Quantitative structure-property relationship studies for direct photolysis rate constants and quantum yields of polybrominated diphenyl ethers in hexane and methanol.

The direct photolysis of 18 individual polybrominated diphenyl ethers (PBDEs) substituted with 1-7 bromine atoms was investigated in hexane and methanol under UV irradiation. Based on the determined photolysis rate constants (k(p)) and calculated quantum yields (Phi), four quantitative structure-property relationship (QSPR) models were developed by partial least squares (PLS) method and 20 fundamental molecular structural descriptors. The fitting results showed that all of four QSPR models had good predictability and correlations between observed and predicted photolysis data were significant. The predominant molecular descriptors governing photolysis rate constants of PBDEs in hexane were Mw; Sm; qBr; and qBr+], while in methanol the significant variables were alpha, TE, M(w) and S(m). In terms of the QSPR models for quantum yields of PBDEs in hexane and methanol, the governing molecular descriptors were almost the same. Molecular weight (M(w)) and three atomic charge descriptors (qBr, qH, qBr) were all presented in the four QSPR models, implying that photolysis rate constants and quantum yields were affected by the bromination degree and substitution pattern of PBDE molecules.