Half-Esterification of a Diol

The general procedures for the preparations of half-esters of diols are not usually very efficient in that both unreacted diol and diester are present along with the desired half-ester. Unfortunately, the present example is no exception but is included as an illustration of the type of results that can be expected under these circumstances. The diol employed for this reaction is prepared in Chapter 5, Section II. 

In a 250-ml three-necked flask fitted with a magnetic stirrer, a pressure-equalizing dropping funnel, and a thermometer is placed a solution of l,4-cyclohexanediol(l 1.4g, 0.10 mole), 35 ml of chloroform, and 27 ml of dry pyridine. The solution is cooled in an ice bath to 0-5 and is maintained below 5 throughout the addition. A solution of benzoyl chloride (14 g, 0.10 mole) in 30 ml of dry chloroform is added with stirring at a rate so as to keep the temperature below 5° (approx. 40 minutes). After completion of the addition, the mixture is allowed to come to room temperature and stand overnight. The chloroform solution is washed four times with 50-mI portions of water, once with 50 ml of 5 % sulfuric acid solution, and finally with saturated sodium chloride solution. The chloroform solution is then dried (sodium sulfate), and the solvent is removed. Fractionation of the residue gives a cis and trans mixture of 4-benzoyloxycyclohexanol, bp 175-17870.2 mm, as a very viscous oil, yield about 55%. 

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