Solid state nuclear bromination with N-bromosuccinimide. Part 2. Experimental and theoretical studies of reactions with some substituted benzaldehydes

N-Bromosuccinimide reacts with aromatic aldehydes in the solid state to yie ld exclusively nuclear brominated products while a similar reaction in the solution phase produces a number of products under varied conditions. The r eactivity and regioselectivity have been studied in terms of the energies o f HOMO, HOMO-LUMO difference, reaction free energy, reaction conditions and crystal packing. Single crystal X-ray structural analysis of 3,4-dihydroxy benzaldehyde has been carried out. Crystal packing energies of some of the reactive and unreactive benzaldehydes indicate the importance of molecular bromine diffusion in the solid state.