The mode of scission ofcis- andtrans-3-methoxycyclohexene oxides by hydrogen chloride, hydrogen bromide, ammonia, acetic acid, and methanol (under both acidic and alkaline conditions) has been examined using vapor-phase chromatography to detect and isolate minor isomers. Approximately 10% of the product from opening of thetransoxide is formed by attack at position-2 with each of these nucleophiles, whereas opening of thecisoxide proceeds exclusively by attack at position-1. The results are interpreted as reflecting very similar transition states for all of these reactions, with differences in product distributions for the two oxides being governed by the inductive effect of the methoxyl group and by steric factors in the corresponding transition states.