Substituent effects in the base-catalysed isomerizations of arylpropenes with ethoxide; the reaction of some aryl-substituted propenes with sodium ethoxide at 81 °C

Abstract

The reactions of 3-phenylprop-1-ene and its p-methyl, m-chloro-, p-chloro-, and m- and p-bromo-derivatives, with sodium ethoxide in ethanol have been investigated at 81 °C. It was found that the effect of substituents on the rate of isomerization of these compounds to the corresponding 1-arylprop-1-enes follow the order p-Cl > m-Br ∼m-Cl > H > p-Me. The results are consistent with the view that the rearrangement occurs through the BS_E1′ mechanism. The reaction of 3-(p-bromophenyl)-1-ene is complicated by the incursion of the reaction leading to nucleophilic displacement of bromine by ethoxide.