Substituent effects 312 GENERAL INDEX

The susceptibility or mixing coefficients, pj and pj , depend upon the position of the substituent (indicated by the index, /) with respect to the reaction (or detector) center, the nature of the measurement at this center, and the conditions of solvent and temperature. It has been held that the p/scale of polar effects has wide general applicability (4), holding for substituents bonded to an sp or sp carbon atom (5) and, perhaps, to other elements (6). The or scale, however, has been thought to be more narrowly defined (7), holding with precision only for systems of analogous pi electronic frameworks (i.e., having a dependence on reaction type and conditions, as well as on position of substitution). 

MR is generally scaled by 0.1 and used in biological QSAR, where intermolecular effects are of primary importance. The refractive index of the molecule is represented by n. With alkyl substituents, there is a high degree of collinearity with hydrophobicity hence, care... 

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