Thermal Properties of Nitro Derivatives of Polychlorobiphenyls

As a result of transboundary transport through the air, water, and food chains, polychlorobiphenyls—persistent organic pollutants—have spread everywhere over the period of their production and use as dielectric fluids. Nitro derivatives of polychlorobiphenyls—secondary pollutants—are also hazardous to the environment and people, but their thermal properties have not yet been studied in sufficient detail. The purpose of this work is to study the thermal properties of nitro derivatives of polychlorobiphenyls. We analyze synthesized nitro derivatives of polychlorobiphenyls present in the composition of Trichlorobiphenyl and Sovol commercial mixtures. Simultaneous thermal analysis data indicate that mixtures of the nitro derivatives tend to undergo sublimation, rather than thermal decomposition. We have determined their sublimation onset temperatures and enthalpies of sublimation. The thermal stability of the nitro derivatives has been shown to decrease as the number of chlorine substituents in the structure of biphenyl increases. Moreover, with increasing ambient temperature, polychlorinated nitroarenes can pass into the boundary atmospheric layer, which is characterized by temperature inversion and increased pollution. The results of this study can be helpful in improving techniques for monitoring nitro derivatives of polychlorobiphenyls in environmental entities.