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Purification of Organic Chemicals

bisulphite compound which, after decomposing with excess NaHCO3 soln, was steam distd, extracted under N2 into ether and, after drying, the extract was fractionally distd [Kyte, Jeffery and Vogel JCS 4454 19601.

Butyramide [514-35-51 M 87.1, m 115O, b 230O. Crystd from acetone, benzene, CC14-pet ether, 20% EtOH or water. Dried under vacuum over P2O5, CaC12 or 99% H2S04. n-Butyric acid [107-92-61 M 88.1, f.p. -5.3O, b 163.3O, d 0.961, n 1.39796, n25 1.39581. Distd, mixed with KMnO4 (20g/L,), and fractionally redistd, discarding the first third [Vogel JCS 1814 19481. n-Butyric anhydride [106-31-01 M 158.2, b 198O, d 0.968. Dried by shaking with P2O5, then distd. y-Butyrolactone [96-48-01 M 86.1, b 83.8°/12mm, d 1.124. Dried with anhydrous CaS04, then fractionally distd. Handle in a fume cupboard due to TOXICITY. Butyronitrile [109-74-01 M 69.1, b 117.9O, d 0.793, n 1.3846, n30 1.37954. Treated with conc HCl until the smell of the isonitrile had gone, then dried with K2CO3 and fractionally distd [Turner JCS 1681 19561. Alternatively it was twice heated at 75O and stirred for several hours with a mixture of 7.7g Na2C03 and 11.5g KMn04 per L of butyronitrile. The mixture was cooled, then distd. The middle fraction was dried over activated alumina. [Schoeller and Wiemann JACS 108 22 19861.

Cactheline

(2,3-dihydro-4-nitro-2,3-dioxo-9,lO-~ecostrychnidin-lO-oicacid) [56120-61 M 508.4. Yellow crystals from H20. It is then dried over H2SO4 which gives the dihydrate, and in a vacuum over H2SO4 at 105O to give the anhydrous compound. The hydrochloride separates as the hydrate (on heating in vacuum at 80°) in orange-yellow prisms or plates, m 250°(dec), and forms a resorcinol complex which gives brown crystals from EtOH, m 325O, and a hydroquinone complex as dark red crystals from EtOH, m 319O. [ B 43 1042 1910,86 232, W: 242 1953; complexes: Gatto Gazetta Chim Ital 85 1441 19551.

Caffeic acid [331-39-51 M 180.2, m 195O. Crystd from water. Caffeine [58-08-2] M 194.2, m 237O. Crystd from water or absolute EtOH. (+)-Calarene (+ P-gurjunen, 1,3,3,11-tetramethyltricyclo[5.4.O.O2~4]undecan-7-ane, (la)1,1,7c,7ac-tetramethyl-la,2,3,5,6,7,7a,7b-octahydro-l~-cyclopropa[~]naphthalene, new name l(l0)aristolene) [I 7334-55-31 M 204.35, b 45-47°/0.008-0.01mm, 255-25S0/atm, diO 0.9340, n v 1.55051, [01]2,0 + 5 8 O (EtOH), +81.S0 (neat). Purified by gas chromatography (7% propylene glycol adipate on unglazed tile particles of size 0.2-0.3mm, 400 cm column length and 0.6 cm diameter, at 184O, with N2 carrier gas at a flow rate of 0.54 ml/sec using a Griffith and George T ~ FIIA thermal detector). Also purified by chromatography on alumina (200 times the weight of calarene) and eluted with pet 200 and 210 nm (E 9560, 5480) in EtOH. [IR: Sorm Coll Czech Chem Comm 18 512 ether. UV: ,A 1953,29 795 1964; TET LETT 827 1962, 225 19631. Calcein [1461-15-01 M 622.5. Free acid crystd from 50% aq MeOH, or 300mg sample in minimum amount of 0.1M NaOH, add 50ml 10-20% aqueous MeOH and filter. To the filtrate add 1M HCl to adjust to pH 2.5. Refrigerate overnight and filter on a No 4 glass filter. Wash well with MeOH and dry in vacuo. [Wallach et al. AC 31 456 19591. Calcon carboxylic acid [3737-95-91 M 428.4, m 300O. Purified through its p-toluidinium salt. The dye was dissolved in warm 20% aq MeOH and treated with p-toluidine to ppte the salt after cooling. Finally recrystd from hot water. [Itoh and Ueno Analyst 95 583 19701. Calmagite [3147-14-61 M 358.4, m 300O. Crude sample was extracted with anhydrous ethyl ether [Lindstrom and Diehl AC 32 1123 19601.

