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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.
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