Detropylations of N,N-dimethyltropylamine and N-tropylacetamide

Abstract

Rates have been measured for the decomposition of N-tropylacetamide, 1, in aqueous acid yielding acetamide and tropylium, and for its formation from tropylium and acetamide in aqueous solution. Reaction of 1 in dilute hydrochloric acid has k_H⁺= 2.49 × 10^–2 dm³ mol^–1 s^–1 at 25 °C, and the equilibrium constant for its formation from tropylium tetrafluoroborate and acetamide is 8.4 × 10^–3. In trichloroacetic and dichloroacetic acid buffers, rates show dependence on buffer concentration. A mechanism for the transformation is proposed, with N-protonated 1 as a transition state or high energy intermediate. Decomposition of N,N-dimethyltropylamine in aqueous acid solution at PH < 3.5 shows good first-order behaviour, k= 4.58 × 10^–1 s^–1 at 25 °C, with no dependence on acid concentration or on ionic strength.