Purification of Organic Chemicals

133

Campesterol (24R-24-methylcholest-5-en-3P-ol)[474-62-41 M 400.7, m 156-159O, 157158O, [a]?-35.lo (c 1.2, CHCl3). Recryst twice from hexane and once from Me2C0. The benzoyf derivative has m 158-160° [ a g 3-8.6O ( CHC13), the acetyf derivative has m 137-138O (from EtOH) and [ a g 3 -35.1' (C 2.9, CHC13) [JACS 63 1155 19411. lR,4S-(-)-Camphanic acid [13429-83-91 M 198.2, m 190-192O, 198-200°, [a]$, -22.5O (c 1, dioxane), -4.4O (c 8, EtOH). Dissolve in CH2C12, dry (MgS04), filter, evaporate and residue is sublimed at 120°/0.5mm or 140°/1mm. [HCA 61 2773 19781. 1R,4S-(-)-Camphanic acid chloride [39637-74-61 M 216.7, m 65-66.5", 70.5-71°, [a]548 -23" (c 2, CC14), -7.5" (c 0.67, benzene). Soluble in toluene (50g/100ml at 0') and crysts from pet ether (b 40-60°). It sublimes at 7Oo/5mm, Store dry at Oo, v (CCl4) 1805s and 1780m cm-l. [JCSDT 2229 19761. RS-Camphene [565-00-41 M 136.2, m 51-52O, b 40-70°/10mm. Crystd twice from EtOH, then repeatedly melted and frozen at 30mm pressure. [Williams and Smyth JACS 84 1808 19621. Alternatively it is dissolved in Et20, dried over CaC12 and Na, evaporated and the residue sublimed in a vacuum [NMR: B 111 2527 19781. (-)-Camphene (1s -2,2-dimethyl-3-methylene norbornane) [5794-04 - 71 M 136.2, m 49.249.6O, 49-50°, b 79-80°/58mm, 91.5°/100mm, d i 4 0.8412, n y 1.4564, [a]i5-106.2O (c 40, C6H6), -117.5O (c 19, toluene), -113.5O (c 9.7, Et2O). Purified by fractionation through a Stedman column at lOOmm in a N2 atmosphere, crystallised from EtOH and sublimed in a vacuum below its melting point. It is characterised by its camphenifone semicarbazone, m 217-2 18S0, or camphor semicarbazone, m 236-238O. [NMR: B 111 2527 1978; A 623 217 1959; Bain et al. JACS 72 3124 19501 R-(+)- [464-49-31 and S - ( - ) - [464-48-21 C a m p h o r (1R-bornan-2-one) M 136.2, m 178.8O, 179.97O(open capillary), b 204O/atm, [ a ] z z 6 f59.6O (in EtOH), [a]iof44.3O (c 10, EtOH), [a]:;; f70.8S0 (melt). Crystd from EtOH, 50% EtOWwater, MeOH, or pet ether or from glacial acetic acid by addition of water. It can be sublimed (50°/14mm) and also fractionally crystd from its own melt. It is steam volatile. It should be stored in tight containers as it is appreciably volatile at room temperature. The solubility is 0.1% (H20), 100% (EtOH), 173% (Et2O) and 300% (CHC13). The R-oxime (from Et20, CHC13, or dil EtOH) m 119O [a]io-42.40 (c 3, EtOH); the f oxime has m 118-1 19O. [B 67 1432 1934; Allan and Rodgers JCS ( B ) 632 1971; UV, NMR: Fairley et al. JCS Perkin Trans I 2109 1973; JACS 62 8 19401. ( I R , 2 S ) - ( + ) - [ 1 2 4 - 8 3 - 4 1 and ( I S , 2 R ) - ( - ) - [560-09-91 C a m p h o r i c acid ( 1 , 2 , 2 t r i m e t h y Ic y c lop en t a n - lr,3c -dicarboxylic acid) M 200.2, m 186-188O, 187O, 186.5- 189O, 20 [a]546 f57O (c 1, EtOH), [a];' f47.7O (c 4, EtOH). Purified by repptn from an alkaline s o h by HCI, filtered, and rerystd from water several times, rejecting the first crop. It forms leaflets from EtOH and Me2CO and H20 and is insol in CHC13. Sol in H20 is 0.8% at 25O and 10% at 100O; 50% (EtOH) and 5% in ethylene glycol. The (*)-acid has m 202-203O. The (+)-I-methylester had m 86O (from pet ether) [ a g + 4 5 O (c 4, EtOH), and the (+)-3-methyfester has m 77O (from pet ether) [ai7"+53.9O (c 3, EtOH). [JACS 5 3 1661 1931; HCA 30 933 1947;Acta Chem Scand 2 597 19481. The acid has pKa values of 4.71 and 5.83 in H20 [JACS 80 6316 19581. (+)-Camphoric anhydride [595-30-21 M 182.2, transition temp 135O, m 223.5O. Crystd from EtOH. (IR)-(-)- [10334-26-61 ( l S ) - ( + ) - [2767-84-21 Camphorquinone (borna-2,3-dione) M 166.2, m 198.7O, 198-199O, 197-201°, [ a ] ~ + l O l . l o (c 2, EtOH). It can be purified by steam distillation, recrystn (yellow prisms) from EtOH, C6H6 or Et20-pet ether and can be sublimed in a vacuum. The (5)quinone forms needles from EtOH, m 197-19S0, 203O. [HCA 13 1026; B 67 1432 19341.

(1R)-(-)Camphor-10-sulphonic acid [35963-20-31 M 232.3, m 197.4-198O(dec), 197-198O, [a];' -20.7O (c 5.4, H20). Forms prisms from AcOH or EtOAc, and is deliquescent in moist air. Store

134

Purification of Organic Chemicals

i n tightly stoppered bottles. The NH4 salt forms needles from H20 [ag6f20.5O (c 5, H20). [ J C S 127 279 1925 ;JACS 78 3063 19561.

[~~]2540~

(IS)-(+)Camphor-10-sulphonic acid [3144-16-91 M 232.3, m 193O(dec), 197-198O, +27.50 (c 10, HzO), [a]:' +43.5O (c 4.3, EtOH). Crystd from ethyl acetate and dried under vacuum.

