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 compo nent analysis (PCA). The corresponding dihedral angles (theta1 and theta2) and cos(2)theta (1) cos(2)theta (2), besides the 'W' constants, were utiliz ed as variables in multivariable data analysis. Dihedral (torsion) angles w ere calculated utilizing three different methods: PC Model, CS Mopac Pro an d GAUSSIAN98, to improve data reliability. The measured 4JHH showed a clear tendency of increasing with the variations in torsion angles from approxim ately 90-180 degrees, as expected. PCA allowed discrimination of the behavi our 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.