene, then fractionally distd under reduced pressure. Purified by column chromatography. Freed from cetyl alcohol by zone melting. Octadecyl ether [6297-03-61 M 523.0, m 59.4O. Vacuum distd, then crystd from MeOH/benzene. Octadecyltrimethylammonium bromide

vacuum desiccator.

[1120-02-1] M 392.5. Recrystd from EtOH. Dried in a

29 1

Purification of Organic Chemicals

2,3,7,8,12,13,17,18-Octaethylporphin

[2683-82-11 M 534.8. Chromatographed on S i 0 2 using

CHCl3 as eluent.

Octafluoropropane (profluorane) [76-19-71 M 188.0, b -38". Purified for pyrolysis studies by passage through a copper vessel containing CoF3 at about 270°, then fractionally distd. [Steunenberg and Cady JACS 74 4165 19521. [1079-71-61 M 186.3, m 78". Crystd from EtOH, then zone

1,2,3,4,6,7,8,9-0ctahydroanthracene refined.

Octamethylcyclotetrasiloxane 1.396. Purified by zone melting.

[556-67-21

M 296.6, m 17.3", b 175-176O, d i 0 0.957, n

Octan-l,S-diol

[629-41-41 M 146.2, m 59-61", b 172°/0.2mm. Recrystd from EtOH.

Octan-4,5-diol

see dipropylene glycol.

n-Octane [111-65-9] M 114.2, b 126.5", d i 0 0.704, n 1.39743, n25 1.39505. E x t r a c t e d repeatedly with conc H2S04or chlorosulphonic acid, then washed with water, dried and distd. Also purified by azeotropic distn with EtOH, followed by washing with water to remove the EtOH, drying and distilling. For further details, see n-heptane. Also purified by zone melting. 1-Octanethiol [ I 1 1-88-61 M 146.3, b 86°/15mm, 197-200°/760mm, d i 0 0.8433, Passed through a column of alumina [Battacharyya et al. JCSFTI 82 135 19861.

n 1.4540.

Octaphenylcyclotetrasiloxane [546-56-51 M 793.2, m 201-202", b 330-34°/760mm. from benzene/EtOH or glacial acetic acid.

Crystd

1-Octene [ I l l - 6 6 - 0 1 M 112.2, b 121°/742mm, dO : 0.716, n 1.4087, (trans)-2-Octene [13389-42-91 M 112.2, b 124-124.5°/760mm, di0 0.722, n 1.4132. D i s t d under nitrogen from sodium. [Removes water and peroxides]. Peroxides can also be removed by percolation through dried, acid washed alumina. Stored under nitrogen in the dark. [Strukul and Michelin JACS 107 7563 19851.

n-Octyl alcohol [ I l l - 8 7 - 5 1 M 130.2, b 9S0/19rnm, 195.3"/760mm, d 0.828, n 1.43018. Fractionally distd under reduced pressure. Dried with sodium and again fractionally distd or refluxed with boric anhydride and distd (b 195-205O/5mrn), the distillate being neutralised with NaOH and again fractionally distd. Also purified by distn from Raney nickel and by preparative GLC. n-Octylammonium 9-anthanilate from ethyl acetate.

[88020-99-91 M 351.5, m 134-135". Recrystd several times

n-Octylammonium hexadecanoate [88020-97-71 M 385.7, m 52-53". Purified by several recrystns from n-hexane or ethyl acetate. The solid was then washed with cold anhydrous ethyl ether, and dried in vacuo over P205. n-Octylammonium octadecanoate hexadecanoate above. n-Octylammonium hexadecanoate above.

tetradecanoate

1 3 2 5 8 0 - 9 2 - 0 1 M 413.7, m 56-57". Purified as for the

[ 5 4 4 - 6 1 - 8 1 M 358.6, m 46-48". Purified as for the

4-Octylbenzoic acid [3575-31-31 M 234.3, m 99-100°. Crystd from EtOH has m 139O; crystd from aq EtOH has m 9 9 - 1 0 0 O .

292

Purification of Organic Chemicals

n-Octyl bromide [111-83-1] M 193.1, b 201.5", d i 0 1.118, nZ51.4503. washed with water, dried with K2C03 and fractionally distd.

Shaken with H 2 S 0 4 ,

4-(tert-Octyl)phenol [140-66-91 M 206.3, m 85-86". Crystd from n-hexane. 1-Octyne [629-05-01 M 110.2, b 126.2"/760mm, d i O 0.717, n25 1.4159. Distd from NaBH4 to remove peroxides. P-Oestradiol [50-28-21 M272.4, m 179O, [a];' +SO" (c 1, dioxane), P-Oestradiol-3-benzoate [SO-50-01 M 376.5, m 194-19S0, +700 (c 2, dioxane), C r y s t d from EtOH

[01]iq0~

Oleic acid [112-80-1] M 282.5, m 16", b 3600(dec), d i O 0.891, n30 1.4571. Purified by fractional crystn from its melt, followed by molecular distn at 10-3mm,or by conversion to its methyl ester, the free acid can be crystd from acetone at - 4 O O to - 4 5 O (12mlIg). For purification by the use of lead and lithium salts, see Keffler and McLean [JCS Ind (London)54 176T 19351. Purification based on direct crystn from acetone is described by Brown and Shinowara [JACS59 6 1937. Oleyl alcohol [142-28-21 M 268.5, b 182-184°/1.5mm, d$O 0.847, nZ7e51.4582. fractional crystn at -400 from acetone, then distd under vacuum. Opianic acid (2-formyl-4,5-dimethylbenzoicacid) water.

Purified by

[519-05-I] M 210.2, m 150". Crystd from

Orcinol [504-15-41 M 124.2, m 107S0, (H20) m 59-61". Crystd from CHC13/benzene (2:3). L-Ornithine [70-26-81 M 132.2, m 140°, [a];5+16O (c 0.5, HzO). Crystd from water containing ImM EDTA (to remove metal ions). L-Ornithine monohydrochloride [3184-13-21 M 168.6, [ o I ] ~ +28.3O (5M HCI). L i k e 1 y impurities are citrulline, arginine and D-ornithine. Crystd from water by adding 4 volumes of EtOH. Orotic acid (H20) [50887-69-91 M 174.1, m 235-346"(dec). Crystd from water. Orthanilic acid (2-aminobenzenesulphonic acid) [88-21-11 M 173.2, m >300"(dec). Crystd from aqueous soln, containing 2Oml of conc HCl per L, then crystd from distilled water. Ouabain [630-60-41 M 728.8, m 18O0(dec), [~r]::~ 130°. Stored in the dark.

-30" (c 1, HzO). Crystd from water.

Dried at

Oxalic acid (2H20) [630-60-41 M 90.0, m 101.5"; [anhydrous 144-62 -71 m 189.5". Crystd from distilled water. Dried in vacuum over HzS04. The anhydrous acid can be obtained by drying at 1000 overnight. Oxaloacetic acid [328-42-71 M 132.1, m 160°(decarboxylates). Crystd from boiling ethyl acetate, or from hot acetone by addition of hot benzene. 2-Oxaloglutaric acid [328-50-71 M 146.1, m 114". Crystd repeatedly from acetonebenzene. Oxamide [471-46-51 M 88.1, m >320°(dec). Crystd from water, ground and dried in an oven at 1500. Oxamycin

see R-4-amino-3-isoxazolidone.

2-Oxazolidinone

[497-25-61 M 87.1, m 89-90", 91O. Crystd from benzene.

2-Oxohexamethyleneimine

see E-caprolactam.

293

Purification of Organic Chemicals

Oxalylindigo [2533-00-81 M 316.3. Recrystd twice from nitrobenzene and dried by heating in vucuo for several hours. [Sehanze et al. JACS 108 2646 19861. Oxetane (1.3-trimethylene oxide) [503-30-01 M 58.1, b 45-46°/736mm, 47-49O/atm, 48°/760mm, d:' 0.892, ni'1.395. Distd from sodium metal. Also purified by preparative gas chromatography using a 2m silica gel column. Alternatively add KOH pellets (50g for l00g of oxetane) and distil through a column packed with 1/4in Berl Saddles and the main portion boiling at 45-50° is collected and redistd over fused KOH. [Noller Org Synth Coll Vol I11 835 1955; Dittmer et al. JACS 79 4431 19571. Oxine Blue [3733-85-51 M 369.4, m 134-135O. Recrystd from EtOH. Dried over H2S04. 2,2'-Oxydiethanol see diethylene glycol.

Palmitic acid

(hexadecanoic acid) [57-10-31 M 256.4, m 63-64O. Crystd from EtOH. Purified via the methyl ester (b 193-194O/12mm,dg1.4359) as for capric acid, or by zone melting.

R-Pantothenic acid EtOH.

[867-81-21 M 241.2, m 122-124O, [or]2,5+27O (c 5, H2O). Crystd

from

Papain see Chapter 5. [2.2]-Paracyclophane (tricyclo[8.2.2.24~7]hexadeca-4,6,lO,l2,l3,l5-hexaene) [1633-22-31 M 208.3, m 284O, 285-287O, 286-288O, 288-290°. Purified by recrystn from AcOH. 'H-NMR 6: 1.62 (Ar-H) and -1.71 (CH2) ppm [Waugh and Fessenden JACS 79 846 1957; IR and UV: Cram et al. JACS 76 6132 1954, Cram and Steinberg JACS 73 5691 1951; complex with unsaturated compounds: Cram and Bauer JACS 81 5971 1959; Syntheses: Brink S 807 1975, Givens et al. JOC 44 16087 1979, Kaplan et al. TET LETT 3665 19761. Paraffin (oil) [8012-95-11 d 0.880, n 1.482. Treated with fuming H2S04, then washed with water and dilute aqueous NaOH, then percolated through activated silica gel. Paraffin Wax. Melted i n the presence of NaOH, washed with water until all of the base had been removed. The paraffin was allowed to solidify after each wash. Finally, 5g of paraffin was melted by heating on a waterbath, then shaken for 20-30min with lOOml of boiling water and fractionally crystd.

-

(4,4 4 t r i a m i n o t r i t y 11 i u m [trip h e n y 1methane ] carbon i u m ion, Parafuchsin pararosaniline, paramagenta) [467-62-91 M 305.4. Dissolve in EtOH (1.16g in 30ml), filter and add aqueous NH3 till neutral and ppte by adding H 2 0 giving 0.8g m 247O dec (sintering At 230O). Dissolve in EtOH neutralise with NH3 add 0. l g of charcoal filter, and repeat, then add H20 (100ml) to ppte the colourless carbinol dry, m 257O dec (sintering at 232O). [Weissberger and Theile JCS 148 19341. The carbinol (pseudobase) was said to have m 232O (1 86O dec), and is slightly sol in H20 but sol in acids and EtOH, and has a pKa of 7.57 whereas the free base has pKa > 13 [Goldacre and Phillips JCS 172 19491. The perchlorate (dark red with a green reflex) has m 30O0 and explodes at 3 17O [Dilthey and Diaklage J Prukt Chem [2] 129 19311. I,

Paraldehyde [30525-89-41 fractionally distd.

M 132.2, m 12S0, 124O, d 0.995, n 1.407. Washed with water and

Patulin [149-29-11 M 154.1, m l l O o . Crystd from ethyl ether or chloroform. (Highly TOXIC). Pavatrine hydrochloride over P2O5 under vacuum.

[548-65-21 M 333.7, m 143-144O. Recrystd from isopropanol, and dried

294

Purification of Organic Chemicals

Pectic acid, Pectin see Chapter 5. Pelargonic acid (nonanoic acid) [112-05-01 M 158, m 15O, b 98.9°/lmm, 225O/760mm. Esterified with ethylene glycol and distd. (This removes dibasic acids as undistillable residues.) The acid was regenerated by hydrolysing the ester. Penicillic acid (90-65-31 M 158.2, m 58-64O (H20), 83-84O (anhydrous). Crystd from water as the monohydrate, or from pet ether. Pentaacetyl-a-D-glucopyranose [604-68-21 M 390.4, m 112O, [aI2O6+1 19O (c 5, CHC13), 9 Pentaacetyl-P-D-glucopyranose [604-69-31 M 390.4, m 131°, [a]2 546 +5O(c 5, CHC13). Crystd from EtOH. Pentabromoacetone

[79-49-21 M 452.6, m 76O. Crystd from ethyl ether or EtOH.

Pentabromophenol [608-71-91 M 488.7, m 229O. Purified by crystn (charcoal) from toluene then from CC14. Dried for 2 weeks at ca 75O. 1-Pentacene [13360-61-71 M 278.4, m 3 0 0 O . Crystd from benzene. Pentachloroethane (pentalin) [76-01-71 M 202.3, b 69O/37mm, 152.2O/64mm, 162.0°, d 1.678, n15 1.50542. Usual impurities include trichloroethylene. Partially decomposes if distd at atmospheric pressure. Drying with CaO, KOH or sodium is unsatisfactory because HCl is split off. It can be purified by steam distn, or by washing with conc H2SO4, water, and then aqueous K2CO3, drying with solid K2CO3 or CaS04, and fractionally distd under reduced pressure. Pentachloronitrobenzene Pentachlorophenol vacuo.

[82-68-81 M 295.3, m 146O. Crystd from EtOH.

[87-86-51 M 266.3, m 190-191O. Twice crystd from tolueneEtOH.

Sublimed in

Pentachloropyridine [2176.62-71 M 251.3, m 122-124O, 123O, 124O, 124-125O, 125-126O, b 279-28O0/atm. Purified by recryst from EtOH or aqueous EtOH. It sublimes at 150°/3mm. [den Hertog et al. Rec Trav Chim Pays Bas 69 673 1950; Schikh et al. B 69 2604 19361. Pentachlorothiophenol

[133-49-31 M 282.4, m between 228O and 235O. Crystd from benzene.

