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142 Purification of Organic Chemicals
N-Chlorocarbonyl isocyanate {27738-96-11 M 105.5, m -6S0, b 63.6O/atm, di0 1.310.
Fractionally distd at atmospheric pressure using a 40cm column. TOXIC vupour use a good fume hood.
Store dry, v 2260 (NCO), 1818 (CO) and 1420 (NCO sym) cm-l. [B 106 1752 19751.
4-Chlorocinnamic acid [1615-02-71 M 182.6, m 243O, 248-250°, 249-251O. Recrystd from
EtOH or aq EtOH (charcoal). [Org Synth Coll Vol IV 731 1963, Walling and Wolfstin JACS 69 852 1947.
Chlorocresol see chloromethylphenol.
Chlorocyclohexane [542-18-71 M 118.6, b 142S0, d 1.00, n25 1.46265. Washed several times
with dilute NaHCO3, then repeatedly with distilled water. Dried with CaC12 and fractionally distd.
4-Chloro-2,6-diaminopyrimidine (2,4-diamino-6-chloropyrimidine) [ 156-83-21 M 144.6, m
198O, 199-202O. Purified by recrystn from boiling H20 (charcoal) as needles; also crystallises from Me2CO.
Its pKa25 in H20 is 3.57. [Buttner B 36 2232 1903; Roth JACS 72 1914 1950; W: JCS 3172 19621.
2-Chloro-1,4-dihydroxybenzene see
chloroquinol.
4-Chloro-3,5-dimethylphenol [88-04-01 M 156.6, m 115.5O. Crystd from benzene or toluene.
l-Chloro-2,4-dinitrobenzene [97-00-71 M 202.6, m 48-50°, 51°, 52-54O, 54O, b 31S0/atm,
d:* 1.697. Usually crystd from EtOH or MeOH. Has also been crystd from Et20, C6H6, CgH6-pet ether or
isopropyl alcohol. A preliminary purification step has been to pass its soln in benzene through an alumina
column. Also purified by zone refining. It exists in three forms: one stable and two unstable. The stable form
crysts as yellow needles from Et20, m 51°, b 315O/atm with some dec, and is sol in EtOH. The labile forms
also crystallises from Et20, m 43O, and is more soluble in organic solvents. The second labile form has m
27O. [Hoffman and Dame, JACS 41 1015 1919, Welsh JACS 63 3276 1941; JCS 2476 1957).
4-Chloro-3,5-dinitrobenzoic acid [ I 1 8-97-81 M 246.6, m 159-161O.
EtOH or benzene.
Crystd from EtOH/water,
2-Chloro-3,5-dinitropyridine [2578-45-21 M 203.5, m 62-6S0, 63-65O, 64O. Dissolve in
CHC13, shake with saturated NaHCO3, dry (MgS04), evaporate and apply to an A1203 column, elute with pet
ether (b 60-80°), evaporate and recryst from C6H6 or pet ether. [Chem Pharm Bull Japan 8 28 1960; Rec Trav
Chim Pays Bas 72 573 19531.
Chloroethane see ethyl chloride.
2-Chloroethanol [107-07-31 M 80.5, b 51.0°/31mm, 128.6°/760mm, d 1.201, d5 1.44380.
Dried with, then distd from, CaS04 in the presence of a little Na2C03 to remove traces of acid.
2-Chloroethyl bromide [107-04-01 M 143.4, b 106-108°. Washed with conc H2SO4, water, 10%
Na2C03 soln, and again with water, then dried with CaC12 and fractionally distd before use.
2-Chlorethyl chloroformate [627-11-21 M 143.0, b 52-54O/12mm, 50°/15mm, 153°/760mm,
d18 1.3760, nko 1.4460. Purified by fractional distn, preferably in a vacuum and stored in dry atmosphere.
[JCS 2735 19571.
1-(2-Chloroethyl)pyrrolidine hydrochloride [ 7250-67-11 M 170.1, m 167-170°, 173.5-174O.
Purified by recrystn from isopropanol-di-idopropyl ether (charcoal) and recrystallised twice more. The free base,
b 55-56O/1 lmm, 60-63O/23mm and 90°/56mm, is relatively unstable and should be converted to the
hydrochloride immediately, by dissolving in iso-propanol and bubbling dry HCl through the soh at Oo, and
filtering off the hydrochloride and recrystallising it. The picrate has m 107.3-107.8° (from EtOH), [Cason JOC
24 247 1959; JACS 70 3098 19481.

Purification of Organic Chemicals 143
2-Chloroethyl vinyl ether [IIO-75-81 M 106.6, b 109°/760mm, d 1.048, n 1.437. Washed
repeatedly with equal volumes of water made slightly alkaline with KOH, dried with sodium, and distd under
vacuum. TOXIC.
Chloroform [67-66-31 M 119.4, b 61.2O, d15 1.49845, d10 1.47060, n15 1.44858. Reacts
slowly with oxygen or oxidising agents, when exposed to air and light, giving, mainly, phosgene, C12 and HCl.
