PYROLYSIS OF 4-T-BUTYL-1-METHYLCYCLOHEXYLPHENYL SULFOXIDE

The pyrolysis of the two isomers in 4-t-butyl-1-methylcyclohexyl pheny l sulfoxide ( 1 ), one of which is that the phenylsulfinyl group on su bstrate ( 1 ) is sited in an axial position (E-form) and other is in a n equatorial position (Z-form), was investigated by comparing the reac tion rates in dioxane. As the pyrolytic products, the mixtures of two kinds of 4-t-butyl-1-methylcyclohexene (endo-olefin) and 4-t-butyl-1-m ethylenecyclohexane (exo-olefin) were obtained from the substrates. Th e formation ratio of olefin isomers, (exo/endo), of Z-form was about 1 /4 compared with that of E-form, while, the reaction rate of Z-form wa s about three times larger than that of E-form. The activation paramet ets were that E(a) is ca. 120 kJ.mol-1 both isomers E and Z, while DEL TAS considerably differed in both isomers as ca. -2 in E-form and ca. -15 JK-1 in Z-from, respectively. From these results, it was suggested that the faster reaction rate of Z-form than that of E-form was consi dered to be due to a repulsing action of a gamma-hydrogen in an axial position to the sulfur atom in the phenylsulfinyl group of cyclohexyl ring in the substrate ( 1 ), and further, a predominant formation of t he endo-olefin in the pyrolysis of Z-form than that of E-form could al so be explained by the above described action of the gamma-position hy drogen.