( I S ) - ( + ) - /21286-54-41 and (ZR)-(-)[39262-22-11 Camphor-10-sulphonyl chloride M 250.7, m 67-68O, 70°, [CX]:' f32.2O (c 3, CHCI3). If free from OH bands in the IR then recryst from Et20 or pet ether, otherwise treat with SOCI;?at 50° for 30min, evaporate, dry residue over KOH in a vacuum and recrystallise. The (&)-acid chloride has m 8 5 O . Characterised as the amide (prisms from EtOH) m 132O, [ag' * I S 0 (EtOH). [Read and Storey JCS 2761 1930; JACS 58 62 19361. S-Canavanine [543-38-41 M 176.2, m 184O, [a]lD7 +19.4O (c 2, H , 2% S-Canavanine sulphate [2219-31-01 M 274.3, m 172O(dec), [aID +17.3O (c 3.2, Crystd from aqueous EtOH.

H20).

Cannabinol [521-35-71 M 310.4, m 76-77O, b 18S0/0.05mm. Crystd from pet ether. Sublimed.

&;Trn

Canthaxanthin (trans) [514-78-31 M 564.9, m 211-212O, 2200 (470nm) in cyclohexane. Purified by chromatography on a column of deactivated alumina or magnesia, or on a thin layer of silica gel G (Merck), using dichloromethane/ethyl ether (9: 1) to develop the chromatogram. Stored in the dark and in an inert atmosphere at -2OO. Capric acid (decanoic acid) [334-48-51 M 172.3, m 31S0, b 148°/11mm, d 0.8858, n25 1.4239. Purified by conversion to its methyl ester, b 114.0°/15mm (using excess MeOH, in the presence of H2SO4). After removal of the H2SO4 and excess MeOH, the ester was distd under vacuum through a 3ft column packed with glass helices. The acid was then obtained from the ester by saponification. [Trachtman and Miller JACS 84 4828 19621. n-Caproamide [628-02-41 M 115.2, m looo. Crystd from hot water. Caproic acid [142-62-1] M 116.2, b 205.4O, d 0.925, n 1.4168. fractionally distilled from CaS04.

Dried with MgS04 and

E-Caprolactam (azepan-2-one, aza-2-cycloheptanone) [ I 05-60-21 M 113.2, m 70°, 70.571S0, 70-71°, 262S0/760mm. Distd at reduced pressure, crystd from acetone or pet ether and redistd. Purified by zone melting. Very hygroscopic. Discolours in contact with air unless small amounts (0.2g/L) of NaOH, Na2C03 or NaB02 are present. Crystd from a mixture of pet ether (185ml of b 70°) and 2-methyl-2propanol (30ml), from acetone, or pet ether. Distd under reduced pressure and stored under nitrogen. [S 614 19781. Capronitrile [124-12-91 M 125.2, b 163.7O, n 1.4069, nZ5 1.4048. Washed twice with halfvolumes of conc HCl, then with saturated aqueous NaHC03, dried with MgS04, and distilled. Caprylic acid see n-octanoic acid. Caprylolactam (azanon-2-one, azacyclononan-2-one, 8-aminooctanoic acid lactam) [935-30150-151°/7-8mm, 164O/14mm, di3 1.0087, :n 1.4889. Dissolve in CHC13, decolorise with charcoal, evaporate to dryness and recrystallise from CHC13-hexane. Sublime at high vacuum. pKa25 0.55 in AcOH. The oxime has m 117O (from C6H6 or pet ether). [J Med Chem 14 501 1971; A 607 67 19571.

81 M 141.2, m 72O, 73O, 74-76O, 75O, 76-77O, b 119-122°/0.7mm,

Capsaicin (E-N-[(4-hydroxy-3-methoxyphenyl)-methyl]-8-methyl-6-nonenamide) [404-86-41 M 305.4, m 64-66O, 65O, 66.1°, b 210-220°/0.01mm. Recrystd from pet ether (b 40-60°), or pet ether-Et20 (9:1). Also purified by chromatography on neutral A1203 (grade V) and eluted successively with

Purification of Organic Chemicals

135

C6H6, C&j-EtOAc (17:3) and C,&-EtOAc (7:3), and distilled at 120°/10-5mm, and repeatedly recrystd from isopropanol (charcoal), needles. [JCS 11025 1955, JCS(C) 442 19681.

Capsorubin 1470-38-21 M 604.9, m 21S0, ,A 443, 468, 503 nm, in hexane. Possible impurities: zeaxanthin and capsanthin. Purified by chromatography on a column of CaC03 or MgO. Crystd from benzene/pet ether or CS2. Captan [133-06-21 M 300.5, m 172-173O. Crystd from CCl4. Captopril (S-l-[3-mercapto-2-methyl-l-oxopropyl]-L-proline) [62571-86-21 M 217.3, m 103-104°(polymorphic unstable form m 86O, melts at 87-88O solidifies and then melts again at 104-105O), -131O (c 1.7, EtOH). Purified by recrystn from EtOAc-hexane. Also purified by dissolving in EtOAc and chromatographed on a column of Wakogel C200 using a linear gradient of MeOH in EtOAc (O-lOOo)and fractions which give a positive nitropmsside test (for SH) are combined, evap and recrystd from EtOAc-hexane (l:l), white crystals [ag0-128.20 (c 2.0, EtOH). It has pKa values of 3.7 and 9.8 in H20. [Nam J Pharm Sci 73 1843 19841. Alternatively, dissolve in H20, apply to a column of AG-50Wx2 (BioRad) and eluted with H20. The free acid is converted to the dicyclohexylamine salt in MeCN by addition until the pH is 8-9 (moist filter paper). The salt is converted to the free acid by shaking with EtOAc and 10% aq KHS04 or passage through an AG50Wx2 column. The EtOAc soln is dried (MgS04) and recrystd as above from EtOAc-hexane [BJ 16 5484 1977; NMR and IR: Horii and Watanabe J Pharm SOC Japan 81 1786 19611.

