AbstractThe thermal stability and composition of the gas phase of Sovol technical mixture of polychlorobiphenyls was studied by synchronous thermal analysis and mass spectrometry in comparison with the derivatives synthesized by the reaction of the congeners with sodium methoxide or with polyethylene glycol in the presence of alkali. The obtained mixtures of methoxy + hydroxy + methoxyhydroxy or hydroxy + poly(ethylene glycol)oxy derivatives of polychlorobiphenyls are less stable thermally than the congeners of the Sovol mixture. In pyrolysis of a mixture of methoxy, hydroxy, and methoxyhydroxy derivatives, the vaporization is accompanied by decomposition with the formation of simple volatile substances. No vaporization is observed in the course of oxidative thermal decomposition of a mixture of hydroxy and poly(ethylene glycol)oxy derivatives. Thermal decomposition of the derivatives requires lower power consumption compared to polychlorobiphenyls and is characterized by decreased emission of hazardous chlorinated compounds.