Previous Page 178
Purification of Organic Chemicals
3,6-Dichlorophthalic anhydride /4466-59-51 M 189-191°, 191-191S0, b 339O. Boil in xylene (allowing any vapours which would contain H20 to be removed, e.g. Dean and Stark trap), which causes the acid to dehydrate to the anhydride and cool. Recryst from xylene [Villiger B 42 3539 1909; Fedoorow Izv Akud SSSR Otd Chem 397 1948, Chem Abstr 1585 19481. 1,2-Dichloropropane [78-87-51 M 1 1 3 O , b 95.9-96.2O, d 1.158, n 1.439. Distd from CaH2. 2,2-Dichloropropane [594-20-71 M 113.0, b 69.3O, d 1.090, n 1.415. Na2C03 soln, then distilled water, dried over CaC12 and fractionally distd.
Washed with aqueous
1,3-Dichloro-2-propanonesee sym-dichloroacetone. 2,6-Dichloropurine [5451-40-I] M 189.0, m 180-181S0, 181°, 185-19S0(dec), 188-189O. It can be recrystd from 150 parts of boiling H20 and dried at 100° to constant weight. Soluble in EtOAc. The HgC12 salt separates from EtOH soln. U V : kmax 275nm (E 8.9K) at pH 1; and 280nm (E 8.5K) at pH 11 [Elion and Hitchings JACS 78 3508 1956; Schaeffer and Thomas JACS 80 3738 1958; Beaman and Robins J Appl Chem 12 432 1962; Montgomery JACS 78 1928 19561. 2,6-Dichloropyridine [2402-78-01 M 148.0, m 87-88O, 3,s-Dichloropyridine [2457-47-81 M 148.0, m 64-65O. Crystd from EtOH. 4,7-Dichloroquinoline [86-98-61 M 198.1, m 86.4-87.4O, b 148°/10mm. 95% EtOH.
Crystd from MeOH or
-
5,7-Dic hloro-8-quinolinol see 5,7 -dichloro-8 hy droxy q uinolin e. 2,3-Dichloroquinoxaline [2213-63-01 M 199.0, m 152-153O, 152-154O. Recrystd from C6H6 and dried in a vacuum [Cheeseman JCS 1804 19551. 2,6-Dichlorostyrene [28469-92-31 M 173.0, b 72-73O/2mm, d 1.4045, n 1.5798. Purified by fractional crystn from the melt and by distn. p-a-Dichlorotoluene see p-chlorobenzyl chloride. 2,4-Dichlorotoluene [95-73-81 M 161.1, m -13S0, b 61-62O/3mm, d 1.250, n 1.5513, 2,6-Dichlorotoluene [I 18-69-41 M 161.1, b 199-200°/760mm, d 1.254, n 1.548, [ 9 5 - 7 5 - 0 1 M 161.1, m -16O, b 20S0/760mm, d 1.2541, n 1.549. 3,4-Dichlorotoluene Recrystd from EtOH at low temperature or fractionally distd. a,a'-Dichloro-p-xylene [623-25-61 M 175.1, m
looo.
Crystd from benzene and dried under vacuum.
Dicinnamalacetone [622-21-91 M 314.4, m 146O. Crystd from benzene/isooctane (1 :1). Dicumyl peroxide [80-43-31 M 270.4, m 39-40O. Crystd from 95% EtOH (charcoal). Stored at Oo. Potentially EXPLOSIVE. 9,lO-Dicyanoanthracene [I217-45-41 M 228.2. Recrystd twice from pyridine [Mattes and Farid JACS 108 7356 19861. 1,2-Dicyanobenzene [91-15-61 M 128.1, m 141O. Recrystd from hot toluene. 1,4-Dicyanobenzene [623-26-71 M 128.1, m 222O. Crystd from EtOH. Dicyanodiamide see cyanoguanidine.
179
Purification of Organic Chemicals
1,4-Dicyanonaphthalene [3029-30-91 M 178.2, m 206O. Purified by crystn and sublimed in vucuo. 1,3-Dicyclohexyl carbodimide [538-7 5 - 0 1 M 206.3, m 34-3S0, b 95-97O/0.2mm, 120121°/0.6mm, 155"/11mm. It is sampled as a liquid after melting in warm H20. It is sensitive to air and it is a potent skin im-tant. It can be distd in a vacuum and stored in a tightly stoppered flask in a freezer. It is very soluble in CH2C12 and pyndine where the reaction product with H20, after condensation, is dicyclohexyl urea which is insoluble and can be removed by filtration. Alternatively dissolve in CH2C12 add powdered anhyd MgS04 shake 4h, filter, evaporate and distil at 0.6 mm press and oil bath temperature 145O. [Biochern Prep 10, 122 1963; A 571 83 1951; A 612 11 19581. Dicyclohexyl-18-crown-6 [16069-36-61 M 372.5. Purified by chromatography on neutral alumina and eluting with an etherhexane mixture [see lnorg Chern 14 3132 19751. Dissolved in ether at ca 40°, and spectroscopic grade MeCN was added to the soln which was then chilled. The crown ether ppted and was filtered off. It was dried in vucuo at room temperature [Wallace JPC 89 1357 1983. Di-n-decylamine [I 120-49-61 M 297.6, m 34O. b 153O/lmm, 359O/760mm. Dissolved in benzene and ppted as its bisulphate by shaking with 4M H2SO4. Filtered, washed with benzene, separating by centrifugation, then the free base was liberated by treating with aqueous NaOH [McDowell and Allen JPC 65 1358 19611. Didodecylamine [3007-31-61 M 353.7, m 51.8O. Crystd from EtOWbenzene under N2. Didodecyldimethylammonium bromide [3282- 73-31 M 463.6. Recrystd from acetone, acetone/ether mixture, then from ethyl acetate, washed with ether and dried in a vacuum oven at 60° [Chen et al. J P C 88 1631 1984; Rupert et al. JACS 107 2628 1985; Halpern et al. JACS 108 3920 1986; Allen et al. JPC 91 2320 19871.
Dienestrol [4,4'-(diethylidene-ethlene)diphenol, Dienol] [84-17-37] M 266.3, m 227-228O, 231-233O. Crystd from EtOH or dilute EtOH, sublimes at 130°/lmm. The diucerute has m 119-120° (from EtOH) [Hobday and Short JCS 609 19431. Diethanolamine [I 11-42-21 M 105.1, m 28O, b 154-155°/10mm, 270°/760mm. distd twice, then fractionally crystd from its melt.
