Activation parameters of an organotin-catalyzed alcohol-isocyanate reaction

In this paper, the kinetics of the reaction of phenylisocyanate with cyclop entanol, catalyzed by di(n-butyl)tin di-(2-ethylhexanoate) (DBTDEH), was st udied at different temperatures in the same solvents as previously [l], i.e in acetonitrile (ACN), di-(n-butyl)ether (DBE) and toluene (Tol), in order to determine the Arrhenius energy, which is shown to be larger in the pres ence of the tin(IV) catalyst than in its absence [2], and the apparent acti vation entropy, which was derived from the values of the extrapolated inter cepts of the In k - 1/T graphs. The results demonstrate that entropic confi gurational effects are the prevailing cause of the accelerating effect of t he tin(IV) catalyst on this reaction.