Electronic absorption spectra of some monosubstituted benzenes in the vapour phase

Abstract

The near u.v. absorption spectra in the vapour phase and in solution of phenyl methyl sulfone, phenyl methyl sulfonate, benzene sulfonylchloride, benzenesulfonamide, benzoyl chloride, benzoyl bromide, and benzoyl cyanide have been investigated. The various transitions observed are discussed in terms of the frequency shift with respect to benzene transitions, intensity data, solvent effect and vibrational analysis. It is concluded that the absorption at the lower frequency is the same type for all monosubstituted benzene derivatives and it is related to A 1 g → B 2 u transition in benzene. The main absorption of high intensity in the middle spectral region seems to be dominated by charge transfer structures between the benzene ring and the substituent, and thus the analogy with the benzene transition at 1980 A breaks down for strong substituents.