Kinetics of formation of substituted styrene oxides by reaction of 2-aryl- and 1-aryl-2-halogenoethanols with aqueous alkali

Abstract

The kinetics of formation of m- and p-substituted styrene oxides by reaction of 1- and 2-aryl-2-halogenoethanols with aqueous alkali have been interpreted according to the Winstein–Lucas mechanism. The respective Hammett ρ values for overall reaction of 1- and 2-aryl-2-halogenoethanols are 0·32 and –1·13. The effects of substituents on the pre-equilibria have been estimated and it is concluded that the ρ values for the respective cyclizations are –0·34 and –1·61. The relative rates of dehalogenation of 2-halogeno-2-phenylethanols (k_Cl:k_Br:k_I= 0·035: 1·3:1) have been contrasted with those for other systems. The effect of phenyl substitution on the rate of formation of three-membered rings is discussed.