Chloroalkanes alcohol conversion

No systematic studies of a number of compoimds have yet appeared to discover correlations suggestive of mechanism. This paper presents the fractional conversions and reaction rates measured under reference conditions (50 mg contaminants/m ) in air at 7% relative humidity (1000 mg/m H2O), for 18 compounds including representatives of the important contaminant classes of alcohols, ethers, alkanes, chloroethenes, chloroalkanes, and aromatics. Plots of these conversions and rates vs. hydroxyl radical and chlorine radical rate constants, vs. the reactant coverage (dark conditions), and vs. the product of rate constant times coverage are constructed to discern which of the proposed mechanistic suggestions appear dominant. 

Selected examples of the conversion of alcohols into chloroalkanes... 

Chloroalkanes.1 The conversion of primary alcohols to 1-chloroalkanes with aqueous hydrochloric acid is not useful because of mediocre yields (30-60%). The rate and yield of this reaction are improved considerably by use of a surfactant such as cetyltrimethylammonium bromide or cetylpyridinium bromide. 

Use thionyl chloride, SOC12, for the alcohol to chloroalkane conversion. Using thionyl chloride with secondary alcohols shifts the mechanism from SN1 to SN2 and, therefore, removes carbocation formation from the process. No carbocation, less risk of rearrangement. 

The most widely used reagent for the conversion of primary and secondary alcohols to chloroalkanes is thionyl chloride, SOCI2. Yields are high, and rearrangements are seldom observed. The by-products of this conversion are HCl and SO2. 

The mechanism for the reaction of thionyl chloride with a carboxylic acid to form an acid chloride is similar to that presented in Section 10.5C for the conversion of an alcohol to a chloroalkane and involves initial chlorosulfite formation, followed by nucleophilic attack of chloride ion on the carbonyl carbon to give a tetrahedral carbonyl addition intermediate, which decomposes to give the acid chloride, SO2, and chloride ion. 

The advantages of the partial chlorination of alcohols (60-95% conversion) with HCl and completion of the chlorination by a catalytic phosgenation and subsequent decarboxylation of the resulting chloroformates have been combined in a two-stage process [974, 982]. Only small amounts of dialkyl ethers, alkenes, isomeric chloroalkanes, or dialkyl carbonates are claimed to be formed as side products. 

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