PROPORTION OF 1,3-PHENYL MIGRATION IN TRIFLUOROETHANOLYSIS, METHANOLYSIS, AND HYDROLYSIS OF (ME3SI)2C(SIME2PH)(SIET2I)

Solvolysis of the iodide (Me3Si)2C(SiMe2Ph)(SiEt2I), 2, in CF3CH2OH-CCl4 has been shown to give the rearranged and unrearranged products, (Me3Si)2C(SiEt2Ph)(SiMe2OCH2CF3) and (Me2Si)2C(SiMe2Ph)(SiEt2OCH2CF3), respectively, in ca. 85:15 ratio. Reaction of 2 with MeOH-CCl4 gives the rearranged and unrearranged methoxides in ca. 75:25 ratio in the presence of Ag2SO4 (which promotes the formation of a Ph-bridged cation) and ca. 65:35 in its absence. In contrast, reaction with water-dioxane gives the rearranged and unrearranged hydroxides in only ca. 20:80 ratio, but the ratio becomes ca. 60:40 if Ag2SO4 is present. The results provide confirmation of the view reached previously, on the basis of the effects of the substituents Y on the rates of solvolyses of the compounds (Me3Si)2C(SiMe2C6H4Y)(SiMe2I), that the parent compound (Y = H) undergoes trifluoroethanolysis exclusively by an S(N)1 process (involving rate-determining formation of a phenyl-bridged cation), hydrolysis very predominantly by an S(N)2 process but with a small S(N)1 contribution, and methanolysis by a mixture of S(N)1 and S(N)2 processes with the former slightly predominating.