[a]y

4-(Carbamoylmethoxy)acetanilide [14260-41-41 M 208.2, m 208O. Crystd from water. 3-Carbamoyl-1-methylpyridinium chloride [1005-24-91 M 172.6. Crystd from MeOH

Carbanilide [102-07-81 M 212.3, m 242O. Crystd from EtOH or a large volume (40mYg) of hot water. 9-Carbazolacetic acid [524-80-11 M 225.2, m 215O. Crystd from ethyl acetate Carbazole [86-74-81 M 167.2, m 240-243O. Dissolved (60g) in conc H2SO4 (300ml), extracted with three 200ml portions of benzene, then stirred into 1600ml of an ice-water mixture. The ppte was filtered off, washed with a little water, dried, crystd from benzene and then from pyridinelbenzene. [Feldman, Pantages and Orchin JACS 73 4341 19511. Has also been crystd from EtOH or toluene, sublimed in vacuum, zone-refined, and purified by TLC. Carbazole-9-carbonyl chloride [73500-82-0] M 300.0, m 100-103°, 103.5-104S0. Recrystd from C6H6. If it is not very pure (presence of OH or NH bands in the IR) dissolve in pyridine, shake with phosgene in toluene, evaporate and recrystallise the residue. Cany out this experiment in a good fume cupboard as COC12 is very TOXIC, and store the product in the dark. It is moisture sensitive. The amide has m 246.5-247O, and the dimethylaminoethylamide hydrochloride has m 197- 198O. {Weston et al. JACS 75 4006 19531.

4 - C a r b o e t h o x y - 3 - m e t h y l - 2 - c clohexen-1-one { 4 8 7 - 5 1 - 4 1 M 182 , b 79-80°/0.2mm, 121Yo 123"/4mm, 142-144°/15mm, d4 1.038. Dissolve in ether, shake with solid K2CO3, aqueous saturated NaHC03, dry (MgS04) and distil. Semicarbazone has m 165-167O (169O). [JACS 65, 631, 19431.

1-Carbethoxy-4-methylpiperazine hydrochloride

[532-78-51 M 204.7, m 168.5-169O. Crystd

from absolute EtOH.

N-Carboethoxyphthalimide [22509- 74-61 M 219.2, m 87-89O, 90-92O. Crystd from toluene-pet ether (or benzene-pet ether). Partly soluble in Et20, benzene and CHCI,. [ B 54 11 12 19211.

Carbitol see diethylene glycol monoethyl ether. Carbobenzoxy chloride

see benzyloxycarbonyl

chloride.

136

Purification of Organic Chemicals

y-Carboline [244-63-31 M 168.2, m 225O. Crystd from water. Carbon Black Leached for 24h with 1:1 HCI to remove oil contamination, then washed repeatedly with distd water. Dried in air, and eluted for one day each with benzene and acetone. Again dried in air at room temp, then heated in a vacuum for 24h at 6000 to remove adsorbed gases. [Tamamushi and Tam& TFS 55 1007 19591. Carbon disulphide [75-15-01 M 76.1, b 46.3O, d 1.264, n 1.627. Shaken for 3h with three portions of KMnO4 s o h ( 5 g L ) , twice for 6h with mercury (to remove sulphide impurities) until no further darkening of the interface occurred, and finally with a soln of HgS04 (2.5gL) or cold, satd HgC12. Dried with CaC12, MgS04, or CaH2 (with further drying by refluxing with P2O5), followed by fractional distn in diffuse light. Alkali metals cannot be used as drying agents. Has also been purified by standing with bromine (0.5mlL) for 3-4h, shaking with KOH soln, then copper turnings (to remove unreacted bromine), and drying with CaC12. CS2 is highly TOXIC and highly FLAMMABLE. Work in a good fumehood. Small quantities of CS2 have been purified (including removal of hydrocarbons) by mechanical agitation of a 4550g sample with a soln of 130g of sodium sulphide in 150ml of H20 for 24h at 35-40°. The aqueous sodium thiocarbonate s o h was separated from unreacted CS2, then ppted with 140g of copper sulphate in 350g of water, with cooling. After filtering off the copper thiocarbonate, it was decomposed by passing steam into it. The distillate was separated from H20 and distd from P2O5. [Ruff and Golla Zanorg Chem 138 17 19241. Carbon tetrabromide [558-13-41 M 331.7, m 92.5O. Reactive bromide was removed by refluxing with dilute aqueous Na2C03, then steam distd, crystd from EtOH, and dried in the dark under vacuum. [Sharpe and Walker JCS 157 19621. Can be sublimed at 70° at low pressure. Carbon tetrachloride [56-23-51 M 153.8, b 76.8O, d25 1.5842. For many purposes, careful fractional distn gives adequate purification. Carbon disulphide can be removed by shaking vigorously for several hours with saturated KOH, separating, and washing with water: this treatment is repeated. The CCl4 is shaken with conc H2SO4 until there is no further coloration, then washed with water, dried with CaCl2 or MgS04 and distd (from P2O5 if desired). It must not be dried with sodium. An initial refluxing with mercury for 2h removes sulphides. Other purification steps include passage of dry CC14 through activated alumina, and distn from KMn04. Carbonyl containing impurities can be removed by percolation through a Celite column impregnated with 2,4-dinitrophenylhydrazine(DNPH), H3P04 and water. (Prepared by dissolving 0.5g DNPH in 6ml of 85% H3P04 by grinding together, then mixing with 4ml of distd water and log Celite.) [Schwartz and Parks AC 33 1396 19611. Photochlorination of CCl4 has also been used: CC14 to which a small amount of chlorine has been added is illuminated in a glass bottle (e.g. for 24h with a 200W tungsten lamp near it), and, after washing out the excess chlorine with 0.02M Na2S03, the CCl4 is washed with distd water and distd from P2O5. It can be dried by passing through 4A molecular sieves and distd. Another purification procedure is to wash CC14 with aq NaOH, then repeatedly with water and N2 gas bubbled through the liquid for several hours. After drying over CaC12 it is percolated through silica gel and distd under dry N2 before use [Klassen and Ross JPC 91 3664 19871. Carbon tetrafluoride [75-73-01 M 88.0, b -15O. Purified by repeated passage over activated charcoal at solid-C02 temperatures. Traces of air were removed by evacuating while alternately freezing and melting. Alternatively, liquefied by cooling in liquid air and then fractionally distilled under vacuum. (The chief impurity originally present was probably CF3Cl). Carbon tetraiodide [507-25-51 M 519.6, m 168O(dec). Sublimed in vacuo. N,N'-Carbonyldiimidazole tetrahydrofuran, in a dry-box.