Fractionally
3,4-Diethoxy-3-cyclobutene-1,2-dione (diethyl squarate) [ 5 3 2 1 - 8 7 - 8 1 M 170.2, b 8991°/0.4mm, 88-92°/0.4mm, di0 1.162, n y 1.5000. Dissolve in Et20, wash with Na2C03, H20 and dry (Na2S04), filter, evaporate and distil using a Kugelrohr or purify by chromatography . Use a Keiselgel column and elute with 20% EtzO-Pet ether (b 40-60°) then with Et20-pet ether (1: l), evaporate and distil in vucuo. [Dehmlow and Schell B 113 1 1980; Peni and Moore JACS 112 1897 1990; IR: Cohen and Cohen JACS 88 1533 19661. It can cause severe dermatitis [Foland et al. J A C S 111 975 19891. 1,2-Diethoxyethane see ethylene glycol diethyl ether. N,N-Diethylacetamide [ 2 2 3 5 - 4 6 - 3 1 M 157.2, b 86-88O, n 1.474, d 0.994. Dissolved in cyclohexane, shaken with anhydrous BaO and then filtered. The procedure was repeated three times, and the cyclohexane was distd off at 1 atmosphere pressure. The crude amide was also fractionally distd three times from anhydrous BaO. Diethyl acetamidomalonate [1068-90-21 M 217.2, m 96O. Crystd from benzene/pet ether. Diethyl acetylenedicarboxylate [ 7 6 2 - 2 1 - 0 1 M 170.2, b 60-62°/0.3mm, 107-110°/1 l m m , 118-120°/20mm, d i O 1.0735, n',O 1.4428. Dissolve in C6H6, wash with NaHC03, H20, dry over Na2S04, filter, evaporate and distil in a vacuum [IR: Walton and Hughes JACS 79 3985 1957; Truce and Kruse JACS 81 5372 19591.
180
Purification of Organic Chemicals
Diethylamine [109-89-71 M 73.1, b 55S0, d 0.707, n 1.38637. Dried with LiAlH4 or KOH pellets. Refluxed with, and distd from, BaO or KOH. Converted to the p-toluenesulphonamide and crystd to constant melting point from dry pet ether (b 90-120°), then hydrolysed with HCl, excess NaOH was added, and the amine passed through a tower of activated alumina, redistd and dried with activated alumina before use [Swift JACS 64 115 19421. Diethylamine hydrochloride [660-68-41 M 109.6, m 223.5O. Crystd from absolute EtOH. Also crystd from dichloroethaneA4eOH. Hygroscopic.
trans-4-(Diethylamino)azobenzene [3588-91-81 M 320.5, m 171O. chromatography [Flamigni and Monti JPC 89 3702 198.51.
Purified by column
N,N-Diethylaniline [91-66-71 M 149.2, b 216S0, d 0.938, n 1.5409. Refluxed for 4h with half its weight of acetic anhydride, then fractionally distd under reduced pressure (b 92O/IOmm). Diethyl azodicarboxylate (DEAD) {1972-28-71 M 174.2, b 104S0/12mm, 211-213O/atm, d i 0 1.110, n v 1.420. Dissolve in toluene, wash with 10% NaHCO3 till neutral (may require several washes if too much hydrolysis had occurred (check IR for OH bands), then wash with H20 (2 x), dry over Na2S04, filter, evaporate the toluene and distil through a short Vigreux column. Main portion boils at 107-111°/15mm [Org Synth Coll Vol 111376 19.551. 5,s-Diethylbarbituric acid [57-44-31 M 184.2, m 188-192O. Crystd from water or EtOH. Dried in a vacuum over P2O5. Diethyl bromomalonate [685-87-01 M 239.1, b 116-118°/10mm, 122-123°/20mm, d i 0 1.420, nLo 1.4507. Purified by fractional distn in a vacuum. IR: 1800 and 1700cm-' [Abramovitch Canad J Chem 37 1146 1959; Bretschneider and Karpitschka M 84 1091 10531. Diethyl tert-butylmalonate [759-24-01 M 216.3, b 40-42O/0.03, 102-104°/11mm, 109.51 10S0/17mm, 205-210°/760mm, d i O0.980, n i o 1.425. Dissolve in Et20, wash with aqueous NaHC03, H20, dry (MgS04), filter, evaporate and distil residue. Identified by hydrolysis to the acid and determining the neutralisation equiv (theor: 80.0). The acid has m 155-157O efferv [Hauser, Abramovitch and Adams JACS 64 2715 1942; Bush and Beauchamp JACS 75 2949 19531. N,N'-Diethylcarbanilide [611-92-71 M 240.3, m 79O. Crystd from EtOH. Diethyl carbitol see Diethylene glycol diethyl ether. Diethyl carbonate [ZO5-58-8] M 118.1, b 126.8O, d 0.975, n25 1.38287. It was washed (100ml) with an aqueous 10% Na2C03 (2Oml) solution, saturated CaC12 (2Oml), then water (3Oml). After drying by standing over solid CaC12 for 1h (note that prolonged contact should be avoided because slow combination with CaC12 occurs), it should be fractionally distd.
l,l'-Diethyl-2,2'-cyanine iodide in a vacuum oven at 80° for 4h.
[977-96-81 M 454.4, m 274O(dec). Crystd from EtOH and dried
N,N-Diethylcyclohexylamine [91-65-61 M 155.3, b 193°/760mm, d 0.850, n 1.4562. Dried with BaO and fractionally distd.
sym-Diethyldiphenylurea see N,N-diethylcarbanilide. Diethylene glycol [ I l l - 4 6 - 6 1 M 106.1, f.p. -lOSO, b 244.3O, d 1.118, d 51.4490, n 1.4475. Fractionally distd under reduced pressure (b 133O/14mm),then fractionally crystd by partial freezing.
Purification of Organic Chemicals
181
Diethylene glycol diethyl ether [ I 1 2 - 3 6 - 7 1 M 162.2, b 85-86°/10mm, 188.2188.3°/751mm, d 0.909. Dried with MgS04, then CaH2 or LiAIH4, under N2. If sodium is used the ether should be redistd alone to remove any products which may be formed by the action of sodium on the ether. As a preliminary purification, the crude ether (2L) can be refluxed for 12h with 25ml of conc HC1 in 2OOml of water, under reduced pressure, with slow passage of N2 to remove aldehydes and other volatile substances. After cooling, addn of sufficient solid KOH pellets (slowly and with shaking until no more dissolve) gives two liquid phases. The upper of these is decanted, dried with fresh KOH pellets, decanted, then refluxed over, and distd from, sodium. Diethylene glycol dimethyl ether see diglyme. Diethylene glycol ditosylate 17460-82-41 M 414.5, m 86-87O, 87-8S0, 88-89O. Purified by recrystn from Me2CO and dried in a vacuum. Diethylene glycol mono-n-butyl ether [I 12-34-51 M 162.2, b 69-70°/0.3mm, 230S0/760, d 0.967, n 1.4286. Dried with anhydrous K2CO3 or CaS04, filtered and fractionally distd. Peroxides can be removed by refluxing with stannous chloride or a mixture of FeSO4 and KHS04 (or, less completely, by filtration under slight pressure through a column of activated alumina). Diethylene glycol monoethyl ether [ 1 1 1 - 9 0 - 0 ] M 134.2, b 201.9O, d 0.999, n 1.4273, n25 1.4254. Ethylene glycol can be removed by extracting 250g in 750ml of benzene with 5ml portions of water, allowing for phase separation, until successive aqueous portions show the same volume increase. Dried, and freed from peroxides, as described for diethylene glycol mono-n-butyl ether. Diethylene glycol monomethyl ether [ I l l - 7 7 - 3 1 M 120.2, b 194O, d 1.010, n 1.423. Purified as for diethylene glycol mono-n-butyl ether. Diethylenetriamine see 2,2'-diaminodiethylamine.
