Phenol Toxicity to Fathead Minnows

Molecular connectivity indexes have been widely used to develop QSARs for toxicity and other properties of environmental interest. Hall and Kier investigated the toxicity of substituted phenols to fathead minnow [Pimephales promelasY and have shown that a two-variable equation gives good account of the toxicity data. 

A question that sometimes arises in QSAR analyses deals with the possibility of random correlations. In this study the regression equations were carefully and extensively analyzed for spurious effects due to random correlations. The regressions were repeated with randomly selected observations deleted, and no significant effects were observed in the regression equations. Further, the process of equation selection was repeated using random numbers in place of the chi indexes. No correlation obtained with the random numbers was found to be significant in comparison to that of Eq. [41]. These random number analyses have also been carried out for other QSAR investigations.  

Once a QSAR relation has been developed, a structural interpretation can be given. The direct relation of pLCso to x indicates that toxicity generally increases with an increase in molecular size for these data. It is, of course, not expected that such an increase goes to infinity, but in the data set there is no evidence of a turn-down in toxicity with increasing molecular size. The relation to the Xp index indicates two general features (I) higher row heteroatoms 

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