Commercial CHC13 is usually stabilized by addn of up to 1% EtOH or of dimethylaminoazobenzene. Simplest
purifications involve washing with water to remove the EtOH, drying with K2CO3 or CaC12, refluxing with
P2O5, CaC12, CaS04 or Na2S04, and distilling. It must not be dried with sodium. The distd CHC13
should be stored in the dark to avoid photochemical formation of phosgene. As an alternative purification,
CHC13 can be shaken with several small portions of conc H2SO4, washed thoroughly with water, and dried with
CaC12 or K2CO3 before filtering and distilling. EtOH can be removed from CHC13 by passage through a
column of activated alumina, or through a column of silica gel 4-ft long by 1.75-in diameter at a flow rate of
3ml/min. (The column, which can hold about 8% of its weight of EtOH, is regenerated by air drying and then
heating at 6Oo0 for 6h. It is pre-purified by washing with CHC13, then EtOH, leaving in conc H2SO4 for about
8hr, washing with water until the washings are neutral, then air drying, followed by activation at 600° for 6h.
Just before use it is reheated for 2h to 154O.) [McLaughlin, Kaniecki and Gray AC 30 1517 19581.
Carbonyl-containing impurities can be removed from CHC13 by percolation through a Celite column
impregnated with 2,4-dinitrophenylhydrazine, phosphoric acid and water. (Prepared by dissolving 0.5g DNPH in
6ml of 85% H3P04 by grinding together, then mixing with 4ml of distilled water and log of Celite.) [Schwartz
and Parks AC 33 1396 19611. Chloroform can be dried by distn from powdered type 4A Linde molecular
sieves. For use as a solvent in IR spectroscopy, chloroform is washed with water (to remove EtOH), then dried
for several hours over anhydrous CaC12 and fractionally distd. This treatment removes material absorbing near
1600 cm-l. (Percolation through activated alumina increases this absorbing impurity). [Goodspeed and Millson
Chemistry & Industry (London) 1594 19671.
Chlorogenic acid [327-97-91 M 354.3, m 208O. [a&,’ -36O (c 1, HzO). Crystd from water. Dried at
1 loo.
5-Chloro-8-hydroxy-7-iodoquinoline [I 30-26- 71 M 305.5, m 178-179O. Crystd from abs EtOH.
5-Chloroindole [I 7422-32-11 M 151.6, m 67-68O, 69-71°, 71.5-72S0, 72-73O, b 120-
130°/0.4mm. It is distd at high vacuum and recrystallises from pet ether (b 4G-6Oo) or (b 80-looo) as
glistening plates. The picrate has m 147O ( 146.5-147S0)(from C&). [JCS 3493 1955; JOC 44 578 19791.
4-Chloroiodobenzene [637-87-61 M 238.5, m 53-54O. Crystd from EtOH.
2,3-Chloromaleic anhydride [1122-17-41 M 166.9, m 112-115O. Purified by sublimation in
vacuum [Katakis et al. JCSDT 1491 19861.
4-(Chloromercuri)benzenesulphonic acid monosodium salt [I4110-97-51 M 415.2. The free
acid is obtained by acidifying an aq soln, filtering off the acid, washing it with H20 and recrystallising from hot
H20 to give a colourless solid which is dried in a vacuum over P2O5 and should give negative C1- ions. The Na
salt is made by dissolving in one equivalent of aqueous NaOH and evaporate to dryness. [B 67 130 1934;
JA CS 76 4331 19541.
5-Chloro-2-methoxyaniline (2-amino-4-chloroanisole) [95-03-41 M 157.6, m 81-83O, 82-
&lo, &lo. Purified by steam distn and recrystn from H20 or 40% aqueous EtOH. The N-acetare forms needles
from hot H20 m 104O; the N-benzoyl derivative forms needles from aq EtOH m 77-78O; the picrare has m
194O dec. [JACS 48 2657 19261.
9-Chloromethyl anthracene [24463-19-21 M 226.7, m 141-142O dec, 141-142.5O. If it is free
from OH in the IR then recryst from hexane-CgH,j or C6H6 as needles. If OH is present then some solvolysis
has occurred. In this case treat 8.5g with SOC12 (4.8g) in dioxane (6Oml) and reflux for 5h, then evaporate to

144 Purification of Organic Chemicals
dryness and wash the residue with cold C6H6 and recrystallise. With KI/Me2CO it forms the iodomethyl
derivative. [Martin et al. HCA 38 2009 1955; JOC 21 1512 19561.
2-Chloro-3-methylindole (2-chloroskatole) [51206-73-61 M 165.6, m 114.5-115S0. Purified
by chromatography on silica gel in CH2C121pet ether (1:2), followed by recrystn from aqueous EtOH or aqueous
acetic acid. [Phillips and Cohen JACS 108 2023 19861.
4-Chloro-2-methylphenol [1570-64-51 M 142.6, m 49O. Purified by zone melting.
4-Chloro-3-methylphenol [59-50- 761 M 142.6, m 66O. Crystd from pet ether.