Pentachrome Azure Blue B. Crystd from MeOH. Pentadecafluoro octanoic acid (perfluorocaprylic acid) [335-67-11 M 414.1, m 54.9-55.6O, b 189°/736mm. Recrystd from CCl4 and toluene, and can be distd. It forms micelles in H2O and the solubility is 1% in H20. [Bernett and Zisman J P C 63 191 1 1959; IR: Bro and Sperati J Polymer Sci 38 289 19591. Pentadecanoic acid [1002-84-21 M 242.4, m 51-53O, b 158°/lmm, 257O/760mm, dg0 0.8424. Purification as for hexadecanoic acid. Pentadecanolide (l-oxacyclohexadecan-2-one,pentadecanoic-a-lactone, 15-hydroxypentadecanoic lactone, exaltolide, Tibetolide) [106-02-51M 240.4, m 34-36O, 37-37S0, 37-38O, b 102- 103°/0.03mm, 112-114°/0.2mm, 137O/2mm, 169O/10-1lmm, d:' 0.9401. It has been recrystd from MeOH (4parts) at - 1 5 O . [Hundiecker and Erlbach B 80 135 1947; Galli and Mandolini Org Synth 58 100 1978; Demole and Enggist H C A 11 2318 19781. Penta-1,3-diene

[cis: 1574-41-01, [trans: 2004-70-81 M 68.1, b 42O, d 0.680, n 1.4316,

Purification of Organic Chemicals

Penta-1,4-diene [591-93-51 M 68.1, b 25.8-26.2°/756mm, d 0.645, n 1.3890. NaBH4. Purified by preparative gas chromatography. [Reimann et al. JACS 108 5527 19861. Penta-2,4-dione

295

Distd from

see acetylacetone.

Pentaerythritol [115-77-51 M 136.2, m 260.5O. Refluxed with an equal volume of MeOH, then cooled and the ppte dried at 90°. Crystd from dil aq HCl. Sublimed under vacuum at 2000. Pentaerythritol tetraacetate [597-71-71 M 304.3, m 78-79O. Crystd from hot water, then leached with cold water until the odour of acetic acid was no longer detectable. Pentaerythrityl laurate [13057-50-61 M 864.6, m SOo. Crystd from pet ether. Pentaerythrityl tetranitrate. [78-11-5] M 316.2, m 140.1O. Crystd from acetone or acetoneEtOH. EXPLOSIVE. Pentaethylenehexamine [4067-16-71 M 232.4. Fractionally distd twice at 10-20mm, the fraction boiling at 220-250° being collected. Its soln in MeOH (40ml in 250ml) was cooled in an ice-bath and conc HCl was added dropwise with stirring. About 50ml was added, and the ppted hydrochloride was filtered off, washed with acetone and ethyl ether, then dried in a vacuum desiccator. [Jonassen et al. JACS 79 4279 19-57. Pentafluorobenzene {363-72-41 M 168.1, b 8S0/atm, 85-86°/atm, 88-89°/atm, di0 1.524, n i o 1.3931. Purified by distn and by gas chromatography. IR film: 1535 and 1512 cm-l (benzene ring). [UV: Stephen and Tatlow Chemistry and Industry (London) 821 1957 ; Nield et al. JCS 166 19591.

2,3,4,5,6-Pentafluorobenzoic acid [ 6 0 2 - 9 4 - 8 1 M 212.1, m 101-103°, 103-104O, 104-105O, 106-107O. Dissolve in Et20, treat with charcoal, filter, dry (CaS04), filter, evaporate and recrystallise residue from pet ether (b 90-100O) after adding a little toluene to give large colourless plates. W (H20): hmax 265nm (E 761). The S-benzylisothiuronium salt has m 187O after recrystn from H20. [McBee and Rapkin JACS 73 1366 1951; Nield et al. JCS 166, 170 19591. 0-(2,3,4,5,6-Pentafluorobenzyl)hydroxylamine hydrochloride (PFBOA) [57981-02-91 M 249.6, m 215,215-216. Recrystd from EtOH to form colourless leaflets. Drying the compound at high vacuum and elevated temperature will result in losses by sublimation. [Youngdale J Pharm Sci 65 625 1976; Wehner and Handke J Chromatography 177 237 1979; Nambara et al. give incorrect m as 115-1 16O J Chromatography 114 8 1 19751.

2,3,4,5,6-Pentafluorophenol [ 7 7 1 - 6 1 - 9 1 M 184.1, m 33-3S0, 38.5-39S0, b 72-74°/48mm, 142- 144O/atm, 143O/atm, ny1.4270 (liquid prep). A hygroscopic low melting solid not freely soluble in H20. Purified by distn, preferably in a vacuum. It has pKa17 of 5.53 in H20 [Forbes et al. JCS 2019 1959; IR and pKa: Birchall and Haszeldine JCS 13 19591. IR film: 3600 (OH) and 1575 (fluoroaromatic breathing) cm-*. The benzoyl derivative has m 74-75O, 3,4-dinitrobenzoyl derivative has m 107O, the fosylate has m 64-65O (from EtOH) and the K salt crystallises from MezCO, m 242O dec, with 1H20 salt the m is 248O dec and the 2H20 salt has m 245O dec. R - ( + ) - [104371-21-31 S - ( - ) - [ 1 0 4 3 7 1 - 2 0 - 2 1 1-(Pentafluoropheny1)ethanol M 212.1, m 4142O,42O, 42.5-43O, [~x]2540~+9O, [ a ] y + 7 S o (c 1, n-pentane). Recrystd from n-pentane at -40° and vacuum sublimed at room temp at 0.3mm (use ice cooled cold finger). It has also been purified by column chromatography through Kieselgel 60 (0.063-0.2mm mesh, Merck), eluted with EtOAc-n-hexane (1 :5), then recrystd from n-pentane and vacuum sublimed. It has RF on Kieselgel 60 F254 TLC foil and eluting with EtOAc-n-hexane (15). [Meese A 2004 19861. The racemate [75853-08-61 has m 32-34O, b 77-79O/8mm, 8082O/37mrn, 1.4426 and the 3,4-dinitrobenzoate has m 83O [Nield et al. JCS 166 19591.

4'

296

Purification of Organic Chemicals

2,2,3,3,3-Pentafluoropropan-l-ol [422-05-91 M 150.1, b 80°, d 1.507, n 1.288. Shaken with alumina for 24h, dried with anhydrous K2CO3, and distd, collecting the middle fraction (b 80-81O) and redistilling. Pentafluoropyridine [700-16-31 M 169.1, m -41S0, b 83S0, 83.S0, 83-85O, d$' 1.609, nko 1.3818. Distd through a concentric tube column; has h max in cyclohexane at 256.8nm. [Chambers et al. JCS 3573 19641; 19F NMR: Bell et al. J Fluorine Chem 1 51 19711. The hexajluoroantimonate has m 98102O dec.

2',3,4',5,7-Pentahydroxyflavone

see Morin.

Pentamethylbenzene [700-12-91 M 148.3, m 53.5-55.1O. Successively crystd from absolute EtOH, toluene and MeOH, and dried under vacuum. [Rader and Smith JACS 84 1443 19621. It has also been crystd from benzene or aqueous EtOH, and sublimed.

1,5-Pentamethylenetetrazole ether.

[54-95-51 M 138.2, m 60-61°, b 194O/12mm.

Crystd from ethyl

n-Pentane [log-66-01 M 72.2, b 36.1°, d 0.626, n 1.35748, n25 1.35472. Stirred with successive portions of conc H2SO4 until there was no further coloration during 12h, then with 0.5N KMnO4 in 3M H2SO4 for 12h, washed with water and aqueous NaHC03. Dried with MgS04 or Na2S04, then P2O5 and fractionally distd through a column packed with glass helices. It was also purified by passage through a column of silica gel, followed by distn and storage with sodium hydride. An alternative purification is by azeotropic distn with MeOH, which is subsequently washed out from the distillate (using water), followed by drying and distn. For removal of carbonyl-containing impurities, see n-heptane. Also purified by fractional freezing (ca 40%) on a copper coil through which cold air was passed, then washed with conc H2SO4 and fractionally distd. 2P-Pentanedione

see acetylacetone.

Pentane-1-thiol [ I 10-66-71 M 104.2, b 122.9O/697.5mrn, d25 0.8375. Dissolved in aqueous 20% NaOH, then extracted with a small amount of ethyl ether. The s o h was acidified slightly with 15% H2SO4. and the thiol was distd out, dried with CaS04 or CaC12, and fractionally distd under nitrogen. [Ellis and Reid JACS 54 1674 19321. Pentan-1-01 see n-amyl alcohol. Pentan-2-01 [6032-29-71 M 88.2, b 119.9O, d 0.810, n 1.41787, n25 1.4052. Pentan-3-01 [684-02-11 M 88.2, b 116.2O, d 0.819, n25 1.4072. Refluxed with CaO, distd, refluxed with magnesium and again fractionally distd. Pentan-3-one [96-22-01 M 86.1, b 101.7O, d 0.813, n 1.3924, n25 1.3900. for 2h, then left overnight with fresh CaC12, filtered and distd. Pentaquine monophosphate

Refluxed with CaC12

[5428-64-81 M 395.6, m 189-190O. Crystd from 95% EtOH.

Pent-2-ene (mixed isomers) [109-68-21 M 70.1, b 36.4O, d 0.650, n 1.38003, n25 1.3839. Refluxed with sodium wire, then fractionally distd twice through a Fenske column. cis-Pent-2-ene [627-20-31 M 70.1, b 37.1°, d 0.657, n 1.3830, n25 1.3798. Dried with sodium wire and fractionally distd, or purified by azeotropic distn with MeOH, followed by washing out the MeOH with water, drying and distilling. Also purified by chromatography through silica gel and alumina [Klassen and Ross JPC 91 3668 19871.

Purification of Organic Chemicals

297

trans-Pent-2-ene 1646-04-81 M 70.1, b 36S0, d 0.6482, n 1.3793. It was treated as above and washed with water, dried over anhydrous Na2C03, and fractionally distd. The middle cut was purified by two passes of fractional melting. Pentobarbital (5-ethyl-5-l'-methylbutylbarbituric acid, Nembutal) 176-74-41 M 226.4, m -127O(dec). Soln of the sodium salt in 10% HCl was prepared and the acid was extracted by addition of ether. Then purified by repeated crystn from CHC13. [Bucket and Sandorfy JPC 88 3274 19841. Pentyl acetate (n -amyl acetate) [628-63- 71 M 130.2, b 147-149O/atm, 149.55O, 149.2O/atm, d:' 0.8753, nko 1.4028. Purified by repeated fractional distn through an efficient column or spinning band column. [Timmermann and Hennant-Roland J Chimie Phys 52 223 1955; Mumford and Phillips JCS 75 1950; 'H NMR: Crawford and Foster Cunud J Physics 34 653 19561. Pentyl- see tert-butyl. tert- Pentyl see tert- a my I. neo-Pentyl alcohol see 2,2-dimethyl-l-propanol. Pent-2-yne [627-21-41 M 68.1, b 26O/2.4mm, d 0.710, nZ51.4005. Stood with, then distd at low pressure from, sodium or N a B h . Pepsin see Chapter 5. Perbenzoic acid [93-59-41 M 138.1, m 41-43O. Crystd from benzene. Readily sublimed. Perchlorobutadiene [87-68-31 M 260.8, b 144.1°/100mm, 210-212°/760mm, d 1.683, n 1.5556. Washed with four or five l/lOth volumes of MeOH (or until the yellow colour has been extracted), then stirred for 2h with H2SO4, washed with distilled water until neutral and filtered through a column of P2O5. Distd under reduced pressure through a packed column. [Rytner and Bauer JACS 82 298 19601. Perfluorobutyric acid 137.5-22-41 M 214.0, m -17S0, b 120°/735mm, d 1.651, d61.295. Fractionally distd twice in an Oldershaw column with an automatic vapour-dividing head, the first distn in the presence of conc H2S04 as a drying agent. Perfluorocyclobutane 1115-25-31 M 200.0, m -40°, b -So,d-20 1.654, do 1.72. Purified by trapto-trap distn, retaining the middle portion. Perfluorocyclohexane 1355-68-01 M 300.1, m 5 l 0 (sublimes), b 52O. Extracted repeatedly with MeOH, then passed through a column of silica gel (previously activated by heating at 250O). Perfluoro-1,3-dimethylcyclohexane 1335-27-31 M 400.1, b l o l o , d 1.829, n 1.300. Fractionally distd, then 35ml was sealed with about 7g KOH pellets in a borosilicate glass ampoule and heated at 135O for 48h. The ampoule was cooled and opened, and the liquid was resealed with fresh KOH in another ampoule and heated as before. This process was continued until no further decomposition was observed. The substance was then washed with distilled water, dried (CaS04) and distd. [Grafstein AC 26 523 19541. Perfluoroheptane 1335-57-91 M 388.1, b 99-101°, d25 1.7200. Purified as for perfluorodimethylhexane. Other procedures include shaking with H2SO4, washing with water, drying with P2O5 for 48h and fractionally distilling. Alternatively, it has been refluxed for 24h with saturated acid KMn04 (to oxidise and remove hydrocarbons), then neutralised, steam distd, dried with P2O5, and passed slowly through a column of dry silica gel. It has been purified by fractional crystn, using partial freezing. Perfluoro-n-hexane [355-42-01 M 338.1, m -4O, b 58-60°, d 1.684. Purified by fractional freezing. The methods described for perfluoroheprune should be applicable here.