Diethylenetriaminepenta-acetic acid [67-43-61 M 393.4, m 219-220°. Crystd from water. Dried under vacuum or at 1 loo. [Bielski and Thomas JACS 109 7761 1987. Diethyl ether see ethyl ether. Diethyl ethoxymethylene malonate [87- 13-81 M 216.2, b 014°/0.2mm, 109°/0.5mm, 279283O/atm, d i O1.079, n v 1.4623. Likely impurity is diethyl diethoxymethylene malonate which is difficult to separate from diethyl ethoxymethylene malonate by distn and it is necessary to follow the course of the aistn by the change in refractive index instead of boiling point. After a low boiling fraction is collected, there is obtained an intermediate fraction 1.414-1.4580) the size of which depends on the amount of diethoxymethylene compound. This fraction is fractionated through a 5-inch Vigreux column at low pressure avoiding interruption in heating. Fraction b 108-1 10°/0.25mm was ca loo lower than the submitters' (b 97.2O/0.25mm (n;' 1.4612-1.4623) [Org Synfh Coll Vol I11 395 1955; Fuson et al. JOC 11 197 1946; Duff and Kendal JCS 893 19481.
(4'
N , N ' - D i e t h y l f o r m a m i d e [ 6 1 7 - 8 4 - 5 ] M 101.2, b 29°/0.5mm, 61-63°/10mm, 176179°/758mm, 178.3-178.5°/760mm d i O0.906, n i 5 1.4313. Distd under reduced pressure then at atmospheric pressure [Wintcler et al. HCA 37 2370 1954; NMR: Hoffmann Z a n a f Chem 170 177 19591. Diethyl fumarate 1623-91-61 M 172.2, b 218O, d 1.052, n 1.441. Washed with aqueous 5% Na2C03, then with saturated CaC12 soln, dried with CaC12 and distd.
Di-(2-ethylhexyl)phthalate ('di-iso-octyl' phthalate) [ I 1 7 - 8 1 - 7 1 M 390.6, b 384O, 2 5 6 257O/lmm, d 0.9803, n 1.4863. Washed with Na2C03 soln, then shaken with water. After the resulting emulsion had been broken by adding ether, the ethereal s o h was washed twice with water, dried
182
Purification of Organic Chemicals
(CaC12), and evaporated. The residual liquid was distd several times under reduced pressure, then stored in a vacuum desiccator over P2O5 [French and Singer JCS 1424 19561
Diethyl ketone (3-pentanone) [96-22-01 M 86.1, b 102.1°, d 0.8099, n 1.392. Dried with anhydrous CaS04 or CuSO4, and distd from P2O5 under N2 or under reduced pressure. Further purification by conversion to the semicarbazone (recrystd to constant m 139O, from EtOH) which, after drying under vacuun over CaC12 and paraffin wax, was refluxed for 30min with excess oxalic acid, then steam distd and salted out with K2CO3. Dried with Na2S04and distd [Cowan, Jeffrey and Vogel JCS 171 19401. Diethyl phenyl orthoformate (diethoxy phenoxy ethane) [ 1 4 4 4 4 - 77-01 M 196.3, b 11 1°/llmm, 122°/13mm, d i 0 1.0099, nko 1.4799. Fractionated through an efficient column under vacuum [Smith Acta Chem Scand 10 1006 19561. Diethyl phthalate [84-66-21 M 222.2. b 172O/12mm, b 29S0/760mm, d25 1.1160, n 1.5022. Washed with aqueous Na2C03, then distilled water, dried (CaC12), and distd under reduced pressure. Stored in a vacuum desiccator over P2O5. Diethyl phthalimido malonate [56680-61-51 M 305.3, m 72-74O, 73-74O. Dissolve in xylene and when the temperature is 30° add pet ether (b 40-60°)and cool to 200 whereby the malonate separates as a pale brown powder [Booth et al. JCS 666 19441. Alternatively, dissolve in C6H6, dry over CaC12, filter, evaporate and the residual oil solidifies. This is ground with EtzO, filter and wash with Et20 until white in colour, and dry in a vacuum. It has a pKa of 9.17 (H20) and the anion has hmax 254nm ( E 18.5K) [Clark and Murray OrgSynrh Coll Vol I 271 1941; UV of Na salt: Nnadi and Wang JACS 92 4421 19701.
2,2-Diethyl-1,3-propanediol[I 15-76-41M 132.2, m 61.4-61.8O. Crystd from pet ether (b 65-70O). Diethyl pyrocarbonate (DEP) [I609-47-8] M 162.1, b 38-40°/12mm, 160-163O/atm, d i O 1.119, nLo 1.398. Dissolve in Et20, wash with dilute HCI, H20, dry over Na2S04, filter, evaporate and distil the residue first in vacuo then at atmospheric pressure. It is soluble in alcohols, esters, ketones and hydrocarbon solvents. A 50% w/w soln is usually prepared for general use. Treat with great CAUTION as DEP irritates the eyes, mucous membranes and skin. [Boehm and Mehta B 71 1797 1938; Thoma and Rinke A 624 30 19591. Diethylstilboesterol [56-25-11 M 268.4, m 169-172O. Crystd from benzene. Diethyl succinate [123-25-11 M 174.2, b 105°/15mm, d 1.047, n 1.4199. Dried with MgS04, and distd at 15mm pressure. Diethyl sulphate [64-67-51 M 154.2, b 96°/15mm, 118°/40mm, d 1.177, n 1.399. Washed with aqueous 3% Na2C03 (to remove acidic material), then distilled water, dried (CaC12), filtered and distd. Causes blisters to the skin. Diethyl disulphide [110-81-6] M 122.3, b 154-15S0, d 0.993, n 1.506. Dried with silica gel or MgS04 and distd under reduced pressure (optionally from CaC12). Diethyl sulphide [352-93-21 M 90.2, m 0°/15mm, 90.1°/760mm, d 0.837, n 1.443. Washed with aq 5% NaOH, then water, dried with CaC12 and distd from sodium. Can also be dried with MgS04 or silica gel. Alternative purification is via the Hg(I1) chloride complex [(Et)2S.2HgC12] (see dimethyl sulphide). Diethyl (-)-D- (from the non-natural) [13811-71-71 and (+)-L- (from the natural acid) [89-9121 tartrate M 206.2, m 17O, 80°/0.5mm, 150°/11mm, 162°/19mm, 278-282O/atm, df4O 1.204, nLo 1.4476, [alL0*26.So (c 1, H2O) and +8S0 (neat), [a]*&f30° (c 1, H 2 0 ) . Distd under high vacuum and stored under vacuum or in an inert atm in a desiccator in round bottomed flasks equiped with a vac stopcock. Have also been dist by Kugelrohr distn and by wiped-film molecular distn. Slightly sol in H20 but miscible in EtOH and Et20. [Gao et al. JACS 109 5770 1987; IR: Pristera AC 25 844 19531.
183
Purification of Organic Chemicals
Diethyl terephthalate [ 6 3 6 - 0 9 - 0 1 M 222.2, m 44O, 142O/2mrn, 302°/760mm. toluene and distd under reduced pressure.
Crystd from
sym-Diethylthiourea [105-55-5] M 132.2, m 76-77O. Crystd from benzene. Difluoroacetic acid [496-16-21 M 96.0, m -0.35O, b 67-70°/20mm, 134O/760mm, d i 0 1S 3 0 , nio 1.3428. Purified by distilling over P2O5. The acid chloride is a fuming liquid b 25O, and the amide has b 108.6O/35mm, m 5 2 O (from C6H6) [Henne and Pelley JACS 74 1426 1952, Coffman et al. JOC 14 749 1949; NMR: Meyer et al. JACS 75 4567 19531. It has a Ka value of 5.72 x [Wegscheider ZPC 69 614 19091.
