QSAR Studying of Oxidation Behavior of Benzoxazines as an Important Pharmaceutical Property.

In this work the electrooxidation half-wave potentials of some Benzoxazines were predicted from their structural molecular descriptors by using quantitative structure-property relationship (QSAR) approaches. The dataset consist the half-wave potential of 40 benzoxazine derivatives which were obtained by DC-polarography. Descriptors which were selected by stepwise multiple selection procedure are: HOMO energy, partial positive surface area, maximum valency of carbon atom, relative number of hydrogen atoms and maximum electrophilic reaction index for nitrogen atom. These descriptors were used for development of multiple linear regression (MLR) and artificial neural network (ANN) models. The statistical parameters of MLR model are standard errors of 0.016 and 0.018 for training and test sets, respectively. Also, these values are 0.012 and 0.017 for training and test sets of ANN model, respectively. The predictive power of these models was further examined by leave-eight-out cross validation procedure. The obtained statistical parameters are Q2 = 0.920 and SPRESS = 0.020 for MLR model and Q2 = 0.949 and SPRESS = 0.015 for ANN model, which reveals the superiority of ANN over MLR model. Moreover, the results of sensitivity analysis on ANN model indicate that the order of importance of descriptors is: Relative number of H atom > HOMO energy > Maximum electrophyl reaction index for N atom > Partial positive surface area (order-3) > maximum valency of C atom.

Ab Initio Intermolecular Potential Energy Surface of CO2-C2H2 Complex.

A new four-dimensional potential energy surface for CO2-C2H2 complex has been calculated by the ab initio methods at MP2/cc-pVXZ and MP2/aug-cc-pVXZ theory. For calculating the PES of the CO2-C2H2 complex, we have chosen to follow the supermolecule approach. The complete basis set limit of potential energy surface has been taken by extrapolation. Our MP2 results showed the most stable form of CO2-C2H2 complex is a parallel configuration. The complete basis set limit of ab initio potential energy surfaces have fitted to an analytic function and performance of fitting assessed. The electrostatic contribution to the PES has calculated and shows that it is anisotropic.