4-Chloro-2-methylphenoxyaceytic acid MCPA [94-74-61 M 200.6, m 113-117O, 120°, 122-
123O. It is insoluble in H20 (sol 0.55gL at ZOO), and recrystallises from C6H6 or chlorobenzene as plates.
The pKaZ0 in H20 is 3.62 (3.05) [Acta Chem Scand 6 993 19521. The S-benzylthiouronium salt has m 164-
165O, and the Cu2+ salt has m 247-249Odec [Armarego et al. Nature 183 1176 1959; UV: Duvaux and Grabe
Acta Chem Scand 4 806 1950; IR: Joberg Acta Chem Scand 4 798 19501.
Chloromethyl phenyl sulphide { 7205-91 -61 M 158.7, b 63"/0.lmm, 9S0/12rnm, 113-
11S0/20mm. Dissolve in CH2C12 or CCI4 and dry over CaCI2, or pass through a tube of CaC12 and
fractionally distil using a fractionating column. Harmful vapours. It gives the sulphone (b 1300/lmm and
m 53O from EtOH) on oxidation with permonophthalic acid. [A 563 54 64 19491.
N-(Chloromethy1)phthalimide [I 7564-64-61 M 195.6, m 131-13S0, 134-13S0, 136.5O.
Purified by recrystn from EtOAc or CCl4 [JACS 70 2822 1948; Bohme et al. B 92 1258 19591.
1-Chloro-2-methylpropane see isobutyl chloride.
2-Chloro-2-methylpropane see rerr-butyl chloride.
4-(Chloromethy1)pyridine hydrochloride [1822-51-11 M 164.0, m 160-163O, 170-175O, 172-
173O. Purified by recrystn from EtOH or EtOH-dry Et20. It melts between 171O and 175O and the clear melt
resolidifies on further heating at 190° and turns red to black at 280° but does not melt again. The picrutehydrochloride
(prepared in EtOH) has m 146-147O. The free base is an oil, [Mosher and Tessieri JACS 73
4925 19511.
2-Chloro-1-methylpyridinium iodide [14338-32-01 M 255.5, m 203-20S0, 205-206O(dec),
207O. Purified by dissolving in EtOH and adding dry Et20. The solid is washed with Me2CO and dried at
20°/0.35mm. Store in the dark. Attempted recrystn from Me2CO-EtOH-pet ether (b 40-60°) caused some
exchange of the C1 substituent by I. The picrate has m 106-107O, and the perchlorate has m 212-213O. [W
and solvolysis: Barlin and Benbow JCS Perk Trans 2 790 19741.
Chloromycetin see chloramphenicol.
Chloromycetin palmitate see chloramphenicol palmitate.
1-Chloronaphthalene [90-13-11 M 162.6, f.p. -2.3O, b 136-136S0/20mm, 259.3°/760mm, d
1.194, n 1.6326. Washed with dilute NaHC03, then dried with Na2S04 and fractionally distd under reduced
pressure. Alternatively, before distn, it was passed through a column of activated alumina, or dried with CaC12,
then distd from sodium. It can be further purified by fractional crystn by partial freezing or by crystn of its
picrate to constant melting point (132-133O) from EtOH, and recovering from the picrate.
2-Chloronaphthalene [91-58-71 M 162.6, m 61°, b 264-266O.
dried under vacuum.
Crystd from 25% EtOWwater and
1-Chloro-2 naphthol [633-99-81 M 178.6, m 70°. Cryst from pet ether. Acetate has m 42-43O.

Purification of Organic Chemicals 145
2-Chloro-l-naphthol [606-40-61 M 178.6, m 64-65O. Crystd from pet ether
4-Chloro-l-naphthol
chl orofonn.
[604-44-41 M 178.6, m 116-117O, 120-121O. Crystd from EtOH or
6-Chloronicotinic acid [5326-23-81 M 157.6, m 190-193O, 198-199O(dec). Purified by recrystn
from hot H20 and is sublimed in a vacuum. [Pechmann and Welsch B 17 2384 1884; Herz and Murty JOC 26
122 19611.
4-Chloro-2-nitroaniline [89-63-41 M 172.6, m 116-116.5O. Crystd from hot water or EtOHIwater
and dried for 1Oh at 600 under vacuum.
2-Chloro-4-nitrobenzamide [3011-89-0] M 200.6, m 172O. Crystd from EtOH.
2-Chloro-l-nitrobenzene [88-73-31 M 157.6, m 32.8-33.2O. Crystd from EtOH, MeOH or pentane
(charcoal).
3-Chloro-l-nitrobenzene [121-73-31 M 157.6, m 45.3-45.8O.
(charcoal), then pentane.
Crystd from MeOH or 95% EtOH
4-Chloro-l-nitrobenzene [100-00-5] M 157.6, m 80-83O, 83.5-84O, b 113°/8mm, 242O/atm,
d :00-5 1.2914. Crystd from 95% EtOH (charcoal) and sublimes in a vacuum. [Emmons JACS 76 3470
1954; Newman and Forres JACS 69 1221 19471.