Purification of Organic Chemicals

298

Perfluoro(methy1cyclohexane) [355-02-21 M 350.1, b 76.3O, d25 1.7878. Refluxed for 24h with saturated acid KMnO4 (to oxidise and remove hydrocarbons), then neutralised, steam distd, dried with P2O5 and passed slowly through a column of dry silica gel. [Glew and Reeves JPC 60 615 19561. Also purified by percolation through a l m neutral activated alumina column, and 'H-impurities checked by NMR. Perfluorononane [375-96-21 M 488.1. Purified as for perjluorodimethylcyclohexane. Perfluoropropane [76-19-71 M 188.0. Purified by several trap-to-trap distns. Perfluorotripropylamine [338-83-01 M 521.1. Purified as for perjluorodimethylcyclopropane. Pericyazine [2622-26-61 M 365.4. Recrystd from a saturated s o h in cyclohexane. Perylene [198-55-01 M 252.3, m 273-274O. Purified by silica-gel chromatography of its recrystd picrate. [Ware JACS 83 4374 19611. Crystd from benzene, toluene or EtOH and sublimed in a flow of oxygen-free nitrogen. [Gorman et al. JACS 107 4404 1985; Johansson et al. JACS 109 7374 1987. Petroleum ether [8032-32-41 b 35-60°, d 0.640, n 1.363. Shaken several times with conc H2SO4, then 10% H2SO4 and conc KMnO4 (to remove unsatd, including aromatic, hydrocarbons) until the permanganate colour persists. Washed with water, aqueous Na2C03 and again with water. Dried with CaC12 or Na2S04, and distd. It can be dried further using CaH2 or sodium wire. Passage through a column of activated alumina, or treatment with CaH2 or sodium, removes peroxides. For the elimination of carbonyl-containing impurities without using permanganate, see n-heptane. These procedures could be used for all fractions of pet ethers. R(-)-a-Phellandrene (4221-98-11 M 136.2, b 61°/11mm, 1.471. Purified by gas chromatography on an Apiezon column.

175-176°/760mm, d 0.838, n

Phenacetin see p-acetophenetidine. Phenacylamine hydrochloride [Castro JACS 108 4179 19861.

[5468-37-11 M 171.6, m 194O(dec). Recrystd from 2-propanol

Phenacyl bromide see 2-bromoacetophenone. Phenanthrene [85-01-81 M 178.2, m 9 8 O . Likely contaminants include, anthracene, carbazole, fluorene and other polycyclic hydrocarbons. Purified by distn from sodium, boiling with maleic anhydride in xylene, crystn from acetic acid, sublimation and zone melting. Has also been recrystd repeatedly from EtOH, benzene or pet ether (b 60-70°), with subsequent drying under vacuum over P2O5 in an Abderhalden pistol. Feldman, Pantages and Orchin [JACS 73 4341 19511 separated from most of the anthracene impurity by refluxing phenanthrene (671g) with maleic anhydride (194g) in xylene (1.25L) under nitrogen for 22h, then filtered. The filtrate was extracted with aqueous 10% NaOH, the organic phase was separated, and the solvent was evaporated. The residue, after stirring for 2h with 7g of sodium, was vacuum distd, then recrystd twice from 30% benzene in EtOH, then dissolved in hot glacial acetic acid (2,2ml/g), slowly adding an aqueous s o h of CrO3 (60g in 72ml H20 added to 2.2L of acetic acid), followed by slow addition of conc H2SO4 (30ml). The mixture was refluxed for 15min, diluted with an equal volume of water and cooled. The ppte was filtered off, washed with water, dried and distd, then recrystd twice from EtOH. Further purification is possible by chromatography from CHC13 s o h on activated alumina, with benzene as eluent, and by zone refining. Phenanthrene-9-aldehyde sublimed at 95-98O/O.O7rnm.

[4707-71-51 M 206.3, m 102.2-103°/12mm. Crystd from EtOH and

9,lO-Phenanthrenequinone [84-11-71 M 208.2, m 208O. Crystd from dioxane or 95% EtOH and dried under vacuum.

Purification of Organic Chemicals

299

Phenanthridine [229-87-81 M 179.2, m 106.5O. Purified via the HgC12 addition compound formed when phenanthridine (20g) in 1:1 HCI (1OOml) was added to aqueous HgC12 (6Og in 3L), and the mixture was heated to boiling. Conc HCl was then added until all of the solid had dissolved. The compound separated on cooling, and was decomposed with strong aqueous NaOH (ca 5M). Phenanthridine was extracted with ethyl ether and crystd from pet ether (b 80-looo) or ethyl acetate. [Cumper, Ginman and Vogel JCS 45218 19621. Also purified by zone melting. 1,lO-Phenanthroline (o-phenanthroline) [66-71-71 M 198.2, m 88-10lo, 108-llOo (HzO), 118O (anhydrous), b >30O0. Crystd as its picrate ( m 191O) from EtOH, then the free base was liberated, dried at 78O/8mm over P2O5 and crystd from pet ether (b 80-looo). [Cumper, Ginman and Vogel JCS 1188 19621. It can be purified by zone melting. Also crystd from hexane, benzene/pet ether (b 40-60°) or sodiumdried benzene, dried and stored over H2SO4. The monohydrate is obtained by crystn from aqueous EtOH or ethyl acetate. It has been crystd from H20 (300 parts) to give the monohydrate m 102-103O and sublimes at 10-3mm [Fielding and LeFevre JCS 1811 19511. The anhydrous compound has m 118O (after drying at high vacuum at 80°), also after recrystn from pet ether or C6H6 (70 parts) and drying at 78O/8mm. [W:Badger et al. JCS 3199 19511. It has a pKa in H20 of 4.857 (25O) or 5.02 (20O) and 4.27 in 50% aq EtOH (20O) [Albert et al. JCS 224019481. 1,lO-Phenanthroline hydrochloride (o-phenanthroline hydrochloride) [3829-86-51 M 243.7, m 212-219O. It crystallises from 95% EtOH, m 212-219O as the monohydrate, the half hydrate has m 217O. The 3HCZ has m 143-145O (sinters at 128O) [Thevenet et al. Acra Cryst Sect B 33 2526 19771.

4,7-Phenanthroline-5,6-dione [84-12-81 M 210.2, m 295O(dec). Crystd from MeOH. Phenazine [92-82-01 M 180.2, m 171O. Crystd from EtOH, CHC13 or ethyl acetate, after pre-treatment with activated charcoal. It can be sublimed in vacuo, and zone refined. Phenazine monosulphate Crystd from EtOH (charcoal).

[299-11-61 M 306.3, m 155-157O (or 198O dec on rapid heating).

Phenethylamine [64-04-01 M 121.2, b 87°/13mm, d 0.962, n 1.535. Distd from CaH2, under reduced pressure, just before use. Phenethyl bromide [103-63-91 M 185.1, b 92°/11mm, d 1.368, n 1.557. Washed with conc H2S04, water, aq 10% Na2C03 and water again, then dried with CaC12 and fractionally distd just before use. Phenethyl urea [2158-04-51 M 164.2, m 173-174O. Crystd from water. Phenetole [103-73-11 M 122.2, b 60°/9mm, 77.5°/31mm, 170.0°/760mm, d 0.967, n 1.50735, n25 1.50485. Small quantities of phenol can be removed by shaking with NaOH, but this is not a very likely contaminant of commercial material. Fractional distn from sodium, at low pressures, probably gives adequate purification. It can be dissolved in ethyl ether and washed with 10% NaOH (to remove phenols), then water. The ethereal soln was evaporated and the phenetole fractionally distd under vacuum. Phenocoll hydrochloride @-phenetidine HCI) [536-10-61 M 230.7, m 234O. Crystd from water. Sublimes in vacuo. Phenol [108-95-21 M 94.1, m 40.9O, b 85.5-86.0°/20mm, 180.8°/760mm, d 1.06, n41 1.54178, n46 1.53957. Steam was passed through a boiling soln containing lmole of phenol and 1.52.0moles of NaOH in 5L of H20 until all non-acidic naterial had distd. The residue was cooled, acidified with 20% (v/v) H2SO4, and the phenol was separated, dried with CaS04 and fractionally distd under reduced pressure. It was then fractionally crystd several times from its melt, [Andon et al. JCS 5246 19601. Purification via the benzoate has been used by Berliner, Berliner and Nelidow [JACS 76 507 19541. The benzoate was crystd from 95% EtOH, then hydrolysed to the free phenol by refluxing with two equivalents of KOH in aq EtOH until the soln became homogeneous. It was acidified with HCl and extracted with ethyl ether. The ether layer was freed

300

Purification of Organic Chemicals

from benzoic acid by thorough extraction with aqueous NaHC03, and, after drying and removing the ether, the phenol was distd. Phenol has also been crystd from a 75% w/w soln in water by cooling to 1l o and seeding with a crystal of the hydrate. The crystals were centrifuged off, rinsed with cold water (0-2O) satd with phenol, and dried. It can be crystd from pet ether [Berasconi and Paschalis JACS 108 2969 19861. Draper and Pollard [Science 109 448 19491 added 12% water, 0.1% aluminium (can also use zinc), and 0.05% NaHC03 to phenol, and distd at atmospheric pressure until the azeotrope was removed, The phenol was then distd at 25mm. Phenol has also been dried by distn from the benzene soln to remove the water-benzene azeotrope and the excess benzene, followed by distn of the phenol at reduced pressure under nitrogen. Processes such as this are probably adequate for analytical grade phenol which has as its main impurity water. Phenol has also been crystd from pet etherhenzene or pet ether (b 40-60°). Purified material is stored in a vacuum desiccator over P2O5 or CaS04.

Phenol-2,4-disulphonic acid [96-77-51 M 254.2. Crystd from EtOH/ethyl ether Phenolphthalein [787-09-81 M 319.2, m 263O. Dissolved in EtOH (7ml/g), then diluted with eight volumes of cold water. Filtered. Heated on a water-bath to remove most of the alcohol and the pptd phenolphthalein was filtered off and dried under vacuum. Phenolphthalol [81-92-5] M 306.3, m 201-202O. Crystd from aqueous EtOH. Phenosafranine [81-93-61 M 322.8,

A,,

530nm (HzO). Crystd from dilute HC1.

Phenothiazine [92-84-21 M 199.3, m 184-185O. Crystd from benzene or toluene (charcoal) after boiling for lOmin under reflux. Filtered on a suction filter. Dried in an oven at looo, then in a vacuum desiccator over paraffin chips. Also twice recrystd from water and dried in an oven at 100° for 8-10h. Phenoxazine [135-67-11 M 199.2, m 156O, 156-15S0, 158-159O, b 21S0/4mm. Crystd from EtOH and sublimed in vacuu. If too impure then extract in a Soxhlet using toluene. Evaporate the solvent and dissolve residue (ca 1OOg) in CgHg (1L) CARCINOGEN, use a good fumecupboard) and chromatograph through an A1203 column (50 x 450 mm). The eluent (ca 3L) is evaporated to ca 15Oml and cooled when ca 103g of phenoxazine m 149-153O is obtained. Sublimation yields platelets m 158-159O. It forms a green picrate m 141.5-142°. [Gilman and Moore JACS 79 3485 1957; Muller et al. JOC 24 37 19591. Phenoxyacetic acid [122-59-81 M 152.2, m 98-99O. Crystd from water or aqueous EtOH. Phenoxyacetyl chloride [701-99-51 M 170.6, b 112°/10mm, 102°/16mm, 225-226O/atm, diO 1.235, n i o 1.534. If it has no OH band i n the IR then distil in a vacuum, taking precutions for the moisture-sensitive copound. If it contains free acid (due to hydrolysis, OH bands in the IR) then add an equal volume of redistilled SOC12, reflux for 2-3h, evaporate and distil the residue is a vacuum as before. The amide has m 101O. [McElvain and Carney JACS 68 2592 19461. 4-Phenoxyaniline

[139-59-31 M 185.2, m 95O. Crystd from water.

Phenoxybenzamine (59-96-11 M 303.5, hydrochloride [63-92-31 M 340.0, m 137.5-140°. Crystd from EtOWethyl ether. 2-Phenoxybenzoic acid [2243-42-71 M 214.2, m 113O, b 3S0/760mm, 3-Phenoxybenzoic acid [3739-38-61 M 214.2, m 145O. Crystd from aqueous EtOH. Phenoxybutyric acid [6303-58-81 M 180.2, m 63-65O, 6 4 O , 65-66O, b 180-185°/12mm. It has been purified by recrystn from pet ether, C6H6, Et20-pet ether, EtOH and from H20. It can be distd in a good vac. [W:Ramart-Lucas and Hoch Bull Soc Chim France [4] 51 824 1932; Dann and Arndt A 587 38 19541. The acid chforide has b 154-156°/20mm [Hamford and Adams JACS 57 921 19353; and the amide crystallises from C6H6 as needles m 1 13O.

301

Purification of Organic Chemicals

2-Phenoxypropionic acid [940-31-81 M 166.2, m 115-116O, b 105-106°/5mm, 266O/758mm. Crystd from water.

265-

Phensuximide [86-34-01 M 189.2, m 71-73O. Crystd from hot 95% EtOH. Phenylacetamide [103-81-1] M 135.2, m 158.5O. Crystd repeatedly from absolute EtOH. Dried under vacuum over P2O5. Phenyl acetate [122-79-21 M 136.2, b 78°/10mm, d 1.079, n22 1.5039. Freed from phenol and acetic acid by washing (either directly or as a s o h in pentane) with aqueous 5% Na2C03, then with saturated aqueous CaC12, drying with CaS04 or Na2S04, and fractional distn at reduced pressure. Phenylacetic acid [103-82-21 M 136.2, m 76-77O, b 140-150°/20mm. Crystd from pet ether (b 40-60°), isopropyl alcohol, aq 50% EtOH or hot water. Dried under vac. It can be distd under reduced pressure. Phenylacetone [103-79-91 M 134.2, b 69-71°/3mm, d 1-00, n 1.516. Converted. to the semicarbazone and crystd three times from EtOH ( m 186-187O). The semicarbazone was hydrolysed with 10% phosphoric acid and the ketone was distd. [Kumler, Strait and Alpen JACS 72 1463 19501. Phenylacetonitrile

see benzyl cyanide.

[92-91-11 M 196.3, m 120.3-121.2O, b 196-210°/18mm. 4'-Phenylacetophenone EtOH. Can also be distd under reduced pressure.

