Substituent effects on the formation of benzyl ions from ortho-methoxy substituted 1,1-diarylalkanes under electron ionization: correlations between the abundance of the process and the 13C-NMR chemical shifts of the neutral precursors

Abstract

Good linear relationships have been obtained between the abundance of the formation process of benzyl ions from ortho-methoxy-substituted 1,1-diarylalkanes, through consecutive rearrangement reactions induced by electron ionization, and 13 C-NMR chemical shift values of C-1 of the ortho-methoxy-substituted aromatic ring of the neutral precursors for a large number of compounds: 1,1-diphenylethanes 1-19, 2-methyl-1,1-diphenylpropanes 20-37, and 1,1,1-trichloro-2,2-diphenylethanes 38-44. This result is satisfying as good linear relationships between the ion abundances in the mass spectrum and the substituent effects are not easily obtained. Further, the abundance of the process depends on the effects of substituents linked to the ortho-methoxy-substituted benzene ring (ring A) while measurable effects of substituents linked to the other benzene ring (ring B) have not been observed.