4-Chloro-7-nitrobenzofurazane (7-chloro-4-nitrobenzoxadiazole) [ I01 99-89-01 M 199.6, m
96.5-97O, 97O, 99-looo. Wash the solid with H20 and recrystallise from aqueous EtOH (1:l) as pale
yellow needles. It sublimes in a vacuum [W, NMR: Bolton, Gosh and Katritzky JCS 1004 19661.
l-Chloronitroethane [625-47-81 M 109.5, b 37-3S0/20mm, n 1.4224, n25 1.4235. Dissolved in
alkali, extracted with ether (discarded), then the aqueous phase was acidified with hydroxylamine hydrochloride,
and the nitro compound fractionally distd under reduced pressure. [Pearson and Dillon JACS 75 2439 19531.
2-Chloro-3-nitropyridine [5470-18-81 M 158.5, m 100-103°, 101-102°, 103-104O
(sublimes). Forms needles from H20. Purified by continuous sublimation over a period of 2 weeks at 50-
6O0/0.lmm. It has a pKa20 in H20 of -2.6 [Barlin JCS 2150 19641. The N-oxide has m 99-100°(from
CH2C12-Et20). [Taylor and Driscoll JOC 25 1716 1960; Ochiai and Kaneko Chem Pharm Bull Japan 8 28
19601.
2-Chloro-5-nitropyridine [4548-45-21 M 158.5, m logo. Crystd from benzene or benzenelpet ether.
a-Chloro-3-nitrotoluene see 3-nitrobenzyl chloride.
l-Chloropentane see n-amyl chloride.
3-Chloroperbenzoic acid [937-14-41 M 172.6, m 92-94O(dec). Recrystd from CH2C12 [Traylor and
Mikztal JACS 109 2770 19871. Peracid of 99+% purity can be obtained by washing commercial 85% material
with phosphate buffer pH 7.5 and drying the residue under reduced pressure. Alternatively the peracid can be
freed from m-chlorobenzoic acid by dissolving 50a of benzene and washing with an aq soln buffered at pH 7.4
(NaH2POflaOH) (5 x 100ml). The organic layer was dried over MgS04 and carefully evaporated under
vacuum. Necessary care should be taken in case of EXPLOSION. The solid was recrystd twice from
CH2Cl~Et20 and stored at Oo in a plastic container as glass catalyses the decomposition of the peracid. The
acid is assayed iodometrically. [JOC 29 1976 1964; Bortolini et al. JOC 52 5093 19871.
2-Chlorophenol [95-57-81 M 128.6, m 8.8O, b 61-62°/10mm, 176O/atm. Passed at least twice
through a gas chromatograph column. Also purified by fractional distn. It has pKa 8.34 at 2 5O in water.

146 Purification of Organic Chemicals
3-Chlorophenol [108-43-01 M 128.6, m 33O, b 44.2O/lmm, 214OIatm. Could not be obtained
solid by crystn from pet ether. Punfied by distn under reduced pressure. It has pKa 9.06 at 15O in water.
4-Chlorophenol [106-48-91 M 128.6, m 43O, 100-lO1°/lOmm. Distd, then crystd from pet ether (b
40-60°) or hexane, and dried under vacuum over P2O5 at room temp. It has pKa 9.38 at 20° in water.
[Bernasconi and Paschalis JACS 108 2969 19861.
Chlorophenol Red [4430-20-01 M 423.3, hm,,573nm. Crystd from glacial acetic acid.
4-Chlorophenoxyacetic acid [122-88-31 M 186.6, m 157O,
a-4-Chlorophenoxypropionic acid [3307-39-91 M 200.6, m 116O,
B-4-Chlorophenoxypropionic acid [3284- 79-51 M 200.6, m 138O. Crystd from EtOH.
3-Chlorophenylacetic acid [1878-65-51 M 170.6, m 74O,
4-Chlorophenylacetic acid [1878-66-61 M 170.6, m 102-105O, 105O, 106O. Crystd from
EtOWwater, or as needles from C6H6 or H20 (charcoal). The pKa is 4.12. The acid chloride (prepared by
boiling with SOC12) has b 127-129O/15mm. [Dippy and Williams JCS 161 1934; Misra and Shukla JlCS 28
480 19511.
4-Chloro-1-phenylbutan-1-one 1939-52-61 M 182.7, m 19-20°, b 134-137°/5mm, d:' 1.149,
nho 1.55413. Fractionate several times using a short column. It can be recrystd from anhydrous pet ether at
-2OO as glistening white rosettes and filtered at Oo and dried in a vacuum desiccator over H2SO4. The
semicarbazone has m 136-137O. [JACS 46 1882 1924,51 1174 1929, Hart and Curtis JACS 79 931 1957.
1-(2-Chlorophenyl)-1-(4-chlorophenyl)-2,2-dichloroethane (Mitotane, op'-DDD) [53-19-01
M 320.1, m 75.8-76.8O, 76-78O. Purified by recrystallisation from pentane and from MeOH or EtOH.
It is sol in isooctane and CC14. [Hailer et a]. JACS 67 1600 19451.
3-(4-Chlorophenyl)-l,l-dimethylurea [150-68-51 M 198.7, m 171O. Crystd from MeOH.
