Linear solvation energy relationship descriptors of organophosphorus chemical warfare agents

The linear solvation energy relationships (LSER) model of Abraham is widely used to describe solute partitioning between liquid-liquid and gas-liquid systems. The model employs solute descriptors and system coefficients to quantify intermolecular interactions, enabling prediction of solute distribution in systems relevant to chemistry, environmental science, medicine, and biology. In this study, LSER descriptors were determined for seven organophosphorus compounds, including the nerve agents tabun (GA), sarin (GB), and soman (GD). The E descriptor (molecular polarizability) was derived from literature refractive indices, while the V descriptor (McGowan characteristic volume) was calculated from atomic fragments and bonds. The S (dipolarity) and L (dispersion interactions) descriptors were obtained using gas chromatography on six capillary columns with diverse solvation properties. The A descriptor (hydrogen-bond acidity) was assumed to be zero based on molecular structure. The B descriptor (hydrogen-bond basicity) was estimated from literature partition coefficients in liquid-liquid and gas-liquid systems; however, its reliability is limited due to sparse and scattered data. The descriptor values obtained for selected reference compounds showed good agreement with literature data, confirming the validity of the methodology. Additionally, LSER descriptors were estimated using QSAR models, but noticeable discrepancies were observed, likely due to the limited representation of organophosphorus compounds in model parameterization.