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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.
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