SOLVENT EFFECT IN PERICYCLIC-REACTIONS .10. THE CHELETROPIC REACTION

The effect of the solvent on the cheletropic reaction of 3,4-dimethyl- 2,5-dihydrothiophen-1,1-dioxide was kinetically investigated in 14 sol vents. The rate constants of the forward reaction as well as those of the reverse process and the corresponding equilibrium constants were f ound to be linearly correlated with the E(T)(30) solvent polarity para meter. The solvent effect on be interpreted in terms of change of pola rity during the activation process. The different response of the forw ard and reverse process to the increase of solvent polarity pointed ou t a clear difference between pericyclic reactions characterized by non -specific solvent effects and those whose medium effect is determined by the specific interaction between the FMO of solute and solvent. (C) 1996 Elsevier Science Ltd.