Reactivity of congeners of Sovol technical mixture of polychlorinated biphenyls toward sodium methoxide

Abstract

The reaction of Sovol technical mixture of polychlorobiphenyls with sodium methoxide in bipolar aprotic solvents was studied. The reactivity of polychlorobiphenyls was evaluated using gas chromatography and gas chromatography3mass spectrometry.

Reactivity features of polychlorobiphenyl congeners in the nucleophilic substitution reactions

“…The interaction of the obtained groups of congeners with sodium methoxide was effected under the conditions described in [10] along the Scheme 2. The composition of the resulting mixtures of the PCB methoxy derivatives is shown in the table.…”

“…For example, the use of the nanosized Pd and/or Fe catalysts in the processes of reductive dehalogenation of the PCB congeners in some cases leads to comprehensive conversion (100%) of the principal compounds [1-8]. As a rule, the dehydrohalogenation of the highly chlorinated congeners results in a mixture of rather less chlorinated biphenyls, and these methods can serve as a preliminary stage to biodegradation of the chlorinated products and the subsequent removal of chlorine atoms from the substrate.The stage of preliminary preparation of PCBs for disposal can also be performed using reactions of nucleophilic substitution of chlorine atoms in the PCB congeners [9].We have shown previously that in the reaction of technical mixtures of the PCBs of "Sovol" brand with sodium methoxide the most reactive congeners are hexa-and pentachlorobiphenyls, while tetra-and trichlorobiphenyls are less reactive [10]. In this reaction the hexachlorobiphenyls (PCB 128, PCB 132, PCB 138, PCB 149, PCB 153, and PCB 156) were transformed into di-and trimethoxy derivatives, the pentachlorobiphenyls (PCB 82, PCB 85, PCB 87, PCB 91, PCB 95, PCB 97, PCB 99, PCB 101, PCB 105, PCB 110, and PCB 118), into mono-, di-and trimethoxy derivatives (to a low extent), tetrachlorobiphenyls (PCB 41, PCB 47, PCB 49, PCB 56, PCB 60, PCB 64, PCB 66, PCB 70, and PCB 74), into mono-and dimethoxy derivatives (to a low extent), trichlorobiphenyls (PCB 28 and PCB 33) into monomethoxy derivatives (partially).…”

“…We have shown previously that in the reaction of technical mixtures of the PCBs of "Sovol" brand with sodium methoxide the most reactive congeners are hexa-and pentachlorobiphenyls, while tetra-and trichlorobiphenyls are less reactive [10]. In this reaction the hexachlorobiphenyls (PCB 128, PCB 132, PCB 138, PCB 149, PCB 153, and PCB 156) were transformed into di-and trimethoxy derivatives, the pentachlorobiphenyls (PCB 82, PCB 85, PCB 87, PCB 91, PCB 95, PCB 97, PCB 99, PCB 101, PCB 105, PCB 110, and PCB 118), into mono-, di-and trimethoxy derivatives (to a low extent), tetrachlorobiphenyls (PCB 41, PCB 47, PCB 49, PCB 56, PCB 60, PCB 64, PCB 66, PCB 70, and PCB 74), into mono-and dimethoxy derivatives (to a low extent), trichlorobiphenyls (PCB 28 and PCB 33) into monomethoxy derivatives (partially).…”

“…Given that Sovol is a mixture of 30 PCB congeners [11,12], the results of the study [10] are approximate and practically do not give information on the most reactive C-Cl bonds in the structures of individual chlorinated biphenyls within a single series of isomers. The error in determining the number and types of methoxy derivatives of PCBs in [10] appears both due to the different responses of the flame-ionization detector to the components of the initial and final products, and due to the coincidence in the retention times on the GC column at elution of some derivatives.…”

“…The error in determining the number and types of methoxy derivatives of PCBs in [10] appears both due to the different responses of the flame-ionization detector to the components of the initial and final products, and due to the coincidence in the retention times on the GC column at elution of some derivatives. A complete list of the methods of synthesis of the PCB congeners by the aryl-aryl coupling is given in [13].…”