Crystd from

Phenylacetylene [536-74-31 M 102.1, b 75O/80mm, d 0.930, n25 1.5463. Distd through a spinning band column. Should be filtered through a short column of alumina before use [Collman et al. JACS 108 2988 19861. dl-Phenylalanine [150-30-11 M 165.2, m 162O. Crystd from water and dried under vacuum over P2O5. L-Phenylalanine [63-91-21 M 165.2, m 280°(dec), [ c L ] D ~-34.0° ~ (c 2, HzO). Likely impurities are leucine, valine, methionine and tyrosine. Crystd from water by adding 4 volumes of EtOH. Dried under vac over P2O5. Also crystd from satd refluxing aq solns at neutral pH, or 1: 1 ( v h ) EtOWwater soln, or conc HCl. R -( +)- [5267-64- I ] S-(-)- [3182-95-41 Phenylalaninol (2-amino-3-phenylpropan-1-01) M 151.2, m 91-92O, 91.S0, 92-94O, b 80°/11mm (Kugelrohr), [(x]254O6 f28O, [a]2,0-25 f23-28.7O (c 1-5, EtOH). It can be recrystd from Et20 or CgH6-pet ether (b 40-60°) and distd in a vacuum. Has been purified by dissolving in Et20, drying over K2CO3, filtering, evaporating to a small volume , cooling in ice and collecting the plates. Store in the presence of KOH (i.e. CO2-free atm). [Karrer and Ehrhardt H C A 34 3203 1951; Oeda Bull Chem SOC Japan 13 465 19381. The picrate has m 141-141.5O (from EtOH-pet ether). The hydrogen oxalare has m 177O, 161-162O [Hunt and McHale JCS 2073 19-57]. The racemate has m 87-88O from CgH6-pet ether (75-77O from Et2O) , and the hydrochloride has m 139-141O [Fodor et al. JCS 1858 19511.

3-Phenylallyl chloride (cinnamyl chloride) [E: 18685-01-3112: 18684-06-11 M 152.6, b 9293O/3mm. Distd under vacuum three times from K2CO3. Phenyl 4-aminosalicylate

[133-11-91 M 229.2, m 153O. Crystd from isopropanol.

4-Phenylanisole [361-37-61 M 184.2, m 89.9-90.1O. Crystd from benzene/pet ether. vacuum in an Abderhalden pistol.

Dried under

9-Phenylanthracene [602-5-5-11 M 254.3, 153-154O. Chromatographed on alumina in benzene and crystd from acetic acid.

302

Purification of Organic Chemicals

N-Phenylanthranilic acid [91-40-7] M 213.2, 182-183O. Crystd from EtOH (5ml/g) or acetic acid (2ml/g) by adding hot water (1mVg).

2-Phenyl-l-azaindolizine [56983-95-01 M 194.2, m 140O. Crystd from EtOH or benzene/pet ether. p-Phenylazoaniline

see p-aminoazobenzene,

p-Phenylazobenzoyl chloride [104-24-51 M 244.7, m 93O. Crystd from pet ether (b 60-80°) 4-Phenylazodiphenylamine

see benzeneazodiphenylamine.

l-Phenylazo-2-naphthol (Sudan I) [842-07-91 M 248.3, m 131O. Crystd from EtOH.

4-Phenylazo-a-naphthylamine [I31-22-61 M 247.3. Crystd from cyclohexane. l-Phenylazo-2-napthylamine [85-84-71 M 247.3, m 99-looo. Crystd from absolute EtOH or glacial acetic acid. 4-Phenylazophenacyl bromide M 317.3, m 103-104O. Purified on a column of silica gel, using pet ethedethyl ether (9:1 v/v) as solvent. 4-Phenylazophenol

[1689-82-31 M 198.2, m 155O. Crystd from benzene or 95% EtOH.

Phenyl benzoate [93-99-21 M 198.2, m 69.S0, b 198-199O. Crystd from EtOH using ca twice the volume needed for complete soln at 6 9 O . Phenyl-1,4-benzoquinone [363-03-11 M 184.2, m 114-115O. Crystd from heptane or pet ether (b 60-70°) and sublimed in vacuo. [Carlson and Miller JACS 107 479 19851. N-Phenylbenzylamine

see benzylaniline.

l-Phenylbiguanide

[102-02-31 M 177.2, m 144-146O. Crystd from water or toluene.

Phenyl boric acid

(benzeneboronic acid)

see Chapter 4.

l-Phenyl-1,3-butanedione see benzoylacetone. S-(-)-l-Phenylbutanol [22135-49-51 M 150.2, m 46-47O, 46-48O, 49O, b 90-92O/2mm. [a];* -51.4O (c 5, CHCIJ), -44.7O (c 5.13, C6H6). Purified by distn and crystallises on cooling. The hydrochloride has [ago+45.1° (c 4.8, C&). The (-)-hydroperoxide has b 58°/0.005mm, n'; 1.5123, a;* -2.14O, (1 = 0.5, neat). [Holding and Ross JCVS 145 1954; Davies and Feld JCS 4637 19-58]. The (&)racemate has b 73O/O.O5mm, and its 4-nitrophenylhydrazonehas m 5 8 O . l-Phenylbutan-2-one Phenylbutazone

see benzyl ethyl ketone.

[50-33-91 M 308.4, m 105O. Crystd from EtOH.

trans-4-Phenyl-3-buten-2-onesee benzalacetone. 2-Phenylbutyramide [90-26-61 M 163.2, m 86O. Crystd from water. R - ( - ) - [937-79-41 and S - ( + ) - [4286-15-11 2-Phenylbutyric acid M 164.2, b 102-104°/atm, d:' 1.056, n$' 1.521, [ a ] k o ? 9 6 0 ( c 2.5, C6H6), [a]i3+95.8 (neat). Purified by distn at atmospheric pressure using an efficient column. The acid chlorides have b 106-107°/20mm, [aG8:8l08O (c 2,

303

Purification of Organic Chemicals

C6H6). [Levene et al. JBC 100 589 1933,Gold and Aubert HCA 41 1512 1958;ORD in heptane: Rothen and Levene JCP 7 975 19391. R - ( - ) - [772-14-51 a n d S-(+)- [772-15-61 3-Phenylbutyric acid M 164.2, b 94-95O/3mm, 134O/4mm, d:6 1.066, n i 5 1.5167, [ ~ x ] i ~ f 5 (c71,~C6H6). Purified as the 2-isomer above, i.e. by distn, but under a good vacuum. [Prelog and Scherrer HCA 42 2227 1959;Levene and Marker JBC 93 761 1932, 100 685 1933;Cram JACS 74 2137 19521. The R-amide crystallises from H20, m 101.5-102°, [a]:' -16.5O (c 1.2, EtOH). The racemic acid has m 39-40°, b 134-136O/6mm, 158O/12mm [Marvel et al. JACS62 3499 19401. 4-Phenylbutyric acid [1821-12-11M 164.2, m 50°. Crystd from pet ether (b 40-60°). o-(Phenylcarbamoy1)-1-scopolamine methobromide from 95% EtOH.

M 518.4, m 200.5-201S0(dec). Cry std

9-Phenylcarbazole [I 150-62-51M 243.3, m 94-95O. Crystd from EtOH or isopropanol and sublimed in vacuo. 0-Phenyl chlorothionoformate [1005-56-7] M 172.6, b 81-83°/6mm, 91°/10mm, dO : 1.276, nho 1.585. Purified by dissolving in CHC13, washing with H20, drying (CaC13), filtering, evaporating and distilling twice under vacuum to give a clear yellow liquid. It is reactive and POISONOUS work in a fumecopboard. Store in sealed ampoules under N2. Possible impurity is 0,O'-diphenyl thiocarbonate which has m 106O which remains behind in the distilling flask. [Bogemann et al. in Methoden Der Organischen Chemie (Houben-Weyl) 4th edn (E.Muller ed.) Vol 9 Schwefel-Selen-Tellur Verbindungen pp807-808 1955; Rivier and Schalch HCA 6 612 1932; Kalson B 20, 2384 1987; Rivier and Richard HCA 8 490 1925; Schonberg and Varga A 483 176 1930;B 64 1390 19311.

-

Phenyl cinnamate [2757-04-21 M 224.3, m 75-76O, b 205-207°/15mm. (2mVg). It can also be distd under reduced pressure. a-Phenylcinnamic acid ethedpet ether.

Crystd from EtOH

[91-48-51 M 224.3, m 174O(cis), m 138-139°(trans). Crystd from

a-Phenyl-p-cresol see p-benzylphenol. o-Phenylenediamine [95-54-51M 108.1, m 1OO-10lo. Crystd from aqueous 1% sodium hydrosulphite (charcoal), washed with ice-water and dried in a vacuum desiccator, or sublimed in vucuo. It has been purified by recrystn from toluene and zone refined [Anson et al. JACS 108 6593 19861. Purification by refluxing a CH2C12 solution containing charcoal was also carried out followed by evaporation and recrystn [Koola and Kochi JOC 52 4545 19871,protect from light. m-Phenylenediamine [108-45-21 M 108.1, m 61-63O, 62-63O, 62.85O, 63-64O, b 146O/22mm, 282-284°/760mm, 284-287O/atm, d i i 1.1422, n g . 7 1.6340. Purified by distn under vac followed by recryst from EtOH (rhombs) and if necessary redistn. It should be protected from light otherwise it darkens rapidly. [Neilson et al. JCS 371 1962;IR: Katritzky and Jones JCS 3674, 2058 1959;W: Forbes and Leckie Canad J Chem 36 1371 19581. The hydrochloride has m 277-278O, and the bis-4-chlorobenzenesulphonyl derivative has m 220-221O from H20 (214-215O, from MeOH-H20) [Runge and Pfeiffer B 90 1737 19571. p-Phenylenediamine [106-50-31M 108.1, m 140O. Crystd from EtOH or benzene, and sublimed in vucuo,protect from light. o-Phenylenediamine dihydrochloride [615-28-1]M 181.1, m 180O. Crystd from dilute HCl (60ml conc HCl, 40ml water, with 2g stannous chloride), after treatment of the hot soln with charcoal by adding an equal volume of conc HCl and cooling in an ice-salt mixture. The crystals were washed with a small amount of conc HCl and dried in a vacuum desiccator over NaOH.

304

Purification of Organic Chemicals

2-Phenyl-1,3-diaza-azulene[2161-31-I] M 187.5. Recrystd three times from de-aerated cyclohexane in the dark.

1,4-Phenylene diisothiocyanate (bitoscanate) [4044-65-91 M 192.3, rn 129-131°, 130-131°, 132O. Purified by recrystn from AcOH, pet ether (b 40-60°), Me2CO or aq Me2CO. [van der Kerk et al. Rec Trav Chim Pays Bas 74 1262 1955; Leiber and Slutkin J O C 27 2214 19621.

R-(-)- [16355-00-31 a n d S-(+)- [25779-13-91 l-Phenyl-1,2-ethanediol M 138.2, rn 64-67O, 65-66O, [a]? f40.5O (c 2.8, HzO), [a]i0+390 (c 3, EtOH). Purified by recryst from CgHg-ligroin and sublimed at 1-2mm. [Arpesella et al. Gazeffa 85 1354 1955; Prelog et al. H C A 37 221 19541. R-(+)- [33375-06-31 and S(-)- [14649-03-71 1-Penylethyl isocyanate M 147.2, b 82-83O/1214mm, d;O 1.045, n i o 1.513, [a]k4f-2' (c 3.5, CsHs), f10.5O (neat). Purified by fractional distn under vacuum. With ammonia it gives the ureido derivative which crystallises from H20, m 121-122O, [ag5 f48.8O. [Cairns J A C S 63 870 19411. The racemafe has b 90-94O/3mm, 96O/18mm [Seiftan A 562 75 19491. Phenyl disulphide

see diphenyl disulphide.

dZ- 1-Phenylethanol [13323-81-41 M 122, b 106-107°/22-23rnrn, d 1.01, n25 1.5254. Purified via its hydrogen phthalate. [See Houssa and Kenyon JCS 2260 19301. Shaken with a soln of ferrous sulphate, and the alcohol layer was washed with distilled water and fractionally distd.

2-Phenylethanol (60-12-81 M 122.1, b 215-217O, d 1.020. Purified by shaking with a soln of ferrous sulphate, and the alcohol layer was washed with distd water and fractionally distd. Phenyl ether [IOl-84-81 M 170.2, m 27.0°, d 1.074, n30*' 1.57596. Crystd from 90% EtOH. Melted, washed with 3M NaOH and water, dried with CaC12 and fractionally distd under reduced pressure. Fractionally crystd from its melt and stored over P2O5. p-a-Phenylethylphenol

[I 988-89-21 M 198.3, m 56.0-56.3O. Crystd from pet ether.

5-(a-Phenylethyl)sernioxamazide EtOH.

[93-95-81 M 207.1, m 167-168O (Z-), 157O (dZ-). Crystd from

9-Phenyl-3-fluorone [975-17-71 M 320.3, rn >300°(dec), ,,A 462nrn (E 4.06 x 104, in 1M HCI aq EtOH). Recrystd from warm, acidified EtOH by addition of ammonia. The crude material (lg) can be extracted with EtOH (5Oml) in a Soxhlet apparatus for lOhr to remove impurities. Impurities can be detected by paper electrophoresis. [Petrova et al. Anal Left 5 695 19721. L-a-Phenylglycine from EtOH.

[2935-35-51 M 151.2, rn 305-310°, [a1546 +185O (c 1, M HCI). C r y s t d

Phenylglycine-o-carboxylicacid [612-42-01 M 195.2, rn 208O. Crystd from hot water (charcoal). Phenylglyoxaldoxirne

see isonitrosoacetophenone.

