Structure-activity relationships of selected pyridines: Substituent constant analysis

Twenty-two four-position derivatives of pyridine (C sub(5)H sub(5)N) were tested following an acute static regime with biological response being monitored as population growth of Tetrahymena pyriformis). The vinyl derivative was the most active and the hydroxy derivative was the least active. Structure-activity relationships were examined using substituent constants as molecular descriptors. Size/shape parameters and hydrophobic/hydrophilic parameters found to be more important descriptors than electronic parameters. Following the deletion of the outliers, 4-vinylpyridine and 4-nitropyridine, molar refractivity was found to be the best single descriptor explaining 62.5% of the variability in biological response. Based on highest adjusted r super(2) value the best model is log BR = 0.0055 (MR) - 0.3699 (H sub(a)) - 1.0124, r super(2) = 0.709 (BR, biological response; MR, molar refractivity; H sub(a), hydrogen acceptance). Models using P sub(i) (hydrophobic substituent constant) as the descriptor and comparisons with previously assayed naphthalenes are discussed.