ESTIMATION OF HAMMETT SIGM-CONSTANTS FROM CALCULATED ATOMIC CHARGES USING PARTIAL LEAST-SQUARES REGRESSION

Hammett constants describe the electronic donating or withdrawing capa bilities of a given substituent. Since Hammett constants represent inf ormation of an electronic nature, their values are to be linked with a tomic charges and orbital-derived parameters of the atoms of the subst rate bearing the substituent. A series of 132 para- and meta-substitut ed benzoic acid structures has been built and energy minimized using M OPAC/AM1. Atomic charges and frontier orbital coefficients of the benz oic moiety have been calculated. These parameters were highly interrel ated. Using partial least squares regression, we showed that Hammett c onstants can be satisfactorily estimated from these electronic paramet ers. (C) 1996 by John Wiley & Sons, Ltd.