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.
在具有电子吸引取代基的
酚类催化下,S-(2-烯基)S-烷基二
硫代
碳酸盐(烯丙基二
硫代
碳酸盐)发生热解转化,生成2-烯基烷基
硫化物(烯丙基
硫化物)。反应呈现伪一级动力学特征,表观一级速率常数不仅与
酚类浓度成正比,还与
酚类的氢键形成能力成正比。与非催化反应相比,
酚类催化反应的活化熵减少了约8熵单位。S-(1-苯基烯丙基)S-烷基二
硫代
碳酸盐的反应活性不遵循Hammett或Taft方程。结合MNDO(修正的双原子重叠忽略)计算数据,基于这些发现,讨论了
酚类在烯丙基二
硫代
碳酸盐热解转化为烯丙基
硫化物过程中的可能作用。