4,4'-Difluoro-3,3'-dinitrophenylsulphone see Bis-(4-fluoro-3-nitrophenyl)sulphone. Digitonin [11024-24-11 M 1229.3, m >270°(dec), [a]:!6- 6 3 O (c 3, MeOH). Crystd from aqueous 85% EtOH or MeOWethyl ether. Digitoxigenin [142-62-41 M 374.5, m 253O, [a]:!6+21° (c 1, MeOH). Crystd from aqueous 40% EtOH. D(+)-Digitoxose [527-52-61 M 148.2, m 112O, ether, or ethyl acetate.
+57O (c 1, H20). Crystd from MeOWethyl
Diglycolic acid [IIU-99-61 M 134.1, m 148O (monohydrate). Crystd from water. Diglycyl glycine [556-33-21 M 189.2, m 246O(dec). Crystd from H20 or H20/EtOH and dried at 1100. Diglyme [ I l l - 4 6 - 6 1 M 134.2, b 62O/17mrn, 7S0/35mm, 160°/760mm, d 0.917, n 1.4087. Dried with NaOH pellets or CaH2, then refluxed with, and distd (under reduced pressure) from Na, CaH2, LiAlH4, NaBH4 or NaH. These operations were carried out under N2. The amine-like odour of diglyme has been removed by shaking with a weakly acidic ion-exchange resin (Amberlite IR-120) before drying and distn. Addn of 0.01% NaBH4 to the distillate inhibits peroxidation. Purification as for dioxane. Also passed through a 12-in column of molecular sieves to remove water and peroxides. Digoxin [ 2 0 8 3 0 - 7 5 - 5 1 M 781.0, m 265O(dec), aqueous EtOH or aqueous pyridine.
+14.0° (c 10, pyridine).
Crystd from
4,4'-Di-n-heptyloxyazoxybenzene [2635-26-91M 426.6, m 75O, 95O (smectic + nematic) and 127O (nematic + liquid). Purified by chromatography on A1203 (benzene), recrystd from hexane or 95% EtOH and dried by heating under vacuum. The liquid crystals can be sublimed in vucuo. [Mellifiori et al. Spectrochim Actu A 37(A) 605 1981; Dewar and Schroeder JACS 86 5235 1964; Weygand and Glaber J prakt Chemie 155 332 19401. 9,lO-Dihydroanthracene [613-31-01 M 180.3, m 110-110.5°. Crystd from EtOH [Rabideau et al. JACS 108 8 130 I9861. 2,3-Dihydrobenzofuran (coumaran) [ 4 9 6 - 1 6 - 2 1 M 120.2, m -21S0, 72-73O/12mm, 7881°/15mm. 84O/17rnm, 1 8 8 O /atm, d i 0 1.065, n t o 1.5524. Suspend in aqueous NaOH and steam distil. Saturate the distillate with NaCl and extract with Et20, dry extract (MgS04), filter, evap and distil the residue. It gives a strong violet colour with FeC13 + H2S04and forms a yellow picrate, m 76O, from EtOH or C6H6 which loses coumaran in a desiccator [Bennett and Hafez JCS 287 1941; Baddeley et al. JCS 2455 19561. Dihydrochloranil [1198-5-6] M 247.9. Crystd from EtOH [Rabideau et al. JACS 108 8130 19861. Dihydrocholesterol see cholestanol.
184
Purification of Organic Chemicals
Dihydrocinnamic acid [501-52-0]M 150.2, m 48-49O. Crystd from pet ether (b 60-80O).
3,4-Dihydro-3,4-dioxo-l-naphthlenesulphonic acid sodium salt (1,2-naphthoquinone-4sulphonic acid sodium salt) [521-24-41M 260.2. Yellow crystals from aqueous EtOH and dry at 80" in vucuo. Solubility in H20 is 5% [Org Synth Coll Vol I11 633 1955;Danielson JBC 101 507 1933;UV: Rosenblatt et al. A C 27 1290 19551. 1,4-Dihydro-1,4-epoxynaphthalene [573-57-91M 144.2, m 53-54.S0, 53-56O, 55-56O. Dissolve in EtzO, wash with H20, dry over K2CO3, filter, evaporate and dry the residue at 15mm, then recrystallise from pet ether (b 40-60°), dry at 25°/0.005mm and sublime (sublimes slowly at room temp)[Wittig and Pohmer B 89 1334 1956;Gilman and Gorsich JACS 79 2625 1957. D i h y d r o p y r a n (3,4-dihydro-2H-pyran) if lo-87-21 M 84.1, b 84.4°/742mm, 85.485.6°/760mm, d i 0 0.9261, n i o 1.4423. Partially dried with Na2C03, then fractionally distd. The fraction b 84-85O, was refluxed with Na until hydrogen was no longer evolved when fresh Na was added. It was then dried, and distd again through a 60 x 1.2cm column packed with glass rings [Brandon et al. JACS 72 2120 1950;UV: Elington at al. JCS 2873 1952,NMR: Bushweller and O'Neil TET LETT4713 19691. It has been characterised as the 2,3,5-dinitrobenzoylo~-tetruhydrofurun derivative, m 103O which forms pale yellow crystals from dihydropyran-Et20 [Woods and Kramer JACS 69 2246 1947.
3,4-Dihydro-2H-pyrido[l,2a]-pyrimidin-2-one [5439-14-51M 148.2, m 185-187O, 187-18S0, 191-191.5O. Dissolve in CHC13, filter, evaporate then recrystallise the residue from EtOH-Me2CO (needles) which can be washed with Et20 and dried. It can also be recrystd from CHCl3-pet ether or CHClrhexane. The hydrochloride has m 295-295O (dec, from EtOH or MeOH-Et20), the hydrobromide has m 299-3m0(dec, from MeOH-Et2O) and the picrute has m 224-226O(corr), m 219-220° from EtOH. [Adams and Pachter JACS 74 4906 1952;Lappin J O C 23 1358 1958;Hurd and Hayao JACS 77 115 19551. Dihydrotachysterol [67-96-91M 398.7, m 125-127O, [a]? +97O (CHCI3). MeOH.
Crystd from 90%
1,2-Dihydroxyanthraquinone see alizarin. 1,4-Dihydroxyanthraquinone see quinizarin.
1,s-Dihydroxyanthraquinone see anthrarufin. 1,s-Dihydroxyanthraquinone [I 17-10-21M 240.1, m 193-197O. Crystd from EtOH and sublimed in a vacuum.
2,4-Dihydroxyazobenzene [2051-85-61M 214.2, m 228O. Crystd from hot EtOH (charcoal). 2,3-Dihydroxybenzaldehyde [24677-78-91M 138.1, m 135-136O, 2,4-Dihydroxybenzoic acid [95-01-21 M 154.1, m 226-227O(dec). Crystd from water. 2,5-Dihydroxybenzoic acid [490-79-91 M 154.1, m >200°(dec). Dried in a vacuum desiccator over silica gel.
Crystd from benzenelacetone.
