Structure-toxicity relationships for selected benzyl alcohols and the polar narcosis mechanism of toxicity.

The relative toxicity of 20 ortho-, meta-, and para-position monoalkylated or monohalogenated benzyl alcohols has been determined as 50% population growth inhibition (log BR; biological response) to Tetrahymena pyriformis. Linear relationships are observed between log BR and the 1-octanol/water partition coefficient (log Kow) for both the alkylated and the halogenated series. Regression analysis of the combined data results in poor correlation with the model, log BR = 0.7085(log Kow) - 1.3018; n = 20, r2 = 0.644, s = 0.323. However, the predictability of this quantitative structure-activity relationship (QSAR) is sharply enhanced by the addition of the Hammett sigma constant (sigma) as a second molecular descriptor, log BR = 0.8395(log Kow) + 1.4322 (sigma) - 1.6823; n = 20, r2 = 0.923, s = 0.154. This latter QSAR uses the para-position sigma as an estimator of ortho-position effects and compares well with previous work with alkyl- or halogen-substituted phenols. It is thought to model the polar narcosis mode of toxic action.