[530-62-11 M 162.2, m 115.5-116O.

Crystd from benzene or

l,l'-Carbonyldi(l,2,4-triazole) [41864-22-61 M 164.1, m 134-136O, 145-150O. Dissolve i n tetrahydrofuran and evaporate at lOmm until it crystallises. Wash crystals with cold tetrahydrofuran and dry in a vacuum desiccator over P2O5 in which it can be stored for months. [Rec Trav Chim Pays Bas 80 1372 1961; Potts JOC 27 263 1 1962; Staab A 106 75 19571.

Purification of Organic Chemicals

137

Carbonyl sulphide [463-58-I] M 60.1, b -47.5O. Passed through traps containing saturated aqueous lead acetate and then through a column of anhydrous CaS04. TOXIC. Carbostyril see 2-hydroxyquinoline.

(Carboxymethyl)trimethylammonium chloride hydrazide see Girard reagent T. o-Carboxyphenylacetonitrile [6627-91-41 M 161.2, m 114-115O. Crystd (with considerable loss) from benzene or glacial acetic acid. S-Carnosine, a - , p-, y-, and 5-Carotenes, A-Carrageenan see entries in Chapter 5. (-)-Caryophyllene oxide ( l - S - 5 c - 6 ~ - e p o x y - 6 c , l O , l O - t r i m e t h y l - 2 - m e t h y l e n e - l ~ , 9 f bicyclo[7.2.0]undecane) [ I I 2 { 9 - 3 O - 6 ] M 220.4, m 62-63O, 63.5-64O, 64O, b 114117°/1.8mm, 141-142°/11mm, d4 0.9666, nLo 1.49564, [a]?-79O (c 2,CHCI3), [a]Zd)-68O (supercooled melt). Purified by TLC on silica gel with EtOAc-pet ether (b 60-80°) (15:85), and recrystallised from MeOH or C6H6. [NMR: Warnhoff Cunad J Chem 42 1664 1964, Ramage and Whitehead JCS 4336 19541. Catechin [7295-85-41 M 272.3, m 177O (anhyd). Crystd from hot water. Dried at looo. Catechol [120-80-91 M 110.1, m 105O. Crystd from benzene or toluene. Sublimed under vacuum. [Rozo et al. AC 58 2988 19861. Cation exchange resin. Conditioned before use by successive washing with water, EtOH and water, and taken through two H+-Na+-H+ cycles by successive treatment with M NaOH, water and M HCl then washed with water until neutral. [Ion exchange resins, BDH Handbook, 5th edn 19711. (+)-Cedrol (octahydro-3,6,8,8-tetramethyl-l-3a,7-methanoazu~en-6-ol, 8aS-6c-hydroxy3c,6~,8,8-tetramethy1[8ar-H)-octahydro-3~,3af,7f-methanoazulene), m 82-86O, 86-87O, [a];' +10.So (c 5,CHC13), [a]b8+13.l0(c 5.5, EtOH), [a]',8+14.30 (c 10, dioxane). Purified by recrystn from aqueous MeOH. It is estimated colorimetrically with H3P04 in EtOH followed by vanillin and HCl [Hayward and Seymour AC 20 572 19481. The 3,5-dinitrobenzoyl derivative has m 92-93O. [JACS 83 31 14 19611. P-Cellobiose [528-50-71 M 342.3, m 228-229O(dec), [a&? +33.3O (c 2, water). 75% aqueous EtOH.

Crystd from

Cellosolve see 2-ethoxyethanol. Cellulose triacetate [9012-09-31 M 72,000-74,000. Extracted with cold EtOH, dried in air, washed with hot distd water, again dried in air, then dried at 50° for 30min. [Madorsky, Hart and Straus J Res Nut Bur Stand 60 343 19581. Cerulenin (helicocerin, 2R,3S-2,3-epoxy-4-oxo-7E,lOE-dodecadienamide) [17397-89-61 M 223.3, m 93-94', 93-95', b 120°/10-8mm, [a]k6+630 (c 2, MeOH). White needles from C6H6. Also purified by repeated chromatography from Fuoresil and silica gel. It is soluble in EtOH, MeOH, C6H6, slightly soluble i n H20 and pet ether. The dl-form has m 40-42O (from C&-hexane), and the 2R,3Stetrahydrocerulenin has m 86-87O, +44.4 (c 0.25, MeOH after 24h). [TET LETT2095 1978, 2039 1979; JACS 99 2805 1977; JOC 47 1221 19821.