2-Chlorophenyl diphenyl phosphate see Chapter 4.
4-Chloro-l,2-phenylenediamine [95-83-01 M 142.6, m 69-70O. Recrystd from pet. ether.
4-Chlorophenyl isocyanate [104-12-21 M 153.6, m 28-31°, 31-32O, 32O, 32S0, b 80.6-
80.9°/9.5mm, 115-117°/45mm. Purified by recrystn from pet ether (b 30-40°) or better by fractional
distn. TOXIC irritant.
4-Chlorophenyl isothiocyanate [2131-55-71 M 169.6, m 44O, 43-45O, 45O, 46O, 47O, b 110-
115°/4mm, 135-136°/24mm. Check the IR first. Slur with pet ether (b 30-60°) and decant the solvent.
Repeat 5 times. The combined extracts are evap under reduced press to give almost pure compound as a readily
crystallisable oil with a pleasant anise odour. It can be recrystd from the minimum vol of EtOH at 50° (do not
boil too long in case it reacts). It can be purified by vac distn. Irritant [Org Synrh Coll Voi V 223 19731.
4-Chlorophenyl 2-nitrobenzyl ether, M 263.7, m 69O,
4-Chlorophenyl4-nitrobenzyl ether [5442-44-41 M 263.7, m 102O. Crystd from EtOH.
9-Chloro-9-phenylxanthene [42506-03-61 M 292.8, m 105-106O. Possible impurity is 9-hydroxy-9-
phenylxanthene. If material contains a lot of the hydroxy product then boil log in CHCI, (5Oml) with redistd
acetyl chloride (lml) until liberation of HCI is complete. Evapn leaves the chlorophenylxanthene as the
hydrochloride which on heating with benzene loses HCl; and on adding pet ether prisms of
chlorophenylxanthene separate and contain 0.5mol of benzene. The benzene-free compound is obtained on
drying and melts to a colourless liquid. [A 370 142 19091. The 9-phenylxanthyl group is called pixyl.
[JCSCC 639 19781.

Purification of Organic Chemicals 147
Chlorophyll a [479-61-81 M 983.5, m 117-120°, 150-153O, 178-180O (sinters at -150°),
[a]? -262O (Me2CO). Forms green crystals from MezCO, Et20 + H20, Et20 + hexane + H20 or Et2O +
pentane + H20. It is sparingly soluble in MeOH and insol in pet ether. In alkaline soh it gives a blue-green
colour with deep red fluorescence. A very crude chlorophyll mixture has been purified by chromatography on
low melting polyethylene (MI 0.044; 'Dow' melting index MI

148 Purification of Organic Chemicals
6-Chloropurine [87-42-3 1 M 154.6, m 179O(dec). Crystd from water.
2-Chloropyridine [109-09-1] M 113.6, b 49.0°/7mm, d 1.20, n 1.5322.
several days, then distd from CaO under reduced pressure.
Dried with NaOH for
3-Chloropyridine 1626-60-81 M 113.6, b 148O, d 1.194, n 1.5304. Distd from KOH pellets.
4-Chloropyridine [626-61-91 M 113.6, b 85-86°/100mm, 147-148°/760mm. Dissolved in
distilled water and excess of 6M NaOH was added to give pH 12. The organic phase was separated and extracted
with four volumes of ethyl ether. The combined extracts were filtered through paper to remove water and the
solvent evaporated. The dark brown residual liquid was kept under high vacuum [Vaidya and Mathias JACS
108 5514 19861. It can be distd but readily darkens and is best kept as the hydrochloride [7379-35-31 M 150.1,
m 163-165O(dec).
2-Chloropyrimidine [1722-12-91 M 114.5, m 63-65O, 66O, b 91°/26mm. It has been recrystd from
C6H6, pet ether or a mixture of both. It sublimes at 50°/18mm and can be distd in a vacuum. [IR: Shoq and
Thompson JCS 168 1952; Boarland and McOmie JCS 1218 19-51].
Chloroquinol [615-67-81 M 144.5, m 106O. Crystd from CHC13 or toluene.
2-Chloroquinoline [612-62-41 M 163.6, m 34O, b 147-148°/15mm, d35 1.2351, n25 1.62923.
Purified by crystn of its picrate to constant melting point (123-124O) from benzene, regenerating the base and
distilling under vacuum [Cumper, Redford and Vogel JCS 1183 19621. 2-Chloroquinoline can be crystd from
EtOH. Its picrate has m 122O (from EtOH).
4-Chloroquinoline [611-35-81 M 163.6, m 29-32O, 31°, b 127O/15mm, 130°/15mm,
26l0/744mm. Possible impurities include the 2-isomer. Best purified by converting to the picrate (m 212-
213O dec) in EtOH and recryst from EtOH (where the picrate of the 2-chloroquinoline stays in soh) or EtOAc .
The picrate is decomposed with 5% aqueous NaOH, extracted in CHC13, washed with H20, dried (MgS04),
evapd and distd in a vacuum. It can be steam distd from slightly alkaline aqueous solns, the aqueous distillate is
extracted with EtzO, evaporated and distd. The distillate solidifies on cooling. [Bobranski B 71 578 19381.
