Reactivities of variously substituted 4-heteracyclohexanones in the formation of oximes

Abstract

The rates of oxime formation of 41 heterocyclic ketones have been measured at 5 °C in aqueous alcoholic solution buffered at pH 6.85. The data indicate an overall second-order reaction, first order each in ketone and hydroxylamine. In all cases investigated the reaction appears to be irreversible under the experimental conditions employed. Increased steric retardation is observed as steric crowding around the carbonyl function increases, suggesting that rate-determining attack of the hydroxylamine on the carbonyl group takes place. The rates of oxime formation for 4-piperidones, oxan-4-ones, thian-4-ones, the corresponding 1,1-dioxides, and selenan-4-ones differ significantly.