Phenylhydrazine [IOO-63-01 M 108.1, m 23O, b 137-138°/18mm, 241-242°/760mm, d 1.10, n 1.607. Purified by chromatography, then crystd from pet ether (b 60-80°)/benzene. [Shaw and Stratton JCS 5004 19621. Phenylhydrazine hydrochloride [59-88-1] M 144.5, rn 244O. One litre of boiling EtOH was added to lOOg of phenylhydrazine hydrochloride dissolved during 1-3h (without heating) in 2OOml of warm water (607 0 O ) . The s o h was filtered off, while still hot, through Whatman No 2 filter paper and cooled in a refrigerator. The ppte was collected on a medium sintered-glass filter and recrystd twice this way, then washed with cold

Purification of Organic Chemicals

305

EtOH, dried thoroughly and stored in a stoppered brown bottle. [Peterson, Karrer and Guerra AC 29 144 39573. Hough, Powell and Woods [JCS 4799 19561 boiled the hydrochloride with three times its weight of water, filtered hot (charcoal), added one-third volume of conc HC1 and cooled to Oo. The crystals were washed with acetone, and dried over P2O5 under vacuum. The salt has also been crystd from 95% EtOH. Phenylhydroxylamine [IOO-65-21 M 109.1, m 82O. Crystd from water 2-Phenyl-1,3-indandione [83-12-51 M 222.2, m 149-151°, 2-Phenylindolizine [25379-20-81 M 193.2, m 214O(dec). Crystd from EtOH. Phenylisocyanate [103-71-91 M 119.1, b 45-47°/10mm, d 1.093, n 1.536. Distd under reduced pressure from P2O5. Phenylisothiocyanate (phenyl mustard oil) [ 1 0 3 - 7 2 - 0 1 M 135.2, m -21°, b 95O/12mm, 117.1°/33mm, 221°/760mm, d i 5 1.1288, nYe41.64918. It is insol in H20, but sol in Et2O and EtOH. If impure (due to formation of thiourea) then steam dist into a receiver containing 5-10ml of N H2SO4. Separate the oil, dry over CaC12 and distil under vacuum. [Dains et al. Org Synth Coll Vol I 447 19411. 3-Phenyllactic acid

see 2-hydroxy-3-phenylpropionic acid.

1-Phenyl-5-mercaptotetrazole [ 8 6 - 9 3 -I 1 M 178.2, m 150° (dec), 155O (dec), 157-158O. Purified by recryst from EtOH or CHC13 (m 152O), and has a pKa25 of 3.65 in 5 % aqueous EtOH. [Tautomerism: Kauer and Sheppard JOC 32 35801967; UV: Leiber et al. Canad J Chem 37 563 19591. The ammonium salt crystallises from EtOH and dec at 176O, and the sodium salt crystallises from EtOH-C6H6, melts at 96O and dec at 145O [Stollt J Prakt Chem [2]133 60 19321. Phenyl methanesulphonate [16156-59-51 M 172.1, m 61-62O. Crystd from MeOH. 2-Phenylnaphthalene [612-94-21 M 204.3, m 103-104O. Chromatographed on alumina in benzene and crystd from aqueous EtOH.

N-Phenyl-1-naphthylamine [90-30-21 M 219.3, m 63.7-64.0°. Crystd from EtOH, pet ether or benzeneEtOH. Dried under vacuum in an Abderhalden pistol. N-Phenyl-2-naphthylamine (135-88-61 M 219.3, m 107.5-108S0. Crystd from EtOH, MeOH, glacial acetic acid or benzenehexane. 4-Phenylphenacyl bromide [135-73-91 M 275.2, m 126O. Crystd (charcoal) from EtOH (15ml/g), or ethyl acetate/pet ether (b 90-10O0. 4-Phenylphenol (4-hydroxybiphenyl) [92-69-31 M 170.2, m 166-167O. Crystd from benzene, EtOH or EtOWwater, and vacuum dried in a desiccator over CaC12. [Buchanan et al. JACS 108 7703 19861. 2-Phenylpropanal [93-53-81 M 134.2, b 206°/760mm, d 1.001, n 1.5183. May contain up to 15% of acetophenone. Purified via the bisulphite addition compound [Lodge and Heathcock JACS 109 3353 1987. Phenyl-2-propanone

see phenylacetone.

Phenylpropiolic acid [637-44-51 M 146.2, m 137.8-138.4O. Crystd from benzene, CCl4 or aqueous EtOH. a-Phenylpropionic acid [492-37-51 M 150.2, m 49O. Crystd from pet ether (b 40-60°).

306

Purification of Organic Chemicals

R - ( - ) - [7782-26-51 a n d S-(+)- [7782-24-31 2-Phenylpropionic acid M 150.2, m 30.3-31°, 30-32O, b 121-123°/0.5mm, 115°/1-2mm, [a]L0k99.7O (I = 1, neat), k81° (c 1.7, EtOH), k73O (c 1.6, CHC13). Purified by vacuum distn and by recrystn from pet ether. The anilide has m 99-100°, [a]i0f1200(c 1.1, EtOH) [Fodor and Csepregly TET LETT no 7 p16 1959; Bernstein and Whitmore JACS 61 1324 19391. 3-Phenylpropyl bromide [637-59-21 M 199.1, b 110°/12mm, 128-129°/29mm, d 1.31. Washed successively with conc H2SO4, water, 10% aqueous Na2C03 and again with water, then dried with CaC12 and fractionally distd just before use. Phenyl 2-pyridyl ketoxime [1826-28-41 M 198.2, m 151-152O. Crystd from EtOH (charcoal). Phenylpyruvic acid [156-06-91 M 164.2, m 150-154O, 158-159O. Recrystd from C6H6. The phenylhydrazone has m 173O [Zeller HCA 26 1614 1943; Hopkins and Chisholm Canad J Research [B] 24 89 19461. The 2,4-dinitrophenylhydrazonehas m 162-164O (189O, 192-194O) [Fones JOC 17 19521. 6-Phenylquinoline [162-95-31 M 205.3, m 110.5-111.5° . Crystd from EtOH (charcoal).

2-Phenylquinoline-4-carboxylicacid 20ml/g).

[132-60-51 M 249.3, m 215O. Crystd from EtOH (c a

Phenyl salicylate [118-55-8] M 214.2, m 41.8-42.6O. Fractionally crystd from its melt, then crystd from benzene. 2-Phenylsalicylic acid [304-06-31 M 214.3, m 186-187.5O. Dissolved in ca 1 equivalent of saurated aqueous Na2C03, filtered and ppted by adding 0.8 equivalents of M HC1. Crystd from ethylene dichloride (charcoal), and sublimed at O.lmm. [Brooks, Eglington and Norman JCS 661 19611. 1-Phenylsemicarbazide [103-03-71 M 151.2, m 172O, 4-Phenylsemicarbazide [537-47-31 M 151.2, m 122O. Crystd from water and dried in vac over KOH.

R-(-)-[46292-93-71 a n d S - ( + ) - [4036-30-11 Phenylsuccinic acid M 194.2, m 173-176O, 178.5-179O, 179-180°, [a];' +171° (c 2, MeZCO), +148O (c 0.27-5, EtOH). Purified by repptn from alkali and recrystn from H20. [Naps and Johns JACS 62 2450 1940; Fredga and Matell Bull Soc Chirn Belges 62 47 1953; Wren and Williams JCS 109 572 19161. The racemate [635-51-81 has m 166-

168O, 168O after recrystn from H20 or MeCN and pKa25 values in H 20 of 3.78 and 5.55; its Sbenzylthiouroniurn salt has m 164-165O (from EtOH) [Griediger and Pedersen Acta Chern Scand 9 1425 19551.

l-Phenyl-5-sulphanilamidopyrazole [526-08-91 M 314.3, m 179-183O, l-Phenylthiosemicarbazide [645-48-71 M 167.2, m 200-201°(dec), 4-Phenylthiosemicarbazide (5351-69-91 M 167.2, m 140O. Crystd from EtOH. l-Phenyl-2-thiourea [103-85-51 M 152.1, m 154O. Crystd from water and dried at l0OOin air. Phenyltoloxamine hydrochloride methyl ketone. Phenyl 4-toluenesulphonate acetic acid.

[6152-43-81 M 291.8, m 119-120°. Crystd from isobutyl

[640-60-81 M 248.2, m 94.5-95.5O. Crystd from MeOH or glacial

Phenyl 4-tolylcarbonate [13183-20-51 M 228.2, m 67O. Purified by preparative GLC with 20% Apiezon on Embacel, and sublimed in vacuo. 4-Phenyl-l,2,4-triazole-3,5-diol [15988-11-11 M 175.2, m 207-209O. Crystd from water.

307

Purification of Organic Chemicals

R - ( - ) - [I0531-50-71 and S-(+)- [340-06-71 l-Phenyl-2,2,2-trifluoroethanolM 176.1, b 7476O/lOmm, 125-127°/760mm, d i 0 1.301, n i o 1.4632, [ a ] y & 3 l o(neat). Purified by fractional distn preferably in a vacuum. [Momson and Ridgeway TET LETT 573 1969;NMR: Pirkle and Beare JACS 90 6250 19681. The racemate [340-05-61has b 52-54O/2mm, 57-59O/2mrn, 64-65O/5rnm, di0 1.293, nko 1.457, and it 2-carbobenzoyl derivative has m 137-138O [Mosher et al. JACS 78 4374 19561.

4-Phenylurazole

see 4-phenyl-1,2,4-triazole-3,5-diol.

Phenylurea [64-10-81M 136.2, m 148O. Crystd from boiling water (10mUg). Dried in a steam oven at looo. 9-Phenyl-9-xanthenol (hydroxypixyl] [596-38-31M 274.3, m 158-161°, 158.5-159O, 159O. Dissolve in AcOH and add H20 whereby it separates as colourless prisms. It is slightly soluble in CHC13, soluble in C6H6 but insoluble in pet ether. It sublimes on heating. W in H2S04: hmax 450nm (E 5620) and 370nm ( E 24,900) and the HCf04 salt in CHC13 has hmax 450 ( E 404) and 375nm ( E 2420). [Sharp JCS 2558 1958;Bunzly and Decker B 37 2983 1904;Chattopadhyaya and Reece JCSCC 639 1978;Gomberg and Cone A 370 142 19091. Phloretic acid see 3-p-hydroxyphenylpropionic acid. Phloretin [60-82-21M 274.3, m 264-271°(dec). Crystd from aqueous EtOH. Phlorizin (2Hz0) [60-81-11M 472.5, m l l O o , from water.

[ ~ ~ ] 2 5 0 -62O 4 ~ (c 3.2, EtOH).

Crystd as dihydrate

Phloroacetophenone (2Hz0) [480-66-01M 186.2, m 218-219O. Crystd from hot water (35mVg). Phloroglucinol (2Hz0) [6099-90-71M 126.1, m 217-219O, 117O (anhydrous). water, and stored in the dark under nitrogen.

Crystd from

Phorone [504-20-11M 138.2, m 2S0, b 197O/743mm. Crystd repeatedly from EtOH. "Phosphine" (a dye, CI 793). Crystd from benzeneEtOH. Phthalaldehyde [643-79-81M 134.1, m 54-56O, 55.5-56O, 5S0, b 83-84°/0.8mm. Purified by steam distillation better by using super heated steam (at 175-180°) and efficient cooling. The distillate is saturated with Na2S04 extracted exhaustively with EtOAc, dried (Na2S04), filtered and evaporated. The residue is recrystd from pet ether (b 90-10O0) [Beill and Tarbell Org Synth Coll Vol IV 808 19631. It can be distd under vacuum. The bis-2,4-dinitrophenyfhydrazonehas m 278-280° [Hatt and Stephenson JCS 199 19521. Phthalazine (253-52-11M 130.2, m 90-91O. Crystd from ethyl ether or benzene, and sublimed under vacuum. Phthalazine-1,4-dione [1445-69-81M 162.2. Twice recrystd from 0.1M KOH [Merenyi et al. JACS 108 7716 19861. Phthalazone [119-39-11M 146.2, m 183-184O, b 337O/760mm. Crystd from water and sublimed in vacuo. Phthalein complexon [2411-89-41M 654.6. o-Cresolphthalein is a contaminant and is one of the starting materials. It can be removed by dissolving the reagent in water and adding a 3-fold excess of sodium acetate and fractionally precipitating it by dropwise addition of HCl to the clear filtrate. The pure material gives a single spot on paper chromatography (eluting solvenbEtOWwater/phenol, 6:3: 1;and developing with NaOH). [Anderre et al. HCA 37 113 19541.

308

Phthalhydrazide

Purification of Organic Chemicals

see phthalazine-1,4-dione.

o-Phthalic acid [88-99-31 M 166.1, m 211-211.5O. Crystd from water. Phthalic anhydride [85-44-91 M 148.1, m 132O, b 295O. Distd under reduced pressure. Purified from the acid by extraction with hot CHC13, filtered and evaporated. The residue was crystd from CHC13, CC14 or benzene. Fractionally crystd from its melt. Dried under vacuum at looo. [Saltiel JACS 108 2674 19861. Phthalide [87-41-21 M 134.1, m 72-73O. Crystd from water (75ml/g) and dried in air on filter paper. Phthalimide [85-41-61 M 147.1, m 235O. Crystd from EtOH (2Oml/g) (charcoal), or by sublimation. Phthalimide potassium salt (potassium phthalimide) [1074-82-41 M 185.2, m >300°. The solid may contain phthalimide and K2CO3 from hydrolysis. If too much hydrolysis has occurred (this can be checked by extraction with cold Me2CO in which the salt is insoluble, evaporation of the Me2CO and weighing the residue) then it would be better to prepare it afresh. If little hydrolysis had occurred then recryst from a large vol of EtOH, and wash solid with a little Me2CO and dry in a continuous vac to constant weight. [Salzerg and Supriawski Org Synth Coll Vol I 119 1941; Raman and IR: Hase J Molecular Structure 48 33 1978; Dykman Chemistry and Industry (London) 40 1972; IR, NMR: Assef et al. Bull SOCChim France I1 167 19791. Phthalimidoglycine

[4702-13-01 M 205.2, m 192-193O. Crystd from water or EtOH.

Phthalonitrile [91-15-61 M 128.1, m 141O. Crystd from EtOH or benzene. Can also be distd under high vacuum. Phthalylsulphacetamide

[131-69-11 M 362.3, m 196O. Crystd from water.

