Dimethyl sulfoxide as a solvent in the Williamson ether synthesis

Abstract

Using the conventional Williamson ether synthesis, n-butyl ether was prepared from sodium hydroxide, n-butyl alcohol, and n-butyl chloride using excess of the alcohol as solvent in 61% yield after 14 h reaction time. However, when the excess alcohol was replaced by dimethyl sulfoxide, the yield of ether rose to 95% with 9.5 h reaction time. Other primary alkyl chlorides exhibited similar behavior to n-butyl chloride, but secondary alkyl chlorides and primary alkyl bromides gave little etherification, elimination being the major reaction. Unreactive halides, such as vinyl chloride, phenyl bromide, and 2,4-dinitrobromobenzene, were not etherified in dimethyl sulfoxide. The reaction products obtained from aliphatic dichlorides depended upon the relative positions of the chlorine atoms. Secondary alcohols reacted to give ethers, but tertiary alcohols were very unreactive. Polyols generally gave high yields of ethers, the major product being that in which all but one of the hydroxyl groups became etherified. Under forcing conditions, however, completely etherified polyols could be obtained.