Experimental and theoretical studies on synthesis and structure elucidation of some polychlorinated biphenyl derivatives

The regioselective methoxycarbonylation of polychlorinated biphenyls (PCBs), 2,3,4′-trichlorobiphenyl (РСВ22), and 2,5,4′-trichlorobiphenyl (PCB31), carried out in the presence of modified Co 2 (CO) 8 cobalt carbonyl catalyst proceeds with substitution of chlorine atom in the position 3 for РСВ22 and yields methyl 2-chloro-3-(4-chlorophenyl)benzoate 1 , while for PCB31 results in methyl 4-chloro-2-(4-chlorophenyl)benzoate 2 . The substitution of methoxycarbonyl group for chlorine in ortho -position of trichlorobiphenyls seems not to affect the twist angle of the biphenyl unit. However, the twist angle of the methoxycarbonyl group relative to the phenyl ring was found to be significantly larger in the meta -derivative 1 than the ortho -derivative 2 . To rationalize conformational differences between the two esters 1 and 2 in their crystal structures the optimized geometries and potential energy curves (relative energy versus torsion angle) were calculated at the B3LYP/6-31+G(d,p) level of theory.