Structure and Natural Bond Orbital Analysis of Oxiranes Substituted with a Group 14 Element. A Comment of SN2 Regioselectivity

Crystal structure analysis of oxiranes substituted with a group 14 element revealed that silyl and stannyl groups lengthened their (alpha) C-O bonds. Natural bond orbital analysis showed that silyl group raised the energy level of (alpha) C-O (sigma) orbital and lowered that of (alpha) C-O (sigma)* orbital. It was suggested that the former might lengthen the (alpha) C-O bond and that the latter should affect the regioselectivity in ring-opening reactions.