C12–30 α‑Bromo-Chloro “Alkenes”: Characterization of a Poorly Identified Flame Retardant and Potential Environmental Implications

Bromo-chloro alkenes (Br-Cl PXAs) have been used for over 30 years as flame retardants and are listed on several national chemical inventories. Very little publicly available information is available on Br-Cl PXAs, and thus preliminary ecological risk screening is challenging due to the lack of basic information such as molecular structure and associated physicochemical properties. Due to their likely similarity with chlorinated paraffins (CPs), Br-Cl PXAs may pose a similar environmental hazard. Several structural databases list such substances as "alkenes", although the industrial synthesis involves halogenation of linear alpha-olefins and would be expected to produce linear alkanes. In this study, a combination of high-resolution separation and mass spectrometric techniques were used to characterize a Br-Cl PXA industrial technical product, C_12-30 bromo-chloro alpha-alkenes (CAS RN 68527-01-5). The results show this product is dominated by C₁₈ carbon chain lengths, substituted with 3-7 chlorine atoms and 1-3 bromine atoms on an alkane chain. Long-chain C₁₈ chlorinated paraffins are also present, although they represent a relatively minor component. Experimental log K_OW (6.9 to 8.6) and estimated log K_OA (10.5 to 13.5) and log K_AW (-5.1 to -0.6) partition coefficients suggest that this chemical will behave similarly to medium- and long-chain CPs as well as other persistent organic pollutants, such as highly chlorinated pesticides and polychlorinated biphenyls. The results of this study provide an initial step toward understanding the environmental behavior and persistence of Br-Cl PXAs, highlighting the need for further assessment and re-evaluation of the current structure(s) assigned to these compounds.