Chlorides from alcohols

Alkyl chlorides from alcohols and chlo-rovinylamines, 41, 23 5 - A1 k y 1 -1,2,3,4,5-p c n tachlorocy clopcn -tadienes from hexachlorocydo-pentadiene and trialkyl phosphites, 43, 90 AlleNE, 43,12... 

Carbon tetrachloride-organo-phosphine, chlorides from alcohols with, 54, 63 CARBONYL CYANIDE, 51, 70 Carbonyl cyanide, with alcohols, 51, 72... 

Alkyl chlorides, from alcohols, benzyl chloride, and triphenyl phosphite,... 

Another method that provides chlorides from alcohols with retention of configuration involves conversion to a xanthate ester, followed by reaction with sulfuryl chloride. This method is thought to involve collapse of a chlorinated adduct of the xanthate ester. The reaction is useful for secondary alcohols, including stoically hindered structures.8... 

Although detailed mechanisms have not been established, the first step is thought to be formation of an unstable mixed anhydride, which then extrudes S02 and collapses with attack of chloride at the carbonyl carbon. A similar mechanism occurs in the formation of alkyl chlorides from alcohols and thionyl chloride (Section 15-5A) ... 

For the preparation of bromides and chlorides from alcohols, the corresponding acids, HBr and HC1, are the reagents of choice (32). The mechanism (33) for this reaction is believed to involve a protonated intermediate (Reaction XXIV) which is further attacked by the halide. 

Chloride, from alcoholic solution of acetate by alcoholic calcium chloride separates from alcohol or benzene in felted masses of needles, M.pt. 183 C. Bromide, forms larger crystals than the chloride and is more soluble M.pt. 182 C. Iodide, much more soluble, M.pt. 169 C. Thiocyanate, fine white, gritty crystals, M.pt. 135 C., decomposing at 140° C. Hydroxide, from alcoholic acetate and the requisite amount of sodium hydroxide in alcohol, forms hard, warty masses of crystals, M.pt. 162° C. Formate, fine felted needles, M.pt. 145° C., decomposing at 150° C. 

Thionyl chloride is the classical reagent for the preparation of alkyl chlorides from alcohols with retention of configuration. This reaction is known to proceed via alkyl chlorosulfinates (7 75) which decompose by an ion pair mechanism, but may be diverted to an SN2 displacement path by addition of pyridine171 Wagner-Meerwein rearrangements have been observed in the course of alkylchlorosulfinate decomposition, e.g. (176) - (777)172). The behavior of the isomeric chlorosulfinates (178) and (179) is consistent with competitive ion pair collapse and 1,2-alkyl shift173. ... 

Without additional reagents Chlorides from alcohols s. 1,421 4,497 w.a.r. OH —Cl... 

A rapid method of preparing alkyl chlorides from alcohols on a laboratory scale consists in reaction with benzoyl chloride in the presence of dimethyl-formamide. During the exothermic reaction lower alkyl chlorides distil off spontaneously and can be purified by subsequent fractionation. 

Alkyl halides. The Vilsmeier reagent has been used to a limited extent to replace an hydroxyl group by chlorine. Actually (1) is a useful reagent for preparation of alkyl chlorides from alcohols without rearrangement. The reaction is conducted at 75-100° in dioxane, DMF, CH3CN, or HMPT. The replacement occurs with inversion. Yields are usually in the range 75-85%. 

Alkyl Chlorides. iV,iV-Diphenylformamide is reported to be an improvement on DMF when used with oxalyl chloride to prepare primary and secondary alkyl chlorides from alcohols. ... 

Methyllithiumflithium chloride tosyI chloride Chlorides from alcohols s. 24, 840... 

Sodium hydroxide chloroform Chlorides from alcohols under basic conditions... 

Prim, chlorides from alcohols CHgOH CHgCl... 

Chlorides from alcohols via xanthates Retention of configuration... 

Selenium dioxide j trimethylsilyl chloride Chlorides from alcohols... 

The mechanism is similar to that for the formation of chlorides from alcohols and thionyl chloride. The hydroxyl group is converted to a good leaving group by thionyl chloride, followed by a nucleophilic acyl substitution in which chloride is the nucleophile (compare with Sec. 7.10). Phosphorus pentachloride and other reagents can also be used to prepare acyl chlorides from carboxylic acids. 

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