[ago

Cetane see n-hexadecane.

138

Purification of Organic Chemicals

Cetyl acetate [629-70-91 M 284.5, m 18.3O. Vacuum distd twice, then crystd several times from ethyl ether/MeOH. Cetyl alcohol (1-hexadecanol) [36653-82-41 M 242.5, m 49.3O. Crystd from aqueous EtOH or from cyclohexane. Purified by zone refining. Purity checked by gas chromatography. Cetylamide [629-54-91 M 255.4, Cetylamine (1-hexadecylamine) [143-27-11 M 241.5, m 78O. Crystd from thiophene-free benzene and dried under vacuum over P2O5. Cetylammonium chloride [1602-97-71 M 278.0. Crystd from MeOH. Cetyl bromide (1-bromohexadecane) [ I 12-82-31 M 305.4, m 15O, b 193-196°/14mm. Shaken with H2SO4, washed with water, dried with K2CO3 and fractionally distd. Cetyl ether (4113-12-61 M 466.9, m 54O. Vacuum distd then crystd several times from MeOHhenzene. Cetylpyridinium chloride (H20) [6004-24-61 M 358.0, m 80-83O. Crystd from MeOH or EtOWethyl ether and dried in vucuo. [Moss et al. JACS 108 788 1986; Lennox and McClelland JACS 108 3771 19861. Cetyltrimethylammonium bromide (cetrimonium bromide) [124-03-81 M 364.5, m 22723S0(dec). Crystd from EtOH, EtOH/benzene or from wet acetone after extracting twice with pet ether. Shaken with anhydrous ethyl ether, filtered and dissolved in a little hot MeOH. After cooling in the refrigerator, the ppte was filtered at room temperature and redissolved in MeOH. Anhydrous ether was added and, after warming to obtain a clear soln, it was cooled and crystalline material was filtered. [Duynstee and Grunwald JACS 81 4540 1959; Hakemi et al. JACS 91 120 19871. Cetyltrimethylammonium chloride [ I 12-02-71 M 320.0. EtOWether, or from MeOH. [Moss et al. JACS 109 4363 1987.

Crystd from acetone/ether mixture,

Chalcone see benzalacetophenone. Charcoal. Charcoal (50g) was added to 1L of 6M HCl and boiled for 45min. The supernatant was discarded, and the charcoal was boiled with two more lots of HCl, then with distilled water until the supernatant no longer gave a test for chloride ion. 'The charcoal (which was now phosphate-free) was filtered on a sintered-glass funnel and air dried at 120° for 24h. [Lippin, Talbert and Cohn JACS 76 2871 19541. The purification can be carried out using a Soxhlet extractor (without cartridge), allowing longer extraction times. Treatment with conc H2S04 instead of HCl has been used to remove reducing substances. Chaulmoogric acid [502-30-71 M 280.4, m 68S0, b 247-248O/20mm. Crystd from pet ether or EtOH. Chelerythrine [2870-15-71 M 389.4, m 207O. Crystd from CHC13 by addition of MeOH. Chelex 100 (11139-85-81. Washed successively with 2M ammonia, water, 2M nitric acid and water. Chelex 100 may develop an odour on long standing. This can be removed by heating to SOo for 2h in 3M ammonia, then washing with water. [Ashbrook JC 105 151 19751. Chelidamic acid see 4-hydroxypyridine-2,6-dicarboxylicacid. Chelidonic acid [6003-94-71 M 184.1, m 262O. Crystd from aqueous EtOH. Chenodesoxycholic acid [474-25-91M 392.6, m 143O, [a]$& +14O (c 2, EtOH). Crystd from ethyl acetate.

139

Purification of Organic Chemicals

Chimyl alcohol (1-U-n-hexadecylglycerol)[6145-69-31 M 316.5, m

64O.

Crystd from hexane.

Chloral [75-87-61 M 147.4, b 98O. Distd, then dried by distilling through a heated column of CaS04. Chloralacetone chloroform [512-47-01 M 324.9, m 65O. Crystd from benzene. a-Chloralose (R-1,2-U-[2,2,2-trichloroethylidene]-a-D-glucofuranose)[15879-931 M 309.5, m 180-182O, 187O, 186-188O,[a]i6 +19S0 (c 11, pyridine). Recrystd from EtOH, 38% aqueous EtOH, Et20, H20 or CHC13 The solubility is 0.44% in H20 at 15O, 0.83% in H20 at 37O, 6.7% in EtOH at 25O. [Whiton and Hixon JACS 55 2438 1933; HCA 6 621 19231. The p-isomer is less soluble in H20, EtOH or Et20 and has m 237.5-238O [JACS 59 1955 1937; Acta Chern Scand 19 359 19653. 2-Chloroacetophenone [532-27-41 M 154.6, m 54-56O. Crystd from MeOH [Tanner JOC 52 2 142 19871. Chlorambucil [305-03-31 M 304.2, m 64-66O. Crystd from pet ether. Chloramphenicol [56-75-71 M 323.1, m 150.5-151S0,[a]:!, +25O (c 5, EtOH). Crystd from water (sol 2.5mgJml at 25O) or ethylene dichloride. Sublimed under high vacuum. Chloramphenicol from benzene.

palmitate [530-43-81 M 561.5, m 90°, [a]i6 +24.6O (c 5, EtOH).

