QSPRs on photodegradation half-lives of atmospheric chlorinated polycyclic aromatic hydrocarbons associated with particulates.

A quantitative structure-property relationship (QSPR) model which could predict photodegradation half-lives (t(1/2)) of chlorinated polycyclic aromatic hydrocarbons (ClPAHs) associated with particulates in the atmosphere was developed by applying quantum chemical parameters computed with quantum chemical PM3 algorithm and using a partial least squares (PLS) algorithm. The cross-validated Q(2)(cum) value for the optimal QSPR model is 0.960, indicating a good predictive capability for logt(1/2) values of ClPAHs. The QSPR results show that the main factors affecting logt(1/2) values of ClPAHs are the energy of the second highest occupied molecular orbital (E(LUMO-1)), the energy of the second highest occupied molecular orbital (E(HOMO+1)), average molecular polarizability (alpha), the most positive net atomic charges on a hydrogen atom (Q(H)(+)), E(LUMO)+E(HOMO), E(LUMO)-E(HOMO), and (E(LUMO)-E(HOMO))(2). ClPAHs with high E(LUMO-1), E(HOMO+1), E(LUMO)-E(HOMO,) and (E(LUMO)-E(HOMO))(2) values tend to photolyze slowly in the atmosphere. In contrast, increasing E(LUMO)+E(HOMO), alpha, and Q(H)(+) values leads to the increase of photodegradation rates.