8-Chloroquinoline [611-33-61 M 163.6, b 171-171.5°/24mm, d 1.2780, n 1.64403. Purified
by crystn of its ZnCl2 complex (m 228O) from aqueous EtOH.
4-Chlororesorcinol [95-88-51 M 144.6, m 105O. Crystd from boiling CCl4 (log& charcoal) and air
dned.
5-Chlorosalicaldehyde [635-93-81 M 156.6, m 98.5-99O. Steam distd, then crystd from aq EtOH.
N-Chlorosuccinimide [128-09-61 M 133.5, m 149-150°. Rapidly crystd from benzene, or glacial
acetic acid and washed well with water then dried in YUCUO. [Phillips and Cohen JACS 108 2023 19861.
8-Chlorotheophylline [85-18-71 M 214.6, m 311°(dec). Crystd from water.
4-Chlorothiophenol
JOC 52 1720 198n.
ct-Chlorotoluene
[106-54-71 M 144.6, m 51-52O. Recrystd from aqueous EtOH [D'Sousa et al.
see benzyl chloride.
2-Chlorotoluene [95-49-81 M 126.6, b 159O, d 1.083, n 1.5255. Dried for several days with
CaC12, then distd from Na using a glass helices-packed column.
4-Chlorotoluene [106-43-41 M 126.6, f.p. 7.2O, b 162.4O, d 1.07, n 1.5208. Dried with BaO,
fractionally distd, then fractionally crystd by partial freezing.

Purification of Organic Chemicals 149
2-Chlorotriethylamine hydrochloride [869-24-91 M 172.1, m 208-210°.
MeOH (to remove highly coloured impurities).
Crystd from absolute
Chlorotrifluoroethylene [79-38-91 M 116.5, b -26 to -24O. Scrubbed with 10% KOH soln, then
10% H2SO4 soln to remove inhibitors, and dried. Passed through silica gel.
Chlorotrifluoromethane [75-72-91 M 104.5, m -MOO, b -81.5O. Main impurities were C02, 02,
and N2. The C02 was removed by passage through saturated aqueous KOH, followed by conc H2SO4. The 0 2
was removed using a tower packed with activated copper on kieselguhr at 2W0, and the gas dried over P205.
Chlorotriphenylrnethane [76-83-51 M 278.8, m 112-113O. Crystd from benzene soln (100ml)
containing a little acetyl chloride, by addition of 200ml of pet ether and cooling. Alternatively, a soln in ethyl
ether was saturated with dry HCl (by dripping conc HCl into conc H2SO4 and passing the gas through P205
towers) at Oo, then cooled in a Dry-ice/acetone bath. The crystals so obtained were recrystd from pet ether (b 30-
60°) using Dry-ice/acetone baths [Thomas and Rochow JACS 79 1843 1957.
5-Chlorouracil (5-chloro-2,4(6)-dihydroxypyrimidine) [1820-81 -11 M 146.5, m 314-418O
dec, 324-325O dec. Recrystallised from hot H20 (4g/500ml) using charcoal. It has pKa25 7.95 (7.90) and
>13 in H20. [McOmie et al. JCS 3478 1955; West and Barrett JACS 76 3146 19541.
4 - C h 1 o ro - 3,5 - x y 1 e no1 see 4 - C h 1 or o - 3,5 -dime t h y 1 p he n 01.
Cholamine chloride hydrochloride see (2-aminoethy1)trimethylammonium
hydrochloride.
chloride
5-P-Cholanic acid [546-18-91 M 360.6, m 164-165O, [a]: +21.7O (CHC13). Crystd from EtOH.
Cholanthrene 1479-23-21 M 254.3, m 173O. Crystd from benzene/ethyl ether.
Cholestane [481-21-01 M 372.7, m 80°, +29S0 (c 2, CHC13). Crystd from ethyl
ether/EtOH.
5a-Cholestan-30-01 [80-97-71 M 388.7, m 142-143°(monohydrate), +28O (c 1,
CHCl3), [a]~ +27.4O (in CHC13). Crystd from EtOH or slightly aqueous EtOH. [Mizutani and Whitten
JACS 107 3621 19851.
2-Cholestene [102850-21-5] M 370.6, m 75-76O, [01]2D4 +64O. Recrystd from MeOH or ethyl
ethedacetone. [Berzbrester and Chandran JACS 109 174 1987.
Cholesterol (57-88-51 M 386.7, m 148.9-149.4O, [ a ]-35O ~ ~ (hexane). ~ Crystd from ethyl
acetate, EtOH or isopropyl ether/MeOH. [Hiromitsu and Kevan JACS 1094501 1987. For extensive details
of purification through the dibromide, see Fieser [JACS 75 5421 19531 and Schwenk and Werthessen [Arch
Biochem Biophys 40 334 19521, and by repeated crystn from acetic acid, see Fieser [JACS 75 4395 19531.
Cholesteryl acetate [604-35-31 M 428.7, m 112-115O, [a]?$6
n-pentanol.
