1H nuclear magnetic resonance study of the kinetics of the reaction of N,N-dialkylformamide dimethyl acetals with secondary amines

Abstract

Rate constants and activation parameters (ΔG^≠, ΔH^≠, ΔS^≠) for the reactions of N,N-dialkylformamide dimethyl acetals with four secondary amines have been estimated by ¹H n.m.r. spectroscopy. The reactions are reversible and obey a second-order kinetic equation. Substitution of one methoxy group of the amide acetal by the amine entity is found to give ester aminals which are subject to decomposition (ΔG^≠ 92–103 kJ mol^–1). A transamination reaction yields a new amide acetal at higher temperatures (ΔG^≠ 115 kJ mol^–1). On the basis of the kinetic data, the mechanism of these reactions is discussed.