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
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 > Prn2NH > Pr12 NH ⋙ Bun3N, 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.