EFFECT OF SUBSTITUENTS IN THE RING ON THE STRUCTURE AND ELECTRON-DENSITY DISTRIBUTION IN BENZYL HALIDES

The results of calculations for benzyl chlorides and benzyl bromides t hat contain substituents in the ring by different quantum-chemical met hods are compared. The electron density on the benzyl carbon atom incr eases as the electron-withdrawing properties of substituents are enhan ced due to the shift of the electron density from the benzyl halogen a tom to the adjacent carbon atom. A topological analysis according to B ader confirmed the main reason for the change in the paramagnetic shie lding of the benzyl C-13 nuclei. The results of calculations provide, for the first time, an explanation for the resonance upfield C-13 shif t of this atom as the Hammett constant of a substituent increases in c ompounds of the series under consideration.