The interrelation between the structural, electronic and energy parameters of nitrogen inversion in ammonia derivatives

Abstract

The structural, electronic and energy parameters in the ground and transition states of inversion of the amines H2NXHn (XHn=CH3, NH2, OH, F, SiH3, PH2, SH, and Cl) have been calculated by using DFT (PBE96/def2-tzvpp) method. It was established that the increase of electronegativity of the substituents (the X atoms within the same period) leads to stabilization of the ground and transition states of the molecules. The increase in the inversion barriers is due to relative stabilization of the ground states, but not due to relative destabilization of the transition states. The inversion barriers rise with a decrease in conformational energies of the substituents, sums of valence angles at the nitrogen atoms, negative charges on them, energies of the nitrogen lone pairs and with an increase in s-character and population of the nitrogen lone pairs and difference between the energies of the nitrogen lone pairs in the ground and transition states. The main parameters that allow predicting the change of the nitrogen inversion barriers, independently of the type or volume of the XHn substituent, are s-character of the nitrogen lone pairs and difference between the energies of the nitrogen lone pairs. In all other cases, the correlations were found only for the amines containing the elements of the same period at the nitrogen atom. All structural and electronic parameters of amines containing the Х atoms from the second period are more sensitive to the changes of the ХНn substituents than the parameters of amines containing the Х atoms from the third period.