2,6-Dihydroxybenzoic acid [303-07-11M 154.1, m 167O(dec). Dissolved in aqueous NaHC03 and the s o h was washed with ether to remove non-acidic material. The acid was ppted by adding H2S04, and recrystd from water. Dried under vacuum and stored in the dark [Lowe and Smith JCSFT I 69 1934 19731. 2,4-Dihydroxybenzophenone [131-56-61M 214.2, m 145.5-147O. Recrystd from MeOH.
2,s-Dihydroxybenzyl alcohol [495-08-91M 140.1, m looo. Crystd from CHC13. Sublimed.
185
Purification of Organic Chemicals
2,2'-Dihydroxybiphenyl [I 806-29-71 M 186.2, m 108.5-109.5°. then sublimed at 600/104mm.
Repeatedly crystd from toluene,
3a,7a-Dihydroxycholanic acid [474-25-91 M 239.6, m 143O, [a]:!6 from ethyl acetate.
+14O (c 2, EtOH). Crystd
6,7-Dihydroxycoumarin (esculetin) [305-01 -I] M 178.2, m 268-270°(dec). Crystd from glacial acetic acid. See also esculetin. 7,8-Dihydroxycoumarin [486-35-I ] M 178.2, m 256O(dec). Crystd from aqueous EtOH. Sublimed.
3,4-Dihydroxy-3-cyclobutene-1,2-dionesee squaric acid. 2,2'-Dihydroxy-6,6'-dinaphthyl disulphide [6088-51-31 M 350.5, m 220-223O. Recryst from hot glacial acetic acid. [Barnett and Seligman Science 116 323 19521. trans-2,3-Dihydroxy-1,4-dioxane [4845-50-51 M 120.1, m 91-95O, looo. Recryst from Me2CO. With phenylhydrazine it gives glyoxal phenylhydruzone m 175O (from Me2CO-pet ether). The diacetyl derivative has m 105-106° [Head JCS 1036 1955, Raudnitz Chemistry & Industry (London) 166 19561.
2,5-Dihydroxy-1,4-dithiane [40018-26-61 M 152.2, m (142-147O ?) 150-152O, 151O. Recrystd from EtOH. The 2,5-diethoxy-dithiane has m 91° (92-93O) crystallises from pet ether and can be sublimed at 60°/0.001mm [Hormatka and Haber M 85 1088 1954; Thiel et al. A 611 121 1958; Hesse and Jckder B 85 924 19521. (N,N-Dihydroxyethy1)glycine [150-25-41 M 163.2, m 193O(dec). Dissolved in a small volume of hot water and ppted with EtOH, twice. Repeated once more but with charcoal treatment of the aqueous soh, and filtered before addition of EtOH. 2,4-Dihydroxyimidazole see hydantoin. 3,4-Dihydroxyisoflavone [578-86-91 M 256.3, m 234-236O. Crystd from aqueous 50% EtOH.
2,6-Dihydroxyisonicotinic acid
see
citrazinic acid.
Dihydroxymaleic acid (dihydroxyfumaric acid hydrate) Crystd from water.
[133-38-01 M 148.1, m 155O(dec).
5,7-Dihydroxy-4'-methoxyflavone[491-80-51 M 284.3, m 261O. Crystd from 95% EtOH. 1,8-Dihydroxy-3-methylanthraquinone(chrysophanic acid) [ 4 8 1 - 7 4 - 3 1 M 245.3, m 196O. Crystd from EtOH or benzene and sublimed in a vacuum.
1,5-Dihydroxynaphthalene [83-56-71 M 160.2, m 165O(dec). Crystd from nitromethane.
1,6-Dihydroxynaphthalene [ 5 7 5 - 4 4 - 0 1 M 160.2, m 138-139O (with previous softening). Crystd from benzene/EtOH after treatment with charcoal. 5,8-Dihydroxy-1,4-naphthoquinone see naphthazarin. 2,5-Dihydroxyphenylacetic acid (homogentisic acid) from EtOWCHC13.
[ 4 5 1 -13-81 M 168.2, m 152O. Crystd
-
S-P-(3,4-Dihydroxyphenyl)alanine(DOPA) [59-92-71 M 197.2, m 285S0(dec), [a];' 12.0° (1M HCl). Likely impurities are vanillin, hippuric acid, 3-methoxytyrosine and 3-aminotyrosine. Crystd by
186
Purification of Organic Chemicals
dissolving in dilute HCl and adding dilute ammonia to give pH 5, under N2. Alternatively, crystd from aqueous EtOH. Unstable in aqueous alkali.
2,3-Dihydroxytoluene [452-86-81 M 124.1, m 65-66O. Crystd from C6H6. Purity checked by TLC.
-
1,3-Diiminoisoindoline [3468-11-91 M 145.2, m 193-194O (dec), 196O (dec), 197O (dec). It crystallises from H20, MeOH or MeOH-Et2O (charcoal) in colourless prisms that become green on heating. [Elvidge and Linstead JCS 5000 19521. It has pKa 8.27, IR (nujol): 3150 and 690 cm-', and UV: hmax 251nm (E 12.5K), 256nm (E 12.5K) and 303nm (E 4.6K) [Elvidge and Golden JCS 700 1957; Clark et al. JCS 3593 19531. The thiocyanate has m 250-255O (dec), the monohydrochloride has m 300-301° (turns green) and the dihydrochloride has m 326-328O (turns green) and the picrute cryst from EtHO has m 299O (dec). p-Diiodobenzene 1624-38-41 M 329.9, m 132-133O. Crystd from EtOH or boiling MeOH, then air dried. 172-Diiodoethane [624-73-71 M 281.9, m 81-8407d 2.134. Dissolved in ether, washed with satd aq Na2S203, drying it over MgS04 and evaporating the ether in vucuo [Molander et al. JACS 109 453 19871.
5,7-Diiodo-8-hydroxyquinoline[83-73-81 M 397.0, m 214-21S0(dec). Crystd from xylene and dried at 70° in a vacuum. Diiodomethane [75-11-61 M 267.8, m 6.1°, b 66-70°/11-12mm, d 3.325. Fractionally distd under reduced pressure, then fractionally crystd by partial freezing, and stabilized with silver wool if necessary. It has also been purified by drying over CaC12 and fractionally distd from Cu powder. 5,7-Diiodo-8-quinolinol
see 5,7-diiodo-8-hydroxyquinoline.
S-3,s-Diiodotyrosine (iodogorgoic acid) [300-39-01 M 469.0, m 204O(dec), [a]D +1S0 (in 1M HCI). Likely impurities are tyrosine, 3-iodotyrosine and iodide ions. Crystd from cold dilute ammonia by adding acetic acid to give pH 6. It can also be crystd from aq 70% EtOH. Diisopropanolamine ether.
[110-97-41 M 133.2, m 41-4407d 1.004. Repeatedly crystd from dry ethyl
(-)-2,3:4,6-Di-0-isopropylidene-2-keto-L-gulonic acid monohydrate (- DAG) [18467- 77-11 M 292.3, m 1OO-10lo, 103O, [a]:' -21.6O (c 2.3, MeOH). Dissolve in Et20, filter, dry (MgS04), filter, evaporate to give a yellow oil. Addition of one drop of H20 induces crystn to the monohydrate, which also forms rhombic crystals by recrystn from 95% EtOH-H20 at room tempereture. [Flatt et al. S 815 1979; Reichstein and Grussner HCA 17 3 11 1934; Takagi and Jeffrey Actu Cryst Sect B 34 2932 1978; cf Org Synth 55 80 19761.
