Collect. Czech. Chem. Commun. 1990, 55, 55-62

Principal component analysis of substituent constants

Drahomír Hnyk

Institute of Inorganic Chemistry, Czechoslovak Academy of Sciences, 250 68 Řež near Prague


The principal component analysis has been applied to a data matrix formed by 7 usual substituent constants for 38 substituents. Three factors are able to explain 99.4% cumulative proportion of total variance. Several rotations have been carried out for the first two factors in order to obtain their physical meaning. The first factor is related to the resonance effect, whereas the second one expresses the inductive effect, and both together describe 97.5% cumulative proportion of total variance. Their mutual orthogonality does not directly follow from the rotations carried out. With the help of these factors the substituents are divided into four main classes, and some of them assume a special position.