Rationalisation of ‘dissignate’ and ‘front octant’ effects of chiral ketones by a quadrant rule

Abstract

Theoretical study of a number of 2-alkanones reveals that both the normal and the abnormal (front octant and dissignate effect of substituents in rear octants) chiroptical behaviour of substituents in certain relative orientations with respect to the carbonyl group can be rationalised by a quadrant rule supplemented by a definition of the through-bond path that connects the substituent and the chromophore; the new rules are rationalised in terms of the change in the mixing of the x and y components of the total n MO orbital induced by the substituent.