Phthiocol [483-55-61 M 188.1, m 173-174O. Crystd from ethyl ethedpet ether. Physalien [144-67-21 M 1044, m 98.5-99S0, &Il: 1410 (449nm), 1255 (478nm) in hexane. Purified by chromatography on water-deactivated alumina, using hexane/ethyl ether (19: 1) to develop the column. Crystd from benzeneEtOH. Stored in the dark, in inert atmosphere, at Oo. Physostigmine (Eserine) [57-47-61 M 275.4, m 105-106O, [ c L I ~ ~-91O O ~ ~ (c 1.7, CHCl3). Crystd from ethyl ether or benzene. Phytoene [540-04-51 M 544.9, :E: 850 (287nm) in hexane, h,,, 275, 287 and 297nm nm. Purified by chromatography on columns of magnesia-Supercel or alumina [Rabourn et al. Arch Biochem Biophys 48 267 19541. Stored as a solution in pet ether under nitrogen at -2OO. Phytofluene [27664-65-91 M 542.9, E:% , 1350 (348nm) in pet ether, h,,, 331, 348, 267. Purified by chromatography on partially deactivated alumina [Kushwaha et al. JBC 245 4708 19701. Stored as a s o h in pet ether under nitrogen at -2OO. Picein [530-14-31 M 298.3, m 195-196O. Crystd from MeOH or (as monohydrate) from water. Picene [213-14-3] M 278.3, m 364O. Crystd from isopropylbenzene/xylene. Can also be sublimed. Picoline see met h y lp y ridi ne. 2-Picoline-N-oxide (2-methylpyridine l-oxide) [ 9 3 1 - 1 9 - 1 1 M 109.1, m 41-45O, b 8990°/0.8-0.9mm, 90-100°/lmm, 110°/4mm, 135O/5mm, 123O/9mrn, 123-124O/15mm, 25926 1°/atm, nL5 1.5854 (supercooled). Purified by fractional distillation and could be recrystd from C6H6hexane but is hygroscopic. [Bullitt and Maynard JACS 76 1370 1954; Ross et al. JACS 78 3625 1956; IR: Wiley and SlaymAker JACS 79 2233 1953. The picrute has m 125-126.5O (from EtOH) [Boekelheide and

Purification of Organic Chemicals

309

Linn JACS 76 1286 19541. The phthalate has m 115-116O (from EtOH) [den Hertog et al. Rec Trav Chim Pays Bas 70 591 19511. 3-Picoline-N-oxide (3-methylpyridine 1-oxide) [ 1003-73-21 M 109.1, m 37-39O, 37-38O (evac capillary) , 84-85O/0.3mm, 101-103°/0.7-0.8mm, 114-115°/1.5mm, 118O/2m m . Purified by careful fractionation in vacuo. The distillate remains supercooled for several days before solidifying. It is a slightly hygroscopic solid which could melt in the hand. It has a pKa25 if 1.08 in H20. The picrate has m 149-151O (from EtOH). [Taylor and Corvetti Org Synth Coll Vol IV 654 1963; IR: Katritzky et al. JCS 3680 1959; Jaff6 and Doak JACS 77 4441,4481 1955; Boekelheide and Linn JACS76 1286 19541. 4-Picoline-N-oxide (4-methylpyridine 1-oxide) [ f 003-67-41 M 109.1, m 182-184O, 185186O, 186-188O. Recryst from EtOH-EtOAc, or C6H6. [Bullitt and Maynard JACS 76 1370 1954; Boekelheide and Linn JACS 76 1286 19541. Picolinic acid [98-98-61 M 123.1, m 1 3 8 O . Crystd from water or benzene. a-Picolinium chloride [14401-91-31 M 129.6, m 200O. 1:1 Mixture of a-picoline and HCl, distd at 275O. Then vacuum sublimed at 91-9 1So. N-Picolinoylbenzimidazole M 173.3, m 105-107O. Recrystd three times from hexane [Fife and Przystas JACS 108 4631 19861. Picric acid [88-89-11 M 229.1, m 122-123O. Crystd first from acetic acid then acetone, toluene, CHC13, aqueous 30% EtOH, 95% EtOH, MeOH or H20. Dried in a vacuum oven at 80° for 2h. Alternatively, dried over Mg(C104)2 or fused and allowed to freeze under vacuum three times. Because it is EXPLOSIVE, picric acid should be stored moistened with H20, and only small portions should be dried at any one time. The dried acid should NOT be heated. Picrolonic acid (picrolic acid) [550-74-31 M 264.2, m 120°(dec),116.50 (dec at 125O) 125O. Crystd from water or EtOH (Solubility is 0.123% at 15O and 1.203% at looo in H20; and 1.107% at Oo and 11.68% at 8 1 O in EtOH). It forms Ca, Cu and Pb complexes [Maquestian et a1 Bull Soc Chim Belges 82 233 1973; Isaki et al. B 74 1420 19411. Picrotoxin [124-87-81 M 602.6, m 203O,

-40° (c 1, EtOH). Crystd from water.

Picryl chloride [88-8801 M 226.3, m 8 3 O . Crystd from CHC13 or EtOH. Picryl iodide [4436-27-51 M 340.0, m 164-165O. Crystd from benzene. Pimelic acid [lll-16-01 M 160.2, m 105-106O. Crystd from water or from benzene containing 5% ethyl ether. Pinacol (hexahydrate) [609f -58-31 M 194.3, m 46S0, b 59O/4mm. Distd then crystd repeatedly from water. Pinacol (anhydrous) [76-09-51 M 118.1, m 41.1°, b 172O. The hydrate is rendered anhydrous by azeotropic distn of water with benzene. Recrystd from benzene or toluene/pet ether, absolute EtOH or dry ethyl ether. Recrystn from water gives the hexahydrate. Pinacolone oxime [2475-93-61 M 115.2, m 78O. Crystd from aqueous EtOH. Pinacyanol chloride [2768-90-31 M 388.9, m 270°(dec). Crystd from EtOWethyl ether. R-a-Pinene [7785-70-81 M 136.2, b 61°/30mm, 1.4658, [a];’ +47.3O,

156.2°/760mm, d 0.858, nl’ 1.4634, n

310

Purification of Organic Chemicals

S-a-Pinene [7785-26-41 M 136.2, b 155-156°/760mm, d 0.858, n 1.4634, [a];' -47.2O. Isomerised by heat, acids and certain solvents. Should be distd under reduced pressure under nitrogen and stored in the dark. Purified via the nitrosochloride [Waterman et al. Rec Trav Chim Pays-Bas 48 1191 19291. For purification of optically active forms see Lynn [JACS 91 361 19191. Small quantities (0.5ml) have been purified by GLC using helium as carrier gas and a column at 90° packed with 20 wt% of polypropylene sebacate on a Chromosorb support. Larger quantities were fractionally distd under reduced pressure in a column packed with stainless steel gauze spirals. Material could be dried with CaH2 or sodium, and stored in a refrigerator: CaS04 and silica gel were not satisfactory because they induced spontaneous isomerisation. [Bates, Best and Williams JCS 1521 19621. dl-Pipecolinic acid [4043-87-21 M 129.1, m 264O. Crystd from water. Piperazine [110-85-0] M 86.1, m 110-112°,44O (hexahydrate 142-63-2) b 125-130°/760mm. Crystd from EtOH or anhydrous benzene, and dried at 0.Olmm. It can be sublimed under vacuum and purified by zone melting.

Piperazine-N,N'-bis(2-ethanesulphonic acid) (PIPES) [5625-37-61 M 302.4. Crystd from boiling water (maximum solubility is about 1gL) or as described for ADA, pKa20 7.85. Piperazine dihydrochloride ( H 2 0 ) [6094-40-21 M 177.1, m 82.5-83.5O. Crystd from aqueous EtOH. Dried at 1loo Piperazine-2,5-dione

[106-57-01 M 114.1, m 309-310°. Crystd from water

Piperazine phosphate (H20) [18534-18-41 M 197.6. Crystd twice from water, air-dried and stored for several days over Drierite. The salt dehydrates slowly if heated at 700. Piperic acid [136-72-11 M 218.2, m 217O. Crystd from EtOH. Protect from light. Piperidine [IIO-89-41 M 85.2, f.p. -9O,b 35.4°/40mm, 106°/760mm, d 0.862, n 1.4535, n25 1.4500. Dried with BaO, KOH, CaH2, or sodium, and fractionally distd (optionally from sodium, CaH2, or P2O5). Purified from pyridine by zone melting. dl-Piperidine-2-carboxylic acid

see pipecolinic acid.

Piperidinium hydrochloride [6091-44-71 M 121.6, m 244-245O. Crystd from EtOH/ethyl ether in the presence of a small amount of HCI. Piperidinium nitrate [6091-45-81 M 145.2, m llOo. Crystd from acetone/ethyl acetate. Piperine [94-62-21 M 285.4, m 129-129.5O. Crystd from EtOH or benzenenigroin. Piperonal [120-57-01 M 150.1, m 37O, b 140°/15mm, 263O/760mm. Crystd from aqueous 70% EtOH or EtOWwater. Piperonylic acid [94-53-11 M 166.1, m 229O. Crystd from EtOH or water. Pivalic acid (trimethylacetic acid) [75-98-91 M 102.1, m 35.4O, b 71-73O/O.1 m m . Fractionally distd under reduced pressure, then fractionally crystd from its melt. Recrystd from benzene. Pivaloyl chloride (trimethylacetyl chloride) [3282-30-21 M 120.6, b 57.6O/150mm, 70-.571/250mm, 104°/754mm, 104-105°/atm, 105-10So/atm, diO1.003, n'; 1.4142. First check the IR to see if OH bands are present. If absent, or present in small amounts, then redistil under moderate vac. If present in large amounts then treat with oxalyl chloride or thionyl chloride and reflux for 2-3h, evap and distil

31 1

Purification of Organic Chemicals

-

residue. Strongly LACHRYMATORY work in a fumecupboard. Store in sealed ampoules under N2. [Traynham and Battiste JOC 22 1551 1957; Grignard reactns: Whitmore et al. JACS 63 647 19411. Pixy1 chloride see 9-chloro-9-phenylxanthene. Plumbagin [481-42-51 M 188.1, m 78-79O. Crystd from aqueous EtOH. Polyacrylonitrile [25014-41-91. Ppted from dimethylformamide by addition of MeOH. Polybrene

see 1,5-Dimethyl-1,5-diazaundecamethylene polymethobromide.

Poly(diallyldimethylammonium) chloride. Ppted from water i n acetone, and dried in vacuum for 24h. [Hardy and Shriner JACS 107 3822 19851. Polyethylene [9002-88-41. Crystd from thiophen-free benzene and dried over P2O5 under vacuum. Polygalacturonic acid

see pectic acid.

Polymethyl acrylate [9002-21-81. Ppted from a 2% s o h in acetone by addition of water. Polystyrene [9003-53-61. Ppted repeatedly from CHC13 or toluene soln by addition of MeOH. Dried in vacuo [Miyasaka et al. JPC 92 249 19881. Polystyrenesulphonic acid (sodium salt) [25704-18-11. Purified by repeated pptn of the sodium salt from aqueous s o h by MeOH, with subsequent conversion to the free acid by passage through an Amberlite IR120 ion-exchange resin. [Kotin and Nagasawa JACS 83 1026 19611. Also purified by passage through cation and anion exchange resins in series (Rexyn 101 cation exchange resin and Rexyn 203 anion exchange resin), then titrated with NaOH to pH 7. The sodium form of polystyrenesulphonic acid ppted by addition of 2-propanol. Dried in a vac oven at 80° for 24h, finally increasing to 120° prior to use. [Kowblansky and Ander JPC 80 287 19761. Polyvinyl acetate [9003-20-71. Ppted from acetone by addition of n-hexane. Poly(N-vinylcarbazole) [25067-59-81. Ppted seven times from tetrahydrofuran with MeOH, with a final freeze-drying from benzene. Dried under vacuum. Polyvinyl chloride [9002-81-21, Ppted from cyclohexanone by addition of MeOH. Poly(4-vinylpyridine) [25232-41-11 M (105.1)n. Purified by repeated pptn from solns in EtOH and dioxane, and then EtOH and ethyl acetate. Finally, freeze-dried from tert-butanol. Poly(N-vinylpyrrolidone) [9003-39-81 M ( l l l . l ) n , crosslinked [25249-54-11 m >300°. Purified by dialysis, and freeze-dried. Also by pptn from CHC13 soln by pouring into ether. Dried in a vacuum over P2O5. For the crosslinked polymer purification is by boiling for lOmin in 10% HCI and then washing with glass-distilled water until free from C1 ions. Final C1 ions were removed more readily by neutralising with KOH and continued washing. Pontacyl Carmine 2G [3734-67-61 M 510.4, Pontacyl Light Yellow GX [6359-98-41 M 552.3. Salted out three times with sodium acetate, then repeatedly extracted with EtOH. See Chlorazol Sky Blue FF. [McGrew and Schneider JACS 72 2547 19.501. ~ dioxane), Prednisone [53-03-21 M 358.5, m 238O(dec), [ 0 r ] ~ ~ + 1 6(c8 1, 4.18) in MeOH. Crystd from acetonehexane. Pregnane [24909-91-91 M 300.5, m 83S0, ~[':r]

,A

238nm (log

+21° (CHC13). Crystd from MeOH.

E

312

Purification of Organic Chemicals

5P-Pregnane-3a,20a-diol [80-92-21 M 320.5, m 243-244O, [a]:!6 from acetone.

+31° (c 1, EtOH). C r y s t d

5P-Pregnane-3a,20P-diol [80-91-11 M 320.5, m 244-246O, [a]:!6 from EtOH.

+22O (c 1, EtOH). C r y s t d

Pregnenolone Prehnitine

see 3P-hydroxy-5-pregnen-20-one.

see 1,2,3,4-trimethylbenzene.