-51O (c 5, CHC13).
Crystd from
Cholesteryl myristate [1989-52-21 M 597.0. Crystd from n-pentanol. Purified by column
chromatography with MeOH and evaporated to dryness. Dissolved in water and ppted with HCl (spot 1) or
passed through a cation-exchange column (spot 2). Finally, dried in vacuum over P205. [Malanik and Malat
Anal Chim Acta 76 464 19751.
Cholesteryl oleate [303-43-5 1 M 651.1, m 48.8-49.4O.
Purified by chromatography on silica gel.

150 Purification of Organic Chemicals
Cholic acid [81-25-41 M 408.6, m 198-200°, [a1546 +41° (c 0.6, EtOH).
Dried under vacuum at 94O.
Crystd from EtOH.
Choline chloride [67-48-11 M 139.6. Extremely deliquescent. Purity checked by AgN03 titration or by
titration of free base after passage through an anion-exchange column. Crystd from absolute EtOH, or EtOHethyl
ether, dried under vacuum and stored in a vacuum desiccator over P2O5 or Mg(ClO&.
540nm, E 7.80 x lo4 (10M HCI). Crude material
(40g) is dissolved in water (25Oml) and filtered. Then added conc HCI (50ml) to filtrate, with stirring. Ppte is
filtered off, washed with HCl (2M) and dried. Redissolved in water (25Oml) and pptn repeated twice more in
water bath at 70°. Then dned under vacuum over solid KOH (first) then P2O5 [Martynov et al. Zh Analit Khim
32 519 19771.
Chromazurol S [1667-99-81 M 539.3, A ,
4-Chromanone [491-37-21 M 148.2, m 35-37O, 38S0, 39O, 41°, b 92-93O/3mm, 130-
132°/15mm, 160°/50mm. It has been recryst from pet ether, or purified by dissolving in C6H6 washing
with H20, drying (MgSOd), evaporate and dist in a vacuum, then recryst the residue. The liquid has a pleasant
lemon-like odour. The semicarbutone has m 227O. [Loudon and Razdan JCS 4299 19541. The oxime is
prepared from 3g of chromanone, 3g NH20H.HCI in EtOH (5Oml), 6g K2C03 and refluxed on a water bath for
6h. The soh is poured into HzO, the solid is filtered off, dried and dissolved in hot C6H6 which on addition of
pet ether yields the oxime as glisteneing needles m 140O. Decomposition of this gives very pure chromanone.
The benzal derivative is prepared from 3g of chromanone, 4g PhCHO in 50ml EtOH, heated to boiling, lOml
of conc HCI are added dropwise and set aside for several days. The derivative separates and is recrystd from EtOH
to give yellow needles, m 112O [JACS 45 2711 19231. Reaction with Pb(OAc)4 yields the 3-acetoxy
derivative m 74O (from pet ether + trace of EtOAc, [Cavil] et al. JCS 4573 19541.
Chromotropic acid [148-25-41 M 120.3. Crystd from water by addition of EtOH.
Chrysene [218-01-91 M 228.3, m 255-256O. Purified by chromatography on alumina from pet ether in
a darkened room. Its soh in C6H6 was passed through a column of decolorizing charcoal, then crystd by
concentration of the eluate. Also purified by crystn from C6H6 or CgH6-pet ether , and by zone refining.
[Gorman et a]. JACS 107 4404 19851. It was freed from 5H-benzo[b]carbazole by dissolving in N,Ndimethylformamide
and successively adding small portions of alkali and iodomethane until the fluorescent colour
of the carbazole anion no longer appeared when alkali was added. The chrysene (and alkylated 5Hbenzo[b]carbazole)
separated on addition of water. Final purification was by crystn from ethylcyclohexane and
from 2-methoxyethanol [Bender, Sawicki and Wilson AC 36 101 1 19641. It can be sublimed in a vacuum.
Chrysoidine G (4-phenylazo-1,3-benzenediamine monohydrochloride) [532-82-11 M 248.7, m
118-118.5O. Red-brown powder which is recrystd from H20. It gives a yellow soln in conc H2SO4 which
turns orange on dilution. Its solubility at 15O is 5.5% (H20), 4.75% (EtOH), 6.0% (cellosolve), 9.5%
(ethylene glycol), 0.005% (xylene) and insol in C6H6. The hydroiodide has m 184O (from EtOH) and the
picrate forms red needles m 196O. It has pKa values of 3.32 and 5.21 in H20. [Bull Chem SOC Japan 31 864
1958; B 10 213 18771.
Cinchonidine [485-71-21 M 294.4, m 210S0, -127.5O (c 0.5, EtOH). Crystd from
aqueous EtOH.
Cinchonine [118-10-5] M 294.4, m 265O,
ether.
+268O (c 0.5, EtOH). Crystd from EtOH or ethyl
Cincophen see 2-phenyl-4-quinolinecarboxylic acid.
