P, π-interaction in the group using the NQR technique and MNDO calculations

Abstract

The experimental EFG asymmetry parameters at the halogen nuclei in molecules containing the group do not corroborate widespread representations of a p, π-conjugation between the unshared electron pair of the halogen atom and the π-electron double bond system in these molecules. MNDO calculations of ethylene and its derivatives and analysis of p x -orbital populations of the C and Y atoms in the group of these molecules conform to the experimental data in question. These calculations as well as those of XCH=CH 2 (X=F, Cl and CH 3 ) molecules with varying CX bond lengths, and systems XCH=Ch 2 −HF and [XCH=CH 2 ] 1+ − HF with varying distance between the system fragments, conform to an electrostatic mechanism of p x -electron density distribution in such molecules.