[a]i5
1,2:5,6-Di-O-isopropylidene-D-mannitol [1707-77-31 M 262.3, m 121-12S0, 122O, +1.2O (c 3, H20). Although quite soluble in H20 it gives a purer product from this solvent, forming needles [Baer JACS 67 338 1945; NMR: Curtis et al. JCS Perkin Trans I 1756 19771. Diisopropylamine [108-18-91 M 101.2, b 83S0/760mm, n 1.39236, d 0.720. NaOH, or refluxed over Na wire or NaH for three minutes and distd into a dry receiver under N2.
Distd from
Diisopropyl ether see isopropyl ether. Diisopropylethylamine [7087-68-51 M 129.3, b 127O. Distd from ninhydrin, then from KOH [Dryland and Sheppard, JCSFT 1 125 19861. Diisopropyl ketone (565-80-0] M 114.2, b 123-12S0, d 0.801, n 1.400. Dried with CaS04, shaken with chromatographic alumina and fractionally distd.
187
Purification of Organic Chemicals
D i k e t e n e [ 6 7 4 - 8 2 - 8 1 M 84.1, m -7O, b 66-68°/90mm, d 1.440, n 1.4376, n25 1 . 4 3 4 8 . Diketene polymerizes violently in the presence of alkali. Distd at reduced pressure, then fractionally crystd by partial freezing (using as a cooling bath a 1:l s o h of Na2S203 in water, cooled with Dry-ice until slushy, and stored in a Dewar flask). Freezing proceeds slowly, and takes about a day for half completion. The crystals are separated and stored in a refrigerator under N2.
E ~ ~ F ~
2,2'-Diketospirilloxanthin [ 2 4 0 0 9 - 1 7 - 4 1 M 624.9, m 225-227O, 550(349nm), Purified by 820(422nm), 2125(488nm), 2725(516nm), 2130(551nm) in hexane. chromatography on a column of partially deactivated alumina. Crystd from acetone/pet ether. Stored in the dark, in an inert atmosphere at Oo. Dilauroyl peroxide [105-74-81 M 398.6, m 53-55O. EXPLOSIVE.
Crystd from n-hexane.
Potentially
Dilituric acid see 5-N-nitrobarbituric acid. Dimedone [126-81-81 M 140.2, m 148-149O. Crystd from acetone (ca 8ml/g), water or aqueous EtOH. Dried in air. 1,2-Dimercapto-3-propanol [59-52-91 M 124.2, b 82-84°/0.8mm, d 1.239, n 1.5732, 1,3-Dimercapto-2-propanol[584-04-31 M 124.2, b 82°/1.5mm. Ppted as the mercury mercaptide (see Bjoberg B 75 13 19421, regenerated with HzS, and distd at 2.7mm [Rosenblatt and Jean AC 951 19551.
m e s o -2,3-Dimercaptosuccinic acid [304-55-21 M 182.2, m 191-192O (dec), 210° (dec), 210-211O (dec). Purified by dissolving in NaOH and precipitating with dilute HCI, dry and recrystallise from MeOH. It has pKa values of 3.0 and 3.9, and the IR has v at 2544 (SH) and 1689 (C02H) cm-'. The bis-S-ace@ deriv has m 183-185O (from EtOAc or Me2CO) and its Me ester has m 119-120° (from pet ether) [Gerecke et al. HCA 44 957 1961; Owen and Sultanbawa JCS 31 12 19491.
4,4'-Dimethoxyazobenzene [2396-60-31 M 242.3, m 162.7-164.7O. Chromatographed on basic alumina, eluted with benzene. Crystd from 2:2: 1 (v/v) methanoVethanoUbenzene. 4,4'-Dimethoxyazoxybenzene [1562-94-31 M 258.3, m 165O. Crystd from hot 95% EtOH, dried, then sublimed in a vacuum onto a cold finger. 3,4-Dimethoxybenzaldehyde
see veratraldehyde.
o-Dimethoxybenzene (veratrole) [91-16-71 M 137.2, m 23O, b 208.5-208.7, d 1.085, n25 1.53232. Steam distd. Fractionally distd from BaO, CaH2 or Na. Crystd from benzene or low-boiling pet ether at Oo. Fractionally crystd from its melt. Stored over anhydrous Na2S04. m-Dimethoxybenzene [151-10-01 M 137.2, b 212-213O, d 1.056, n 1.5215. aqueous NaOH, and water, then dried. Fractionally distd from BaO or Na.
Extracted with
p-Dimethoxybenzene [150-78-71 M 137.2, m 57.2-57.8O. Steam distd. Crystd from benzene, MeOH or EtOH. Dried under vacuum. Also sublimes under vacuum. 2,4-Dimethoxybenzoic acid [91-52-11 M 182.2, m 109O, 2,6-Dimethoxybenzoic acid [1466-76-81 M 182.2, m 186-187O. Crystd from water. 3,4-Dimethoxybenzoic acid [93-07-21 M 182.2, m 181-182O. Crystd from water or aq acetic acid. 3,5-Dimethoxybenzoic acid [1132-21-41 M 182.2, m 185-186O. Crystd from water, EtOH or aq acetic acid.
187
Purification of Organic Chemicals
D i k e t e n e [ 6 7 4 - 8 2 - 8 1 M 84.1, m -7O, b 66-68°/90mm, d 1.440, n 1.4376, n25 1 . 4 3 4 8 . Diketene polymerizes violently in the presence of alkali. Distd at reduced pressure, then fractionally crystd by partial freezing (using as a cooling bath a 1:l s o h of Na2S203 in water, cooled with Dry-ice until slushy, and stored in a Dewar flask). Freezing proceeds slowly, and takes about a day for half completion. The crystals are separated and stored in a refrigerator under N2.
E ~ ~ F ~
2,2'-Diketospirilloxanthin [ 2 4 0 0 9 - 1 7 - 4 1 M 624.9, m 225-227O, 550(349nm), Purified by 820(422nm), 2125(488nm), 2725(516nm), 2130(551nm) in hexane. chromatography on a column of partially deactivated alumina. Crystd from acetone/pet ether. Stored in the dark, in an inert atmosphere at Oo. Dilauroyl peroxide [105-74-81 M 398.6, m 53-55O. EXPLOSIVE.
Crystd from n-hexane.
Potentially
Dilituric acid see 5-N-nitrobarbituric acid. Dimedone [126-81-81 M 140.2, m 148-149O. Crystd from acetone (ca 8ml/g), water or aqueous EtOH. Dried in air. 1,2-Dimercapto-3-propanol [59-52-91 M 124.2, b 82-84°/0.8mm, d 1.239, n 1.5732, 1,3-Dimercapto-2-propanol[584-04-31 M 124.2, b 82°/1.5mm. Ppted as the mercury mercaptide (see Bjoberg B 75 13 19421, regenerated with HzS, and distd at 2.7mm [Rosenblatt and Jean AC 951 19551.
m e s o -2,3-Dimercaptosuccinic acid [304-55-21 M 182.2, m 191-192O (dec), 210° (dec), 210-211O (dec). Purified by dissolving in NaOH and precipitating with dilute HCI, dry and recrystallise from MeOH. It has pKa values of 3.0 and 3.9, and the IR has v at 2544 (SH) and 1689 (C02H) cm-'. The bis-S-ace@ deriv has m 183-185O (from EtOAc or Me2CO) and its Me ester has m 119-120° (from pet ether) [Gerecke et al. HCA 44 957 1961; Owen and Sultanbawa JCS 31 12 19491.