Procaine [59-46-11 M 236.3, m 51O (dihydrate), 61° (anhydrous). Crystd as the dihydrate from aqueous EtOH and as anhydrous material from pet ether or ethyl ether. The latter is hygroscopic. Proclavine (3,6-diaminoacridine) [92-62-61 M 209.2, m 284-286O. Crystd from aqueous MeOH. Prodiene see allene. Proflavine see 3,6-diaminoacridine hydrochloride. Progesterone [57-83-01 M 314.5, m 128S0, [a]!:6 +220° (c 2, dioxane). Crystd from EtOH. When crystd from pet ether m is 121°, A,,a 240nm, log E 4.25 (EtOH). L-Proline [147-85-31 M 115.1, m 215-220°(dec)(D-isomer), 220-222O(dec) (L-form), 205°(dec)(DL-isomer), [ a ](H20, ~ ~L-isomer). ~ Likely impurity are hydroxyproline. Purified via its picrate which was crystd twice from water, then decomposed with 40% H2SO4. The picric acid was extracted with ethyl ether, the H2SO4 was pptd with Ba(OH)2, and the filtrate evapd. The residue was crystd from hot absolute EtOH [Mellan and Hoover JACS 73 3879 19.511 or EtOWether. Hygroscopic. Stored in a desiccator. Prolycopene (2361-24-21 M 536.5, m 11l0,Amax 443.5, 470nm in pet ether. Purified by chromatography on deactivated alumina [Kushwaha et al. JBC 245 4708 19701. Crystd from pet ether. Stored in the dark, in an inert atmosphere at -2OO. L-Prolylglycine [2578-57-61 M 172.2. Crystd from water at 50-60° by addition of EtOH. 408, 432, 461 nm, E~',: 2040 (432nm) in Proneurosporene [10467-46-61 M 538.9, h,,, hexane. Purified by chromatography on deactivated alumina [Kushwaha et al. JBC 245 4708 19701. Stored in the dark, in an inert atmosphere at Oo. Propane [74-98-61 M 44.1, m -189.7, b -42.1°/760mm, d 0.5005, n 1.2898. Purified by bromination of the olefinic contaminants. Propane was treated with bromine for 30min at Oo. Unreacted bromine was quenched, and the propane was distd through two -78O traps and collected at -196O [Skell et al. JACS 108 6300 19861. Propane-1,2-diamine [78-90-01 M 74.1, b 120.S0, d 0.868, n 1.446. Purified by azeotropic distn with toluene. [Horton, Thomason and Kelly AC 27 269 19551. Propane-1,2-diol [57-55-61 M 76.1, b 104°/32mm, d 1.040, n 1.433. decanted and distd under reduced pressure.

Dried with Na2S04,

Propane-1,3-diol [504-63-21 M 76.1, b 110-122°/12mm, d 1.053, d 8 0 5 1.4398. Dried with K2CO3 and distd under reduced pressure. More extensive purification involved conversion with benzaldehyde to 2-phenyl-l,3-dioxune(m 47-48O) which was subsequently decomposed by shaking with 0.5M HC1(3ml/g) for 1Smin and standing overnight at room temperature. After neutralisation with K2CO3, the benzaldehyde was removed by distn and the diol was recovered from the remaining aqueous soln by continuous extraction with

313

Purification of Organic Chemicals

CHC13 for lday. The extract was dried with K2C03, the CHC13 was evaporated and the diol was distd. [Foster, Haines and Stacey TET 6 177 19611.

Propane-1-thiol [I 120-71-41 M 76.1, b 65.3°/702mm, d25 0.83598, n25 1.43511, Propane-2-thiol [75-33-21 M 76.1, b 49.8O/696mm, d25 0.80895, n25 1.42154. Purified by soln in aqueous 20% NaOH, extraction with a small amount of benzene and steam distn until clear. After cooling, the soln was acidified slightly with 15% H2SO4, and the thiol was distd out, dried with anhydrous CaS04 or CaC12, and fractionally distd under nitrogen. [Mathias and Filho JPC62 1427 19581. Also purified by liberation of the mercaptan by adding dilute HCI to the residue remaining after steam distn. After direct distn from the flask, and separation of the water, the mercaptan was dried (Na2S04) and distd under nitrogen.

1,2,3-Propanetricarboxylic acid

see tricarballic acid.

Propan-1-01 see n-propyl alcohol. Propan-2-01 see

isopropyl alcohol.

Propargyl alcohol [107-19-71 M 56.1, b 54O/57mm, 113.6°/760mm, d 0.947, n 1.432. Commercial material contains a stabiliser. An aqueous soln of propargyl alcohol can be concentrated by azeotropic distn with butanol or butyl acetate. Dried with K2CO3 and distd under reduced pressure, in the presence of about 1% succinic acid, through a glass helices-packed column. Propene [115-07-11 M 42.1, m -185.2O, b -47.8°/750mm, d 0.519, n-71 1.357. freeze-pump-thaw cycles and trap-to-trap distn.

Purified

by

p-(1-Propeny1)phenol [539-12-81 M 134.2, m 93-94O. Crystd from water. P-Propiolactone [57-57-81 M 72.1, b 83O/45mm, d 1.150, n25 1.4117. Fractionally distd under reduced pressure, from sodium. CARCINOGEN. Propionaldehyde [123-38-61 M 58.1, b 48.5-48.7O, d 0.804, n 1.3733, n25 1.37115. D r i e d with CaS04 or CaC12, and fractionally distd under nitrogen or in the presence of a trace of hydroquinone (to retard oxidation). Blacet and Pitts [JACS 74 3382 19521 repeatedly vacuum distd the middle fraction until no longer gave a solid polymer when cooled to -8OO. It was stored with CaS04. Propionamide [79-05-01 M 73.1, m 79.8-80.8O. Crystd from acetone, benzene, CHC13, water or acetone/water, then dried in a vacuum desiccator over P2O5 or conc H2SO4. Propionic acid [79-09-41 M 74.1, b 141°, d 0.992, n 1.3865, n25 1.3843. Dried with Na2S04 or by fractional distn, then redistd after refluxing with a few crystals of KMnO4. An alternative purification uses the conversion to the ethyl ester, fractional distn and hydrolysis. [Bradbury JACS 74 2709 19.521. Propionic acid can also be heated for 0.5h with an amount of benzoic anhydride equivalent to the amount of water present (in the presence of CrO3 as catalyst), followed by fractional distn. [Cham and Israel JCS 196 19601. Propionic anhydride [123-62-61 M 130.2, b 67°/18mm, Shaken with P2O5 for several nimutes, then distd.

168°/780mm, d 1.407, n 1.012.

Propionitrile [107-12-01 M 55.1, b 97.2O, d 1.407, n15 1.36812, n30 1.36132. Shaken with 1 : j dil HCI, or with conc HCl until the odour of isonitrile has gone, then washed with water, and aqueous K2CC3. After a preliminary drying with silica gel or Linde type 4A molecular sieves, it is stirred with CaH2 until hydrogen evolution ceases, then decanted and distd from P2O5 (not more than SgL, to minimise gel formation). Finally, it is refluxed with, and slowly distd from CaH2 (5g/L), taking precautions to exclude moisture. n-Propyl acetate [109-60-41 M 102.1, b 10ISO,d 0.887, n 1.38442. Washed with satd aqueous NaHC03 until neutral, then with satd aqueous NaCl. Dried with MgS04 and fractionally distd.

314

Purification of Organic Chemicals

n-Propyl alcohol [71-23-81 M 60.1, b 97.2O, dZ50.79995, n 1.385. The main impurities in n propyl alcohol are usually water and 2-propen- 1-01, reflecting the commercial production by hydration of propene. Water can be removed by azeotropic distn either directly (azeotrope contains 28% water) or by using a ternary system, e.g. by adding benzene. Alternatively, for gross amounts of water, refluxing over CaO for several hours is suitable, followed by distn and a further drying. To obtain more nearly anhydrous alcohol, suitable drying agents are firstly NaOH, CaS04 or K2CO3, then CaH2, aluminium amalgam, magnesium activated with iodine, or a small amount of sodium. Alternatively, the alcohol can be refluxed with npropylsuccinate or phthalate in a method similar to the one described under EtOH. Ally1 alcohol is removed by adding bromine (15mlL) and then fractionally distilling from a small amount of K2CO3. Propionaldehyde, also formed in the bromination, is removed as the 2,4-dinitrophenylhydrazone. n-Propyl alcohol can be dried down to 20ppm of water by passage through a column of pre-dried molecular sieves (type A, K+ form, heated for 3h at 3000) in a current of nitrogen. Distn from sulphanilic or tartaric acids removes impurities. Albrecht [JACS 82 38 13 19601 obtained spectroscopically pure material by heating with charcoal to 50-60°, filtering and adding 2,4-dinitrophenylhydrazineand a few drops of conc H2SO4. After standing for several hours, the mixture was cooled to 00, filtered and vac distd. Gold and Satchel1 [JCS 1938 19631 heated n-propyl alcohol with 3-nitrophthalic anhydride at 76-1 loo for 15h, then recrystd the resulting ester from H20, benzene/pet ether (b 100-120°)(3:1), and benzene. The ester was hydrolysed under reflux with aq 7.5M NaOH for 45min under nitrogen, followed by distn (also under nitrogen). The fraction (b 87-92O) was dried with K2CO3 and stirred under reduced pressure in the dark over 2,4-dinitrophenylhydrazine,then freshly distilled. Also purified by adding 2g NaBH4 to 1.5L alcohol, gently bubbling with argon and refluxing for lday at 50°. Then added 2g of freshly cut sodium (washed with propanol) and refluxed for one day. Distd, taking the middle fraction [Jou and Freeman JPC 81 909 19771. n-Propylamine [107-10-81 M 59.1, b 48S0, d 0.716, n 1.38815. Distd from zinc dust, at reduced pressure, in an atmosphere of nitrogen. n-Propyl bromide. [106-94-51 M 123.0, b 71.0°, d 1.354., n15 1.43695, nZ5 1.43123. Likely contaminants include n-propyl alcohol and isopropyl bromide. The simplest purification procedure uses drying with MgS04 or CaC12 (with or without a preliminary washed of the bromide with aq NaHC03, then water), followed by fractional distn away from bright light. Chien and Willard [JACS 79 4872 1953 bubbled a stream of oxygen containing 5 % ozone through n-propyl bromide for 1h, then shook with 3% hydrogen peroxide soln, neutralised with aq Na2C03, washed with distilled water and dried. Then followed vigorous stimng with 95% H2SO4 until fresh acid did not discolour within 12h. The propyl bromide was separated, neutralised, washed dried with MgS04 and fractionally distd. The centre cut was stored in the dark. Instead of ozone, Schuler and McCauley [JACS 79 821 1 9 5 7 added bromine and stored for 4 weeks, the bromine then being extracted with aq NaHS03 before the sulphuric acid treatment was applied. Distd. Further purified by preparative gas chromatography on a column packed with 30% SE-30 (General Electric ethylsilicone rubber) on 42/60 Chromosorb P at 150° and 4Opsi, using helium. [Chu JPC 41 226 19641. n-Propyl chloride [540-54-51 M 78.5, b 46.6O, d 0.890, n 1.3880. Dried with MgS04 and fractionally distd. More extensively purified using extraction with H2SO4 as for n-propyl bromide. Alternatively, Chien and Willard [JACS 75 6160 19531 passed a stream of oxygen containing about 5% ozone through the n-propyl chloride for three times as long as was needed to cause the first coloration of starch iodide paper by the exit gas. After washing with aqueous NaHCO3 to hydrolyse ozonides and remove organic acids, the chloride was dried with MgS04 and fractionally distd. 1 -Propyl-3-(p-chlorobenzenesulphonyl)urea aqueous EtOH.

[94-20-21 M 260.7, m 127-129O. Crystd from

Propylene carbonate [108-32-71 M 102.1, b 110°/0.5-lmm, 238-239O/76Omm, d 1.204, n 1.423. Manufactured by reaction of 1,2-propylene oxide with C02 in the presence of a catalyst (quaternary ammonium halide). Contaminants include propylene oxide, carbon dioxide, 1,2- and 1,3-propanediols, ally1 alcohol and ethylene carbonate. It can be purified by percolation through molecular sieves (Linde 5A, dried at 350° for 14h under a stream of argon), followed by distn under vac. [Jasinski and Kirkland AC 39 163 19671. It can be stored over molecular sieves under an inert gas atmosphere. When purified in this way it contains less

Purification of Organic Chemicals

315

than 2ppm water. Activated alumina and dried CaO have been also used as drying agents prior to fractional distn under reduced pressure. It has been dried with 3A molecular sieves and distd under nitrogen in the presence of p toluenesulphonic acid. Then redistilled and the middle fraction collected.

Propylenediamine Propyleneglycol

see propane-1,2-diamine. see propane- 1,2-diol.

dl-Propylene oxide [75-56-91 M 58.1, b 34S0, d 0.829, n 1.3664. Dried with Na2S04 or CaH2, and fractionally distd through a packed column (glass helices), after refluxing with Na, CaH2, or KOH pellets. n-Propyl ether [ I l l - 4 3 - 3 1 M 102.2, b 90.1°, d 0.740, nlS 1.38296, n 1.3803. Purified by drying with CaS04, by passage through an alumina column (to remove peroxides), and by fractional distn. Propyl formate [IIO-74-71 M 88.1, b 8 1 . 3 O , d 0.9058, n 1.3779. Distd, then washed with satd aq NaCI, and with satd aq NaHCO3 in the presence of solid NaCI, dried with MgS04 and fractionally distd. n-Propyl gallate [121-79-91 M 212.2, m 150O. Crystd from aqueous EtOH. n-Propyl iodide [107-08-41 M 170.0, b 102S0, d 1.745, n 1.5041. Should be distd at reduced pressure to avoid decomposition. Dried with MgS04 or silica gel and fractionally distd. Stored under nitrogen with mercury in a brown bottle. Prior to distn, free iodine can be removed by shaking with copper powder or by washing with aq Na2S203 and drying. Alternatively, the n-propyl iodide can be treated with bromine, then washed with aq Na2S203 and dried. See also n-bury1 iodide. n-Propyl propionate [106-36-51 M 120.2, b 122O, d 0.881, n 1.393. Treated with anhydrous CuSO4, then distd under nitrogen. 6-Propyl-2-thiouracil (propacil, propyail) I 5 1 4 2 - 5 1 M 170.2, m218-220°, 218-220°. Purified by recrystn from H 2 0 (sol in 900 parts at 20°, and 100 parts at 100O). U V , MeOH: hmax 277nm. [Anderson et al. JACS 67 2197 1945; Vanderhaegue Bull SOC Chim Belges 59 689 19501. Propyne [74-99-71 M 40.1, m -101So, b -23.2°/760mm, d-50 0.7062, n-40 1.3863. by preparative gas chromatography. 2-Propyn-1-01

Purified

see propargyl alcohol.