Crystd

p-Chloranil (2,3,5,6-tetrachloro-1,4-benzoquinone)[ 1 1 8 - 7 5 - 2 1 M 245.9, m 290°, 294.2294.6O (sealed tube). Crystd from acetic acid, acetone, benzene, EtOH or toluene, drying under vac over P2O5, or from acetic acid, drying over NaOH in a vacuum desiccator. It can be sublimed under vacuum at 2900. Sample may contain significant amounts of the o-chloranil isomer as impurity. Purified by triple sublimation under vacuum. Recrystd before use. It is a skin and mucous membrane irritant. [W:Rec Trav Chirn Pays Bas 276 684 1924; Brook JCS 5040 19521. Chloranilic acid (2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone) [87-88- 71 M 209.0, m 2832 8 4 O . A s o h of 8g in 1L of boiling water was filtered while hot, then extracted twice at about 50° with 2OOml portions of benzene. The aq phase was cooled in ice-water. The crystals were filtered off, washed with three lOml portions of water, and dried at 115O. It can be sublimed in vacuum. pKa25 1.22 and 3.01 in H20 [JPC 61 765 1953. The diacetate has m 182-185O [JACS 46 1866 1924; Thamer and Voight JPC 56 225 19521. Chlorazol Sky Blue FF [2610-05-11 M 996.9. Freed from other electrolytes by adding aqueous sodium acetate to a boiling soln of the dye in distd water. After standing, the salted-out dye was filtered on a Buchner funnel, the process being repeated several times. Finally, the ppted dye was boiled several times with absolute EtOH to wash out any sodium acetate, then dried (as the sodium salt) at 105O. [McGregor, Peters and Petropolous TFS 58 1045 19621. Chlorendic anhydride

(1,4,5,6,7,7,-hexachloro-5-norbornene-2,3-dicarboxylicanhydride)

[115-27-51 M 370.9, m 234-236O. 235-237O,238O. Steam distn or recrystn from H20 yields the diacid. The purified diacid yields the anhydride with Ac20. [Prill JACS 69 62 19471.

Chloroacetaldehyde dimethyl acetal [ 9 7 - 9 7 - 2 1 M 124.6, m -34.4O, b 64°/23mm, 7172O/35mm, d:' 1.0172, n;' 1.4175. Purified by fractional distillation. [Melhotra JICS 36 4405 1959; Bull SOC Chirn Belges 61 393 19521. a-Chloroacetamide 179-07-21 M 93.5, m 121°, b 224-225O/743mm. Crystd from acetone and dried under vacuum over P2O5. p-Chloroacetanilide [539-03-71 M 169.6, m 179O. Crystd from EtOH or aqueous EtOH.

140

Purification of Organic Chemicals

Chloroacetic acid [79-11-81 M 94.5, m 62.S0, b 189O. Crystd from CHC13, CCl4, benzene or water. Dried over P2O5 or conc H2SO4 in a vacuum desiccator. Further purification by distn from MgS04, and by fractional crystn from the melt. Stored under vac or under dry N2. [Bernasconi et al. JACS 107 3621 19851. Chloroacetic anhydride [541-88-8] M 171.0, m 46O, d 1.5494. Crystd from benzene. Chloroacetone [78-95-51 M 92.5, b 119°/763mm, d 1.15. Dissolved in water and shaken repeatedly with small amounts of ethyl ether which extracts, preferentially, 1,l-dichloroacetone present as an impurity. The chloroacetone was then extracted from the aqueous phase using a large amount of ethyl ether, and distd at slightly reduced pressure. It was dried with CaC12 and stored at Dry-ice temperature. Alternatively, it was stood with CaS04, distd and stored over CaS04. LACHRYMATORY. Chloroacetonitrile [107-14-21 M 75.5, b 125O. Refluxed with P2O5 for one day, then distd through a helices-packed column. Also purified by gas chromatography. 1-Chloroadamantane see 1-adamantyl chloride. o-Chloroaniline [95-51-21 M 127.6, m -1.9O, b 208.S0, d 1.213, n 1.58807. Freed from small amounts of the p-isomer by dissolving in one equivalent of H2SO4 and steam distilling. The p-isomer remains behind as the sulphate. [Sidgwick and Rubie JCS 1013 19211. An alternative method is to dissolve in warm 10% HCl (1 lmVg of amine) and on cooling, the hydrochloride of o-chloroaniline separates out. The latter can be recrystd until the acetyl derivative has a constant melting point. (In this way, yields are better than for the recrystn of the picrate from EtOH or of the acetyl derivative from pet ether.) [King and Orton JCS 1377 19111. p-Chloroaniline [106-47-81 M 127.6, m 70-71O. Crystd from MeOH, pet ether (b 30-60°), or 50% aq EtOH, then benzenelpet ether (b 60-70°), then dried in a vacuum desiccator. Can be distd under vacuum (b 7577O/33mm). p-Chloroanisole [623-12-11 M 142.6, b 79°/11.5mm, 196.6°/760mm, d 1.164, n25-5 1.5326. Washed with 10% (vol) aqueous H2SO4 (three times), 10% aqueous KOH (three times), and then with water until neutral. Dried with MgS04 and fractionally distd from CaH2 through a glass helices-packed column under reduced pressure. 9-Chloroanthracene 1126 19861.

[716-53-01 M 212.9, m 105-107O. Crystd from EtOH.

