Inter- and intra-molecular two-centre three-electron bonding in radical cations of alkyl bromides

Abstract

The reaction of hydroxyl radicals with different alkyl bromides in acidic aqueous solution has been studied by nanosecond pulse radiolysis technique at a high solute concentration where solute dimer radical cations are formed. The observed rate constant for the decay of dimer radical cations is deconvoluted to different processes and the deprotonation of the radical cation is found to be the rate determining step. The inter- and intra-molecular two-centre three-electron bond strength is determined for a series of radical cations from alkyl bromides and dibromoalkanes at a semi-empirical level with AM1 parametrization. Calculations indicate that the strengths of hemi-bond decreases as the length of methylene linkage increases in case of dimer radical cations.