4,4'-Dimethoxyazobenzene [2396-60-31 M 242.3, m 162.7-164.7O. Chromatographed on basic alumina, eluted with benzene. Crystd from 2:2: 1 (v/v) methanoVethanoUbenzene. 4,4'-Dimethoxyazoxybenzene [1562-94-31 M 258.3, m 165O. Crystd from hot 95% EtOH, dried, then sublimed in a vacuum onto a cold finger. 3,4-Dimethoxybenzaldehyde
see veratraldehyde.
o-Dimethoxybenzene (veratrole) [91-16-71 M 137.2, m 23O, b 208.5-208.7, d 1.085, n25 1.53232. Steam distd. Fractionally distd from BaO, CaH2 or Na. Crystd from benzene or low-boiling pet ether at Oo. Fractionally crystd from its melt. Stored over anhydrous Na2S04. m-Dimethoxybenzene [151-10-01 M 137.2, b 212-213O, d 1.056, n 1.5215. aqueous NaOH, and water, then dried. Fractionally distd from BaO or Na.
Extracted with
p-Dimethoxybenzene [150-78-71 M 137.2, m 57.2-57.8O. Steam distd. Crystd from benzene, MeOH or EtOH. Dried under vacuum. Also sublimes under vacuum. 2,4-Dimethoxybenzoic acid [91-52-11 M 182.2, m 109O, 2,6-Dimethoxybenzoic acid [1466-76-81 M 182.2, m 186-187O. Crystd from water. 3,4-Dimethoxybenzoic acid [93-07-21 M 182.2, m 181-182O. Crystd from water or aq acetic acid. 3,5-Dimethoxybenzoic acid [1132-21-41 M 182.2, m 185-186O. Crystd from water, EtOH or aq acetic acid.
188
Purification of Organic Chemicals
p,p'-Dimethoxybenzophenone [90-96-01 M 242.3, m 144.5O. Crystd from absolute EtOH.
2,6-Dimethoxybenzoquinone [530-55-21 M 168.1, m 256O. Crystd from acetic acid. Sublimes in a vacuum. 1,l-Dimethoxyethane (acetaldehyde dimethyl acetal) [534-15-6] M 90.1, b 212°/760mm, d 0.828, n 1.4140. Purified by GLC. 1,2-Dimethoxyethane (glyme). [110-71-41 M 90.1, b &lo, d 0.867, n 1.380. Traces of water and acidic materials have been removed by refluxing with Na, K or CaH2, decanting and distilling from Na, K, CaH2 or LiAlH4. Reaction has been speeded up by using vigorous high-speed stimng and molten potassium. For virtually complete elimination of water, 1,2-dimethoxyethane has been dried with Na-K alloy until a characteristic blue colour was formed in the solvent at Dry-ice/cellosolve temperatures: the solvent was kept with the alloy until distd for use [Ward JACS 83 1296 19611. Alternatively, glyme, refluxed with benzophenone and Na-K, was dry enough if, on distn, it gave a blue colour of the ketyl immediately on addition to benzophenone and sodium [Ayscough and Wilson JCS 5412 19631. Also purified by distn under N2 from sodium benzophenone ketyl (see above).
3,5-Dimethoxy-4-hydroxybenzaldehyde see syringaldehyde. 3,5-Dimethoxy-4-hydroxycinnamic acid see 3-(4-hydroxy-3,5-dimethoxyphenyl)acrylic acid.
5,6-Dimethoxy-l-indanone[2107-69-91 M 192.2, m 118-120°. Crystd from MeOH, then sublimed in a vacuum. D i m e t h o x y m e t h a n e (methylal) [ 1 0 9 - 8 7 - 5 1 M 76.1, b 42.3O, d 0.860, n15 1.35626, n 1.35298. The main impurity is MeOH, which can be removed by treatment with sodium wire, followed by fractional distn from sodium. The solvent is kept dry by storing in contact with molecular sieves. Alternatively, technical dimethoxymethane was stood with paraformaldehyde and a few drops of H2SO4 for 24h, then distd. It could also be purified by shaking with an equal volume of 20% NaOH, leaving for 30min, and distilling. Methods of purification used for acetal are probably applicable to methylal.
2,3-Dimethoxy-5-methyl-1,4-benzoquinone see Coenzyme Qo entry in Chapter 5 1,4-Dimethoxynaphthalene [10075-62-41 M 188.2, m 87-88O, 1,s-Dimethoxynaphthalene [10075-63-51 M 188.2, m 183-184O. Crystd from EtOH. 2,6-Dimethoxyphenol [9I-IO-I] M 154.2, m 54-56O. Purified by zone melting or sublimation in a vacuum. 3,4-Dimethoxyphenyl acetic acid (homoveratric acid) [93-40-31 M 196.2, m 97-99O. Crystd from water or benzenefligroin.
3,5-Dimethoxyphenylacetonitrile [13388-75-51 M 177.1. Crystd from MeOH. [Sankaraman et al. JACS 109 5235 19871. 4,4'-Dimethoxythiobenzophenone [958-80-5/ M 258.3, m 120O. Recrystd from a mixture of cyclohexane/dichloromethane(4: 1). 2,6-Dimethoxytoluene JACS 109 5235 19871.
[5673-07-41 M 152.2, m 39-41O. Sublimed in vucuo [Sankaraman et al.
4,4'-Dimethoxytrityl chloride (DMT) [40615-36-91 M 338.8, m 114O. Crysts from cyclohexaneacetyl chloride as the hydrochloride and dry over KOH pellets in a desiccator. When dissolved in C6H6 and air is blown through, HCI is removed. It crystallises from Et,O. [A 370 142 1909; B 36 2774 1903; Smith
189
Purification of Organic Chemicals
et al. JACS 84 430 1962; Smith et al. JACS 85 3821 19631. If it had hydrolysed considerably (see OH in IR) then repeat the crystallisation from cyclohexane-acetyl chloride - excess of AcCl is removed in vac over KOH.
Dimethyl acetal see 1,l-dimethoxyethane. N,N-Dimethylacetamide [ 1 2 7 - 1 9 - 5 1 M 87.1, b 58.0-58.5°/11.4mm, d 0.940, n 1.437. Shaken with BaO for several days, refluxed with BaO for lh, then fractionally distd under reduced pressure, and stored over molecular sieves. 94-Dimethylacrylic acid (senecioic acid) 1541-47-91 M 100.1, m 68O. Crystd from hot water or pet ether (b 60-80O). Dimethyl adipate [ 6 2 7 - 9 3 - 0 1 M 174.2, m 9-11°, b 109°/10mm, 1 2 1 - 1 2 3 ° / 2 0 m m , 23S0/760mm, dao 1.0642, nko 1.4292. Dissolve in Et20, wash with NaHC03, H20, dry over MgS04, filter, evaporate and distil several times until the IR and NMR are consistent with the structure [Lorette and Brown JOC 24 261 1959; Hoffmann and Weiss JACS 79 4759 19.571. Dimethyl adipimidate dihydrochloride [14620- 72-51 M 245.1, m 218-220°, 222-224O. If the salt smells of HCl then wash with MeOH and dry Et2O (1:3) under N2 until the HCl is completely removed. Recryst from MeOH-Et20 (it is very important that the solvents are super dry) [Hartman and Wold Biochemistry 6 2439 1967; McElvain and Shroeder JACS 71 40 19491. Dimethylamine [124-40-41 M 45.1, fp -92.2O, b 0°/563mm, 6.9O/760mm. through a KOH-filled tower, or using sodium at Oo during 18h.
