Quantitative structure-activity relationship regression constant

QSAR Quantitative structure-activity relationship. Quantitative structure-bio-logical activity model derived using regression analysis and containing as parameters physical-chemical constants, indicator variables, or theoretically calculated values. 

Methods other than thermodynamic cycles are often used to calculate acid dissociation constants. Previous publications implement the theoretical relationship between pKa and structural property [6], bond valence methods and bond lengths [33], pKa correlations with highest occupied molecular orbital (HOMO) energies and frontier molecular orbitals [34], and artificial neural networks [35] to predict pKa values. In addition much work has been done using physical properties as quantitative structure-activity relationship (QSAR) descriptors, and regression equations with such descriptors to yield accurate pKa values for specific classes of molecules [36-47]. The correlation of pKas to various molecular properties, however, is often restricted to specific classes of compounds, and it is... 

Quantitative structure-activity relationships for fathead minnow Pimephales promelas) LC50 data were developed. As others have observed, log toxicity and log octanol/water partition coefficent (log P) are linearly related for alcohols (n = 20), alkyl ketones (n = 14), alkyl esters (n = 16), and alkyl nitriles (n = 8). When the sums of Taft sigma constants for the substituents of the most anionic carbon in each chemical structure were included in the regression of log LC50 versus log P, the coefficient of determination (r ) improved from 0.84 (for log P only) to 0.92 for alcohols, from 0.82 to 0.92 for ketones, from 0.77 to 0.91 for esters, and from 0.15 to 0.94 for nitriles. The r for the sum of Taft sigma constants versus LC50 for each class was less than 0.17. When the sum of a, was used instead of Taft sigma constants similar results were obtained. 

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