Trans-cis isomerization of 4-(2-(9-anthryl)vinyl)pyridine. Molecular structures and 1H NMR kinetic studies

Abstract

Both cis- and trans-isomers of 4-(2-(9-anthryl)vinyl)pyridine were isolated and their molecular structures established by X-ray crystallographic method. Variable temperature 1H NMR spectroscopy was used to study the trans to cis isomerization of the title compound. The kinetic study of the reaction was based on the ratio of the NMR integration heights in toluene-d8 of the double doublet due to the cis-isomer at δ 8.51 to that of the multiplet at δ 8. 15 which was kept constant during the whole experiment. The isomerization process was found to be first order and the Arrhenius activation parameters Ea , In A , Δ H≠ and Δ S≠ were calculated as 27.84 kJ/mol, 6.71, 25.23 kJ/mol and - 197.89 J/(K·mol), respectively. Besides, conformational analyses of both compounds based on molecular modelling were carried out and the results were used to compare with the experimental data.