1,8-Cineole [478-82-61 M 154.2, f.p. 1.3O, b 176.0°, d 0.9251. Purified by dilution with an equal
volume of pet ether, then saturation with dry HBr. The ppte was filtered off, washed with small portions of pet
ether, and then cineole was regenerated by stimng the crystals with water. It can also be purified through its o-
cresol or resorcinol addition compounds. Stored with sodium until required.

Purification of Organic Chemicals 151
trans-Cinnamaldehyde
[14271-10-91 M 132.2, m -4O, -7S0, -9O, b 80°/0.4mm,
85.8O/l. lmm, 125-128O/l lmm, 152.2°/40mm, 163.7°/60mm, 199.3°/200mm, 246O/7 60 m m
dec, di0 1.0510, nio 1.623. Purified by steam distn (sol 1 in 700 parts H20) followed by distn in vacuo.
The cis-isomer has b 67-69°/40mm and d:' 1.0436 and 4' 1.5937. The trans-semicarbazone has m 210° dec
from CHC13-MeOH (cis-semicarbazone has m 196O); the trans-phenylsemicarbazone has m 177O from CHC13-
MeOH (the cis-phenylsernicarbazone has m 146O); the trans-2,4-dinitrophenylhydra~one has m 250° dec from
MeOH as the cis-isomer [Gamboni et al. HCA 38 255 1955; Peine B 17 2117 1884; JOC 26 4814 1961;
JACS 86 198 19641.
trans-Cinnamic acid [140-10-31 M 148.2, m 134.5-135O. Crystd from benzene, CCl4, hot water,
water/EtOH (3: l), or 20% aqueous EtOH. Dried at 600 under vacuum.
Cinnamic anhydride [538-56-71 M 278.4, m 136O. Crystd from benzene or toluene/pet ether (b 60-
80O).
N-Cinnamoyl-N-phenylhydroxylamine [7369-44-01 M 239.3, m 158-163O. Recrystd from EtOH.
Cinnamyl alcohol [104-54-1
cm-l). Crystd from ethyl ethedpentane.
J M 134.2, m 3 3O, b 143S0/14mm, A, 251nm (E 18,180M-I
Cinnoline [253-66-71 M 130.2, m 38O.
at Oo.
Crystd from pet ether. Kept under N2 in sealed tubes in the dark
Citraconic acid [498-23-71 M 130.1, m 91O. Steam distd and crystd from EtOWligroin.
Citraconic anhydride [616-02-41 M 112.1, m 8-9O, b 47°/0.03mm, 213°/760mm, di0 1.245,
nio 1.472. Possible contamination is from the acid formed by hydrolysis. If the IR has OH bands then reflux
with Ac2O for 30 min, evaporate then distil the residue in a vacuum; otherwise distil in a vacuum. Store in a
dry atmosphere. [BJ 191 269 19801.
Citranaxanthin [3604-90-81 M 456.7, m 155-156O, &llTm 410 (349nm), 275 (466nm) in
hexane. Purified by chromatography on a column of 1 : 1 magnesia-HyfloSuperceI. Crystd from pet ether.
Stored in the dark, under inert atmosphere, at Oo.
Citrazinic acid (2,6-dihydroxyisonicotinic acid) [99-11-61 M 155.1, m >300°. Yellow powder
with a greenish shade, but is white when ultra pure and turns blue on long standing. It is insoluble in H20 but
slightly soluble in hot HCI and soluble in alkali or carbonate solutions. Purified by precipitation from alkaline
solutions with dilute HCI, and dry in a vacuum over P2O5. Its pKa values in H20 are 3.00 and 4.76. The ethyl
ester has m 232O (evacuated tube) and a pKa of 4.8 1 in MeOCH2CH20H [IR: Pitha Coll Czech Chem Comm
28 1408 19631.
Citric acid (H20) [5949-29-11 M 210.1, m 156-157O. 153O (anhyd). Crystd from water.
Citronella1 (3,7-dimethyloctan-6-al) [(+): 2385-77-51 [(-): 5949-05-31 M 154.3, b 67°/4mm,
89°/14mm, 104-105°/21mm, 207°/760mm, f20°, [a]V+16So (neat). Fractionally distd.
Alternatively extracted with NaHS03 solution, washed with Et20 then acidified to decompose the bisulphite
adduct and extracted with Et20, dried (Na2S04), evaporated and distd. Check for purity by hydroxylamine
titration. The RD in MeOH (c 0.167) is: [a],,, +9O, [a1589 +1l0, [a1275 +12O and [a1260 12O. The
semicarbazone has m 85O, and the 2,4-dinitrophenylhydrazone has m 79-80°. [IR: JCS 3457 1950; ORD:
Djerassi and Krakower JACS 81 237 19591.
P-Citronellene (2,6-dimethylocta-2,7-diene) [S-( +): 2436-90-01 [R-(-): 10281 -56-81 M 138.3, b
153-154°/730mm, 15S0/atm, di20.7566, n?,' 1.43070, [a];!6 +13O, [a];!6 *loo (neat).
Purified by distillation over Na three times and fractionation. [(-) Arigoni and Jeager HCA 37 881 12954; (+)
Eschenmoser and Schinz HCA 33 171 19501.
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