The mechanism of epoxide reactions. Part XII. Reactions of ethylene oxide with alcohols in the presence of sodium alkoxides and of tertiary amines

Abstract

The kinetics of the base-catalysed solvolyses of ethylene oxide in a series of alcohols have been studied and comparisons made between reactions catalysed by sodium alkoxides and reactions catalysed by tertiary amines. In the former case the reactions take place in a single step and the effects of substituent groups on reactivity tend to cancel, so that in the temperature range 60–70° the rates in nine alcohol–alkoxide combinations are all very similar.

The amine-catalysed reactions take place in several stages, the active catalyst in the case of triethylamine at temperatures below 50° being triethyl-2-hydroxyethylammonium alkoxide, formed by an initial relatively slow reaction between triethylamine and ethylene oxide and subsequent rapid equilibration of the resulting zwitterion with solvent. With a series of nuclear-substituted NN-dimethylanilines nucleophilic catalysis was also demonstrated and at higher temperatures this probably constitutes the major reaction route for reactions catalysed by tertiary amines. General base catalysis by tertiary amines was shown to be negligible in all the solvents studied.