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Guanghui Ding

Publications and source records attributed to Guanghui Ding.

4 recordsLinked to original sources
PubMed2005

Quantitative relationships between molecular structures, environmental temperatures and solid vapor pressures of PCDD/Fs.

Based on quantum chemical and topological descriptors, temperature-dependent predictive models for solid vapor pressure (PS) of PCDD/Fs were developed. The inclusion of the two topological descriptors, Kier symmetry index (S0K) and Kier flexibility index (PHI), as predictor variables, improved the statistical significance of models. Thus the entropic factors described by the two topological descriptors play a role in influencing the PS values. The cumulative variance of the dependent variable explained by the PLS components and determined by cross-validation (Qcum2), for the final model, is 0.972, indicating that the model has good predictive ability and robustness, and could be used to estimate PS values of PCDD/Fs at different temperatures. The main factors governing log PS values of PCDD/Fs, from important to less important, are temperature, intermolecular dispersive interactions, entropic factor, and intermolecular dipole-dipole and dipole-induced dipole interactions.

Benzofurans↗
PubMed2005

Linear free energy relationships on rate constants for the gas-phase reactions of hydroxyl radicals with PAHs and PCDD/Fs.

Polyparameter linear free energy relationships (LFERs) on rate constants (kOH) for gas-phase reactions of hydroxyl radicals with polycyclic aromatic hydrocarbons (PAHs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were developed. Quantum chemical descriptors and partial least squares (PLS) regression were used for model development. Acenaphthylene was found to be an outlier and was excluded in the final model development. The cumulative variance of the dependent variable explained by the PLS components and determined by cross-validation (Q2(cum)), for the optimal model, is 0.97, indicating good robustness and predictive power of the model. The main molecular structural factor governing kOH values of PAHs and PCDD/Fs is molecular ability to donate electrons, as described by the energy of the highest occupied molecular orbital (E(HOMO)), the average of net atomic charges on hydrogen atoms (qH(+)), and the average of net atomic charges on carbon atoms (qC). PAH and PCDD/F molecules with high E(HOMO) and low qH(+) and qC values tend to have high log kOH values. The LFER model indicates the temperature dependence of log kOH is weak.

Benzofurans↗
PubMed2004

Universal predictive models on octanol-air partition coefficients at different temperatures for persistent organic pollutants.

Owing to the importance of octanol-air partition coefficients (KOA) in describing the partition of organic pollutants from air to environmental organic phases, the paucity of KOA data at different environmental temperatures, and the difficulty or high expenditures involved in experimental determination, the development of predictive models for KOA is necessary. Approaches such as this are greatly needed to evaluate the environmental fate of the ever-increasing list of production chemicals. Partial least squares (PLS) regression with 18 molecular structural descriptors was used to develop predictive models based on directly measured KOA values of selected chlorobenzenes, polychlorinated biphenyls (PCBs), polychlorinated naphthalenes, polychlorinated dibenzo-p-dioxins/dibenzofurans, polybrominated diphenyl ethers, polycyclic aromatic hydrocarbons, and organochlorine pesticides (OPs). An optimization procedure resulted in two temperature-dependent universal predictive models that explained at least 91 % of the variance of log KOA. Model 1 was the more general of the two models that could be used for all the persistent organic pollutant (POP) classes investigated. Although model 1 performed poorly for select OPs, this was attributed to wide variability in structural types within this subset of POPs and their diversity compared to the other POP classes that were investigated. The exclusion of the structurally complex OP subset resulted in a more precise model, model 5. Intermolecular dispersive interactions (induced dipole-induced dipole forces) between octanol and solute molecules play a decisive role in governing KOA and its temperature dependence. Further investigations are needed to better characterize the steric structures of the POPs under study, especially of OPs.

Air↗