Relationship of the selectivity effect of aromatic solvents with their electron-donor ability and organic reactant structure in free radical chlorination

effect of several solvents on the selectivity of the free radical chlorinat ion of I,l-dichloroethane and 1-chloropropane is studied. The selective act ion of aromatic solvents on free radical chlorination is explained. This ex planation implies that the process involves solvated chlorine atoms and the ir donor-acceptor complexes with aromatic molecules (ArH-->Cl-.) as interme diates. Using the findings of this work and previous studies, the ratios of the rate constants for hydrogen-atom abstraction from different positions in chloroethane, I,l-dichloroethane, 1-chloropropane, and 2-chloropropane b y solvated chlorine atoms and ArH-->Cl-. complexes are determined. The diff erences in the activation energies of the competitive hydrogen-atom abstrac tions from different positions in substrates by the ArH-->Cl-. complexes an d solvated chlorine radicals correlate with two HOMO energies of solvent an d substrate molecules. The isokinetic relationship is found for all the sys tems under study (the isokinetic temperature, 523 K).