Protocatechualdehyde

[139-85-51 M 138.1, m 153O. Crystd from water or toluene.

Protopine [130-86-91 M 353.4, m 208O. Crystd from EtOWchloroform. Protoporphyrin

[553-12-81 M 562.7, m >300°. Crystd from ethyl ether.

Pseudocumene

see 1,2,4-trimethylbenzene.

S,S-Pseudoephedrine [90-82-41 M 165.2, m 118-119O, [a];' +53.0° (EtOH), +40.0° (H20). Crystd from dry ethyl ether, or from water and dried in a vacuum desiccator. Pseudoephedrine hydrochloride 1347-78-81 M 210.7, m 181-182O, Pseudoisocyanine iodide, Crystd from EtOH. Pteridine [91-18-91 M 132.2, m 139.5-140°. Crystd from EtOH, benzene, n-hexane, n-heptane or pet ether. It sublimes at 120-130°/20mm. Stored at Oo, in the dark; turns green in the presence of light. 2,4-( 1H,3H)-Pteridinedione (H20) [487-21-81 M 182.1, m >350°. Crystd from water.

316

Purification of Organic Chemicals

Pterin (2-aminopteridin-4(3H)-one) [2236-60-41 M 163.1, m >300°. It was dissolved in hot 1% aqueous ammonia, filtered, and an equal volume of hot 1M aqueous formic acid was added. The soln was allowed to cool at 0-2O overnight. The solid was collected and washed with distilledd water several times by centrifugation and dried in V ~ C U Oover P2O5 overnight, and then at 100° overnight. Pterocarpin [524-97-01 M 298.3, m 165O, [ a]:'

-220O. Crystd from EtOH.

Pteroic acid [119-24-41 M 312.3, m >300°(dec). Crystd from dilute HCI. It(+)-Pulegone [89-82-71 M 152.2, b 69S0/5mm, n 1.4849, d 0.935, Purified via the semicarbazone. [Erskine and Waight JCS 3425 19601.

[0(]2504~

+23.5O(neat).

Purine [120-73-01 M 120.1, m 216-217O. Crystd from toluene or EtOH. Purpurin [81-54-91 M 256.2, m 253-256O. Crystd from aqueous EtOH. Dried at looo. Purpurogallin [569-77-71 M 220.2, m 274O (rapid heating). Crystd from acetic acid. Pyocyanine [573-77-31 M 210.2, m 133O. Crystd from water. Pyrazine [290-37-91 M 80.1, m 47O, b 115.5-115.8O. Distd in steam and crystd from water. Purified by zone melting. Pyrazinecarboxamide water or EtOH.

[98-96-41 M 123.1, m 189-191O (sublimes slowly at 159O). Crystd from

Pyrazinecarboxylic acid [98-97-51 M 124.1, m 225-229O(dec). Crystd from water.

Pyrazine-2,3-dicarboxylic acid at 1W.

[89-01-01 M 168.1, m 183-185O(dec). Crystd from water.

Pyrazole [288-13-11 M 68.1, m 70°. Crystd from pet ether, cyclohexane, or water. JCSDT 2025 19861.

Pyrazole-3,5-dicarboxylic acid EtOH.

Dried

Barszcz et al.

[3112-31-0] M 174.1, m 287-289O(dec). Crystd from water or

Pyrene [129-00-01 M 202.3, m 149-150O. Crystd from EtOH, glacial acetic acid, benzene or toluene. Purified by chromatography of CC14 solns on alumina, with benzene or n-hexane as eluent. [Backer and Whitten JPC 91 865 1983. Also zone refined, and purified by sublimation. Marvel and Anderson [JACS 76 5434 19541 refluxed pyrene (35g) in toluene (4OOml) with maleic anhydride (5g) for 4days, then added 15Oml of aqueous 5% KOH and refluxed for 5h with occasional shaking. The toluene layer was separated, washed thoroughly with H20, concentrated to about lOOml and allowed to cool. Crystalline pyrene was filtered off and recrystd three times from EtOH or acetonitrile. [Chu and Thomas JACS 108 6270 1986; Russell et al. AC 50 2961 19861. The material was free from anthracene derivatives. Another purification step involved passage of pyrene in cyclohexane through a column of silica gel. It can be sublimed in a vacuum and zone refined. [Kano et al. JPC 89 3748 198.51. Pyrene-l-aldehyde [3029-19-41 M 230.3, m 125-126O. Recrystd three times from aqueous EtOH. l-Pyrenebutyric acid [3443-45-61 M 288.4, m 184-186O. Crystd from benzene, EtOH or EtOH/water (7:3 v/v). Dried over P2O5. [Chu and Thomas JACS 108 6270 19861.

l-Pyrenecarboxylic acid [3029-19-41 M 230.3, m 126-127O. Crystd from benzene or 95% EtOH.

Purification of Organic Chemicals

317

1-Pyrenesulphonic acid [26651-23-01 M 202.2. Crystd from EtOH/water.

1,3,6,8-Pyrenetetrasulphonic acid

[6528-53-61 M 522.2. Crystd from water.

Pyridine [110-86-1] M 79.1, f.p. -41.*, b 115.6O, d 0.9831, n 1.51021. Likely impurities are H 2 0 and amines such as the picolines and lutidines. Pyridine is hygroscopic and is miscible with H 2 0 and organic solvents. It can be dried with solid KOH, NaOH, CaO, BaO or sodium, followed by fractional distn. Other methods of drying include standing with Linde type 4A molecular sieves, CaH2 or LiAIH4, azeotropic distn of the H 2 0 with toluene or benzene, or treated with phenylmagnesium bromide in ether, followed by evaporation of the ether and distn of the pyridine. A recommended [Lindauer and Mukherjee PAC 27 267 19711 method dries pyridine over solid KOH (20g/Kg) for 2weeks, and fractionally distils the supernatant over Linde type 5A molecular sieves and solid KOH. The product is stored under C02-free nitrogen. Pyridine can be stored in contact with BaO, CaH2 or molecular sieves. Non-basic materials can be removed by steam distilling a s o h containing 1.2 equivalents of 20% H2SO4 or 17% HCl until about 10% of the base has been carried over along with the non-basic impurities. The residue is then made alkaline, and the base is separated, dried with NaOH and fractionally distd. Alternatively, pyridine can be treated with oxidising agents. Thus pyridine (800ml) has been stirred for 24h with a mixture of ceric sulphate (20g) and anhydrous K2C03 (15g), then filtered and fractionally distd. Hurd and Simon [JACS 84 4519 19621 stirred pyridine (135ml), water (2.5L) and KMnO4 (90g) for 2h at 100°, then stood for 15h before filtering off the ppted manganese oxides. Addition of solid KOH (ca 500g) caused pyridine to separate. It was decanted, refluxed with CaO for 3h and distd. Separation of pyridine from some of its homologues can be achieved by crystn of the oxalates. Pyridine is ppted as its oxalate by adding it to the stirred soln of oxalic acid in acetone. The ppte is filtered, washed with cold acetone, and pyridine is regenerated and isolated. Other methods are based on complex formation with ZnC12 or HgC12. Heap, Jones and Speakman [JACS 43 1936 19211 added crude pyridine (1L) to a soln of ZnC12 (8488) in 730ml of water, 346m1 of conc HCl and 690ml of 95% EtOH. The crystalline ppte of ZnCl2.2(pyridine) was filtered off, recrystd twice from absolute EtOH, then treated with a conc NaOH soln, using 26.78 of solid NaOH to l00g of the complex. The ppte was filtered off, and the pyridine was dried with NaOH pellets and distd. Similarly, Kyte, Jeffery and Vogel [JCS 4454 19601 added pyridine (60ml) in 300ml of 10% (v/v) HCI to a soln of HgC12 (405g) in hot water (2.3L). On cooling, crystals of pyridine-HgC12 (1:l) complex separated and were filtered off, crystd from 1% HCl (to m 178.5-179O), washed with a little EtOH and dried at 1 loo. The free base was liberated by addition of excess aq NaOH and separated by steam distn. The distillate was saturated with solid KOH, and the upper layer was removed, dried further with KOH, then BaO and distd. Another possible purification step is fractional crystn by partial freezing. Small amounts of pyridine have been purified by vapour-phase chromatography, using a 180-cm column of polyethyleneglycol-400 (Shell 5 % ) on Embacel (May and Baker) at looo, with argon as carrier gas. The Karl Fischer titration can be used for determining water content. A colour test for pyrrole as a contaminant is described by Biddiscombe et al. [JCS 1957 19541. Pyridine-2-aldehyde [ I 121-60-41 M 107.1, b 81S0/25mm, d 1.121, n 1.535, Pyridine-3-aldehyde [500-22-1] M 107.1, b 89S0/14mm, d 1.141, n 1.549, [872-85-51 M 107.1, b 79S0/12mm, d 1.137, n 1.544. Sulphur dioxide Pyridine-4-aldehyde was bubbled into a s o h of 50g in 250ml of boiled out water, under nitrogen, at Oo, until pptn was complete. The addition compound was filtered off rapidly and, after washing with a little water, it was refluxed in 17% HCI (200ml) under nitrogen until a clear s o h was obtained. Neutralisation with NaHC03 and extraction with ether separated the aldehyde which was recovered by drying the extract, then distilling twice, under nitrogen. [Kyte, Jeffery and Vogel JCS 4454 19601. Pyridine-2-aldoxime [873-69-81 M 122.1, m 113O, Pyridine-3-aldoxime [ I 193-92-61 M 122.1, m 150°, Pyridine-4-aldoxime [696-54-81 M 122.1, m 129O. Crystd from water Pyridine-2-carboxylic acid

see picolinic acid.

Pyridine-3-carboxylic acid

see nicotinic acid.

318

Purification of Organic Chemicals

Pyridine-4-carboxylic acid

see isonicotinic acid.

2,6-Pyridinedialdoxime

[2851-68-51 M 165.1, m 212O. Crystd from water.

Pyridine-2,5-dicarboxylic acid [ I 00-26-51 M 167.1, m 254O. Crystd from dilute HCl. Pyridine-2,6-dicarboxylic acid

see dipicolinic acid.

Pyridine-3,4-dicarboxylicacid [490-11-91 M 167.1, m256O. Crystd from dilute aqueous HCI. Pyridine hydrobromide perbromide (pyridinium bromide perbromide) /39416-48-31 M 319.9, m 130° (dec), 132-134O (dec). It is a very good brominating agent - liberating one mol. of Br2. Purified by recrystn from glacial acetic acid (33g from lOOml of AcOH). [Fieser and Feiser Reagents for Organic Chemistry Vol 1 967 1 9 6 7 . Pyridine hydrochloride [628-13-71 M 115.6, m 144O, b 218O. Crystd from CHC13/ethyl acetate and washed with ethyl ether. Pyridine N-oxide [694-59-71 M 95.1, m 67O. Purified by vacuum sublimation. Pyridine 3-sulphonic acid [636- 73-71 M 159.2, m 352-356O, 365-366O (dec), 356-357O, 357O. Purified by recrystn from H20 or aqueous EtOH as needles or plates. It has a basic pKa25 of 3.22 (in H20) and 2.89 (in 12% aqueous EtOH) [Evans and Brown JOC 27 3127 1962; IR: Arnett and Chawla JACS 100 214 19781. UV in 50% aqueous EtOH: hmax at 208 and 262nm. The ammonium salt has m 243O (from H20), the sulphonyl chloride has m 133-134O (from pet ether), the amide has m 110-11lo (from H20), the hydrochloride has m > 300° (dec), and the N-methyl betuine has m 130° (from H20). [Gastel and Wibaut Rec Trav Chim Pays Bas 53 1031 1934; McIlvain and Goese JACS 65 2233 1943; Machek M 72 7719381. Pyridoxal hydrochloride, pyridoxamine (vitamin B6) see entries in Chapter 5 .

hydrochloride and pyridoxine

hydrochloride

1-(2-PyridyIazo)-2-naphthol (PAN) [SS-SS-S] M 249.3, m 140-142O. Purified by repeated crystn from MeOH. It can also be purified by sublimation under vacuum. Purity can be checked by TLC using a mixed solvent (pet ether, ethyl ether, EtOH; 1O:lO:l) on a silica gel plate.

4-(2-Pyridylazo)resorcinol (PAR) [1141-59-91 M 215.2, m >19S0(dec), ,,A 415nm, E 2,59 x lo4 (pH 6-12). Purified as the sodium salt by recrystn from 1:l EtOWwater. Purity can be checked by TLC using a silica gel plate and a mixed solvent (n-BuOH:EtOH:2M NH3; 6:2:2). Pyridyldiphenyltriazine EtOWdimethylformamide.

[1046-56-61 M 310.4, m 191-192O. Purified by repeated recrystn from

R - ( + ) - [27854-88-21 and S-(-)- [42732-22-91 1-(4-pyridyI)ethanol M 123.2, m 63-65O6769O, [a]io+49.80 (c 0.5, EtOH). Purified by recrystn from pet ether. The (-)-di-0-benzoyl tartrate salr has m 146-148O (from EtOH). [UV, ORD: Harelli and Samori JCS Perkin Trans 2 1462 19741. The racemate recrystallises from Et2O m 74-76O, b 90-94O/lmrn [Ferles and Attia Coll Czech Chem Commun 38 61 1 1973; UV, NMR: Nielson et al. JOC 29 2898 19641. Pyrocatechol

see catechol.

Pyrogallol [87-66-11 M 126.1, m 136O. Crystd from EtOH/benzene L-Pyroglutamic acid [98-66-11M 129.1, m 162-164O, [ c ~ ] 2 5 0 4 ~-loo (c 5, HzO). Crystd from EtOH by addition of pet ether.

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