[Masnori JACS 108

10-Chloro-9-anthraldehyde [10527-16-91 M 240.7, m 217-219O. Crystd from EtOH. o-Chlorobenzaldehyde [89-98-51 M 140.6. m 1l0, b 213-214O, d 1.248, n 1.566. Washed with 10% Na2C03 soln, then fractionally distd in the presence of a small amount of catechol. 3-Chlorobenzaldehyde [587-04-21 M 140.6, m 1S0, b 213-214O, d 1.241, n 1.564. Purified by low temperature crystn from pet ether (b 40-60O). 4-Chlorobenzaldehyde [104-88-11 M 140.6, m 47O. Crystd from EtOH/water (3: l), then sublimed twice at 2mm pressure at a temperature slightly above the melting point. Chlorobenzene [108-90-71 M 112.6, b 131.7O, d 1.107, n 1.52480. The main impurities are likely to be chlorinated impurities originally present in the benzene used in the synthesis of chlorobenzene, and also unchlorinated hydrocarbons. A common purification procedure is to wash several times with conc H2S04 then with aq NaHC03 or Na2C03, and water, followed by drying with CaC12, K2CO3 or CaS04, then with P2O5. and distn. It can also be dried with Linde 4A molecular sieve. Passage through, and storage over, activated alumina has been used to obtain low conductance material. [Flaherty and Stern JACS 80 1034 19581.

Purification of Organic Chemicals

141

4-Chlorobenzenesulphonyl chloride [98-60-21 M 211.1, m 53O, b 141°/15mm. Crystd from ether in powdered Dry-ice, after soln had been washed with 10% NaOH until colourless and dned with Na2S04.

4-Chlorobenzhydrazide [536-40-31 M 170.6, m 164O. Crystd from water. 2-Chlorobenzoic acid [ I 18-91-21 M 156.6, m 139-140°. Crystd successively from glacial acetic acid, aq EtOH, and pet ether (b 60-80O). Other solvents include hot water or toluene (ca 4mVg). Crude material can be given an initial purification by dissolving 30g in IOOml of hot water containing log of Na2CO3, boiling with 5g of charcoal for 15min, then filtering and adding 31ml of 1:l aq HCl: the ppte is washed with a little water and dried at 100". 3-Chlorobenzoic acid [535-80-8] M 156.6, m 154-156O, 15S0, d:5 1.496. Crystd successively from glacial acetic acid, aqueous EtOH and pet ether (b 60-80°). It also recrysts from C & , or EtzO-hexane, and sublimes at 5 5 O in a vacuum. The pKa25 is 3.70 (H20) [ A C 26 726 19541, and 5.25 (in 50% dimethylacetamide). The methyl ester has m 21°, b 231°/atm. The S-benzyl thiouronium salt has m 164165O (from EtOH) [Acta Chem Scand 9 1425 1955;JCS 1318 19601. 4-Chlorobenzoic acid [74-11-31 M 156.6, m 238-239O. Same as for m-chlorobenzoic acid. Has also been crystd from hot water, and from EtOH. 2-Chlorobenzonitrile [873-32-51 M 137.6, m 45-46O. benzene/pet ether (b 40-60°). 4-Chlorobenzophenone 108 7727 19861.

Crystd to constant melting point from

[134-85-01 M 216.7, m 75-76O. Recrystd for EtOH. [Wagner et al. JACS

2-Chlorobenzothiazole [615-20-31 M 169.6, m 21°, 90-91.4°/4mm, 135-136°/28mm, d i 0 1.303, n y 1.6398. It is purified by fractional distn in vacuo. The 2-chloro-3-methylbenzothiazolinium 2,4-dinitrobenzenesulphonate crystallises from Ac20, m 162-163O (dec). [JACS 73 4773 1951; JOC 19 1830 1954; JCS 2190 19301. o-Chlorobenzotrifluoride [88-16-41 M 180.6, b 152.3O, m-Chlorobenzotrifluoride [98-15-71 M 180.6, b 137.6O, p-Chlorobenzotrifluoride [98-56-61 M 180.6, b 138.6O. Dried with CaS04, and distd at high reflux ratio through a silvered vacuum-jacketed glass column packed with one-eight inch glass helices [Potter and Saylor JACS 73 90 19511.

2-Chlorobenzoxazole [615-18-91 M 153.6, b 95-96°/20mm, 198-202O/atm, di0 1.331, n y 1.570. Purified by fractional distn, preferably in a vacuum. [Siedel J Prakt Chem (2) 42 456 1890; JACS 75 712 19531. p-Chlorobenzyl chloride [104-83-61 M 161.0, m 28-29O, b 96°/15mm. Dried with CaS04, then fractionally distd under reduced pressure. Crystd from heptane or dry ethyl ether. LACHRYMATORY.

p-Chlorobenzylisothiuronium chloride [544-47-81 M 237.1, m 197O. Crystd from conc HCl by addition of water. 1-Chlorobutane see n-butyl chloride. 2-Chlorobutane [78-86-41 M 92.6, b 68S0, d 0.873, n25 1.3945. Purified in the same way as n butyl chloride. 2-(4-Chlorobutyl)-l,3-dioxolane [ I 1 8336-86-01 M 164.6, b 56-58°/0.1mm, d i 0 1.106, ng1.457. If the IR has a CHO band then just distil in vacuum. If it is present then dissolve in Et20, wash with H20, then saturated NaHC03, dry over MgS04, evaporate and distil. [JACS 73 1365 19511.

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