QSAR of General Anesthetics

The anesthetic potencies of a set of hydrocarbons, ethers, and ketones were examined by DiPaolo. The potency is represented as pC,ff = - log(c,.ff), where Ceff is the effective anesthetic concentration. The experimental error is reported as 0.17. In the analysis, DiPaolo reported that the dependence on molecular size was best given by x but that the relation is inversely proportional. Further, the valence chi path index of order four is required to provide the QSAR equation of high quality  

The equation accounts for 89% of the variance in the potency, and the standard error is at the level of the reported experimental error. DiPaolo showed that a plot of potency versus reveals nonlinear dependence with a maximum point. However, a quadratic form is not able to unite the data for all three classes of compounds into a single equation. It is the combination of the reciprocal of x together with Xp that gives a single equation for the three chemical classes. Examination of the equation indicates that the maximum occurs at X = 4.5 and Xp = 0.863, values near to those for butyl propionate and propyl butyrate. 

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