UV AND PMR SPECTRA OF 10 RELATED DIARYL CARBONIUM IONS

We have prepared the following cations, and characterised their u.v. and PMR spectra: diphenyl-, phenyl-(2-methylphenyl)-, phenyl-(2-ethylphenyl)-methyl; 1,1-diphenyl-, 1-phenyl-1-(2'-methylphenyl)-, 1-phenyl-1-(2'-ethylphenyl)-, 1-phenyl-1-(4'-ethylphenyl)-ethyl; 1,1-diphenyl-n-butyl; 1-phenylindanyl; 3-methyl-1-phenylindanyl. All ions have two absorption peaks in the u.v. region and the most meaningful correlations and trends are found in terms of the total oscillator strengthf{hook}t = f{hook}s + f{hook}l (s, short; l, long wavelength) and of the ratio f{hook}s f{hook}l. the different degrees of deshielding found in the pmr spectra (compared to those of the corresponding carbinols) give information on the charge distribution in the ions. There is a linear correlation between log δτ (δτ = downfield shift) and the number of bonds separating a hydrogen atom from the charged carbon atom. Both u.v. and pmr spectra show the profound changes brought about when a 1,1-diarylethyl ion is cyclised to the corresponding indanyl ion. © 1969.