PRINCIPAL COMPONENT ANALYSIS AND TARGET TESTING OF SUBSTITUENT EFFECT USING CARBONYL STRETCHING FREQUENCY AND C-13 NMR CHEMICAL-SHIFT DATA MATRICES

Principal component analysis technique has been applied to analyse the substituent effect on carbonyl stretching frequency and C-13 NMR chemical shifts. The general formula for the investigated molecules is X-G-Y, where X represents the set of substituent (OMe, Me, F, Cl, Br, CN and NO2), Y is the probe site and G is benzene ring. According to the indicator function two significant components are responsible for the substituent effect. The validity of several substituent parameters have been investigated by target testing technique. Invariably substituent parameters derived by iterative multiple linear regression analysis ViZ. Sigma(R) (Reynolds), sigma(F) (Reynolds) and sigma(R) (NMR) have lower SPOIL values when compared with other substituent parameters. Model designing of IR and C-13 NMR data matrices separately have shown that models which incorporate sigma(R) (Reynolds) and sigma(F) (Reynolds) or sigma(R) (NMR) and a substituent field parameters have the lowest root mean square error RMSE. Substituent effect on several properties are better correlated with Reynolds' sigma(R) and sigma(F) than with other commonly used substituent parameter(s). The orthogonality of substituent parameters used i n the model can he achieved by including the methyl group in the substituent set.