The use of PLS algorithms and quantum chemical parameters derived from PM3hamiltonian in QSPR studies on direct photolysis quantum yields of substituted aromatic halides

The Partial Least-Squares (PLS) method was used to further study Quantitati ve Structure-Property Relationship (QSPR) for photohydrolysis quantum yield s of selected aromatic halides. The cluster of substituted bromobenzenes an d iodobenzenes was further grouped into two clusters, substituted bromobenz enes and substituted iodobenzenes, for which QSPRs were obtained, respectiv ely. The QSPRs obtained by PLS are more significant than those obtained in previous studies. The studies showed that only when the compounds belonging to different groups are studies separately, inherent relationships between molecular properties and their structure characteristics can be revealed. It can be generally concluded that the photohydrolysis quantum yields of th e substituted aromatic halides are dependent on the overall characters of t he molecules, the characters of the carbon-halogen bonds to be broken in th e photolysis, and the character of the halogen atoms to be replaced in the photolysis. Electronegativity has great relevance to the photohydrolysis pr ocesses of the compounds. Substituted aromatic halides with large average m olecular polarizability and molecular weight values tend to have low photol ysis quantum yields. (C) 2000 Elsevier Science Ltd. All rights reserved.