EXPERIMENTAL AND THEORETICAL-STUDIES ON THE ISOMERIZATION OF ALLYL THIOCYANATE TO ALLYL ISOTHIOCYANATE

The mechanism of isomerization of allyl thiocyanate to allyl isothiocy anate has been investigated both experimentally and theoretically. The kinetic study indicates that the reaction is unimolecular and is not ionic. The entropy of activation suggests strongly that the mechanism involves a cyclic transition stare. The rate of reaction was retarded to a small extent in polar solvents relative to that in nonpolar solve nts. Ab initio MO calculations indicate, in agreement with the experim ental results, that the reaction proceeds through a cyclic transition state, one in which the SCN moiety is almost linear. Thus, this is a [ 3,3] sigmatropic rearrangement. The charge separation in. the transiti on state was substantial. The retardation of the reaction in polar sol vents was attributed to the difference in solvation in the original st ate and in the transition state. (C) 1997 John Wiley & Sons, Inc.