Principal component analysis of long-range 'W' coupling constants of some cyclic compounds

The long-range ((4)J(HH)) coupling constants of 28 compounds, cyclopentane and cyclohexane derivatives, have been analyzed by means of principal component analysis (PCA). The corresponding dihedral angles (theta1 and theta2) and cos(2)theta (1) cos(2)theta (2), besides the 'W' constants, were utilized as variables in multivariable data analysis. Dihedral (torsion) angles were calculated utilizing three different methods: PC Model, CS Mopac Pro and GAUSSIAN98, to improve data reliability. The measured 4JHH showed a clear tendency of increasing with the variations in torsion angles from approximately 90-180 degrees, as expected. PCA allowed discrimination of the behaviour of various compounds. It was noted that the compounds analyzed exhibit strong clustering due to structural similarities. Particularly interesting results were obtained in the PCA of GAUSSIAN98 data, where seven different clusters of compounds were found. (C) 2001 Elsevier Science B.V. All rights reserved.