Thermal isomerization of stilbene and styrylpyridines in the liquid state

Abstract

The thermal isomerization of stilbene and 2-, 3-, and 4-styrylpyridines in the pure liquid state has been studied at various temperatures. Rate parameters for stilbene and 3-styrylpyridine indicate an isomerization mechanism via the singlet state, whereas for 2-styrylpyridine the triplet state seems to be involved. For 4-styrylpyridine, the upward curvature of the Arrhenius plot is explained as due to a change in the mechanism from singlet to triplet on going from higher to lower temperatures.