Dried by passage
Dimethylamine hydrochloride [506-59-21 M 81.6, m 171O. Crystd from hot CHC13 or abs EtOH. Also recrystd from MeOWether soln. Dried in a vacuum desiccator over H2SO4, then P2O5. Hygroscopic.
p-Dimethylaminoazobenzene (Methyl Yellow) [60-11-71 M 225.3, m 118-119O(dec). Crystd from acetic acid or isooctane, or from 95% EtOH by adding hot water and cooling. Dried over KOH under vacuum at 50°. CARCINOGEN. p-Dimethylaminobenzaldehyde (Ehrlich's Reagent) [100-10-7] M 149.2, m 74-75O. Crystd from water, hexane, or from EtOH (2ml/g), after charcoal treatment, by adding excess of water. Also dissolved in aqueous acetic acid, filtered, and ppted with ammonia. Finally recrystd from EtOH.
p-Dimethylaminobenzoic EtOH/water.
acid [ 6 1 9 - 8 4 - 1 1 M 165.2, m 242.5-243S0(dec). Crystd from
p-Dimethylaminobenzophenone [530-44-91 M 225.3, m 92-93O. Crystd from EtOH. N , N - dimethy lamino-p- -chlorobenzene (B, -c hloro-N, N - dimethylaniline) [698-69-11 M 155.6, m 32-33So,35S0, b 231°/atm. Purified by vacuum sublimation [Guarret al. JACS 107 5104 19851. The picrate has m 126-128O (from methanol).
2S,3R-(+)-4-Dimethylamino-1,2-diphenI-3-methyl-2-butanol 138345-66-31 M 283.4, m 55*oy ~ (c 9.6, EtOH). Purification 57O, [a]*!46+9.3 (c 9.6, EtOH), [ a ] +7.7 of the hydrochloride by dissolving 1.5g in 13.5 ml of 5N HCl heating to boiling and evaporate in a vacuum. Recrystn of the 'HCI three times from MeOH-EtOAc gives m 189-190°, [aID-33.7O(c 1, H20) (enantiomer has +34.2O}. The 'HCI in the minimum volume of water is basified with aqueous 5N NaOH and extracted with EtZO. The extract is dried (K2C03)and evap leaving a residue which is stored in a desiccator over solid KOH as a low melting solid. It can be recovered with these procedures from asymmetric reductions with LAH, and reused. [JACS 77 3400 1955; JOC 28 2381 2483 19631.
190
Purification of Organic Chemicals
df-4-Dimethylamino-2,2-diphenylvaleramidel5985-87-51 M 296.4, m 183-184O. Crystd from aqueous EtOH. (-)-L-4-Dimethylamino-2,2-diphenylvaleramide [6078-64-41 M 296.4, 136.5-137.5O. Crystd from pet ether or EtOH. 2-Dimethylaminoethanol [108-01-0] M 89.1, b 134.5-135S0, d 1.430, n 1.4362. Dried with anhydrous K2CO3 or KOH, and fractionally distd. 6-Dimethylaminopurine [938-55-61 M 163.1, m 257O, 257.5-258.5O, 259-262O, 263-264O. It is purified by recrystn from H20, EtOH (0.32g in 101111) or CHC13. It has pKa values of 3.87 and 10.5 (H20, 25O) [Albert and Brown JCS 2060 1954; UV: Mason J C S 2071 19541. The monohydrochloride crystallises from EtOH-EtzO, m 253O (dec) [Elion et al. JACS 74 41 1 19.521,the dihydrochloride has m 225O (dec) and the picrate has m 245O (235-236.5O) [Fryth et al. JACS 80 2736 19581. 4-Dimethylaminopyridine [I 122-58-31 M 122.2, m 108-109O, b 191O. Recrystd from toluene [Sadownik et al. JACS 108 7789 19861. N,N-Dimethylaniline [121-69-71 M 121.2, f.p.2O, b 84°/15mm, 193°/760mm, d 0.956, n25 1.5556. Primary and secondary amines (including aniline and monomethylaniline) can be removed by refluxing for some hours with excess acetic anhydride, and then fractionally distilling. Crocker and Jones (JCS 1808 1959)used four volumes of acetic anhydride, then distd off the greater part of it, and took up the residue in ice-cold dil HCl. Non-basic materials were removed by ether extraction, then the dimethylaniline was liberated with ammonia, extracted with ether, dried, and distd under reduced pressure. Metzler and Tobolsky (JACS 76 5178 1954) refluxed with only 10% (w/w) of acetic anhydride, then cooled and poured into excess 20% HCI, which, after cooling, was extracted with ethyl ether. (The amine hydrochloride, remains in the aqueous phase.) The HCI s o h was cautiously made alkaline to phenolphthalein, and the amine layer was drawn off, dried over KOH and fractionally distd under reduced pressure, under nitrogen. Suitable drying agents for dimethylaniline include NaOH, BaO, CaS04, and CaH2. Other purification procedures include the formation of the picrate, prepared in benzene s o h and crystd to constant melting point, then decomposed with warm 10% NaOH and extracted into ether: the extract was washed with water, and distd under reduced pressure. The oxalate has also been used. The base has been fractionally crystd by partial freezing and also from aq 80% EtOH then from absolute EtOH. It has been distd from zinc dust, under nitrogen. 2,6-Dimethylaniline [87-62-71 M 121.2, f.p. 1l0, b 210-211°/736mm, d 0.974, n 1.5604. Converted to its hydrochloride which, after recrystn, was decomposed with alkali to give the free base. Dried over KOH and fractionally distd. 3,4-Dimethylaniline [95-64-71 M 121.2, m 51°, b 116-118°/25mm, b 226O/760mm. from ligroin and distilled under vacuum.
Crystd
9,lO-Dimethylanthracene [781-43-11 M 206.3, m 180-18lo., Crystd from EtOH, and by recrystn from the melt. 1,3-Dimethylbarbituric acid [769-42-61 M 156.1, m 123O. Crystd from water and sublimed in a vacuum. Also purified by dissolving log in lOOml of boiling CCldCHC13 (8:2) ( l g charcoal), filtered and cooled to 25O. Dried in vucuo [Kohn et al. A C 58 3184 19861. 7,12-Dimethylbenz[a]anthracene [57-97-61 M 256.4, m 122-123O. Purified by chromatography on alumina/toluene or benzene. Crystd from acetone/EtOH. 5,6-Dimethylbenzimidazole[582-60-51 M 146.2, m 205-206O. Crystd from ethyl ether. Sublimed at 140°/3mm. Next Page
