Abstract
Pyrolytic conversion of S-(2-alkenyl) S-alkyl dithiocarbonates (allylic dithiolcarbonates) to 2-alkenyl alkyl sulfides (allylic sulfides) was catalyzed by phenols bearing electron-attracting substituents. The reaction is pseudo-first-order and the apparent first-order rate constants are proportional not only to the concentration of phenols but also to the hydrogen-bonding capability of phenols. The entropy of activation for the phenol-catalyzed reaction is ca. 8 e.u. smaller than that for the uncatalyzed reaction. The reactivity of S-(1-phenylallyl) S-alkyl dithiocarbonates did not obey Hammett's or Taft's equation. Based on these findings together with the MNDO (modified neglect of diatomic overlap) calculation data, a possible role of phenols in the pyrolytic conversion of allylic dithiolcarbonates to allylic sulfides is discussed.
