Nucleophilic attacks on carbon–carbon double bonds. Part X. Nucleophile-catalysed cis–trans isomerisation of cis-4-nitrochalcone and of diethyl maleate in 95% ethanol

Abstract

The catalytic cis–trans isomerisation of 4-nitrochalcone and of diethyl maleate in the presence of various nucleophiles has been studied spectrophotometrically in 95% ethanol. The reactivity order was: OH^– > piperidine > N₃ ^– > BuⁿNH₂ > C₆H₁₁·NH₂, benzylamine > Prⁿ ₂NH > Pr¹ ₂ NH Buⁿ ₃N, C₅H₅N, Br^–. The isomerisation is of overall second order (first order in each the substrate and the nucleophil) at low nucleophile concentrations, but the second-order rate coefficients fall with increase in the catalyst concentration. The kinetic behaviour, mechanism and factors influencing the reaction are discussed.