Metastable ion study of organosilicon compounds. Part X. o-CH 3C 6H 4COOSi(CH 3) 3 and o-CF 3C 6H 4COOSi(CH 3) 3

Abstract

The unimolecular metastable ion dissociations of o-trimethylsilyl toluate, o-CH 3C 6H 4COOSi(CH 3) 3 (1) and its fluorine analogue, o-trimethylsilyl α, α, α-trifluorotoluate, o-CF 3C 6H 4COOSi(CH 3) 3 ( 2), upon electron impact, have been investigated by means of B/E linked scan and high resolution data. The fragmentation processes of these compounds were elucidated with the aid of those of the corresponding acids, o-toluic acid, o-CH 3C 6H 4COOH ( 3) and o- α, α, α-trifluorotoluic acid, o-CF 3C 6H 4COOH ( 4), respectively. No molecular ion is observed for 2, but a fairly abundant molecular ion is observed for 1. The fragmentation of 1 +· is different from that of 2 +·, except for the loss of −CH 3 from the respective molecular ions. In the case of 1, (CH 3) 3SiOH is eliminated from 1 +· with the migration of the hydrogen from the methyl group attached to the benzene ring to the ether oxygen, giving rise to the peak at m/ z 118. The corresponding loss was not observed in the fragmentation of 2 +·. This was attributable to a greater electronegativity of the fluorine atom than that of a hydrogen atom. In the fragmentations of the compounds studied here, the so-called ortho-effect is operative. During the fragmentation of 2 +· and 4 +·, interesting F atom rearrangements were observed.