Statistical analysis of chemical reactivity data. Part 5. Aliphatic substituent effects

Abstract

We have shown with the aid of principal component analysis combined with a cross-validation technique that a two-term linear free energy relationship (l.f.e.r.) is needed to correlate the data within a set of alkyl-substituted reaction series. It has not been possible to extend the validity of this two-term l.f.e.r. to include CH₂Ph. This substituent in combination with alkyl substituents needs a three-term l.f.e.r. Due to the lack of data it was not possible to confirm if other substituents of the type CH₂X (X = polar group) can be described with the same two-term l.f.e.r. as the alkyl substituents.