Energetics of HF elimination and NF bond cleavage in some difluoramines and gem-nitro/difluoramines

Abstract

We have shown, through density functional calculations (Becke exchange/Lee, Yang and Parr correlation functional, 6-31G ∗∗ basis set) that the elimination of HF from H 3CNF 2 is thermodynamically favored, ΔG(298.15 K) = −29kcal mol −1, but has a relatively high activation barrier, ΔG‡(298.15 K) = 38 kcal mol −1 . The NF dissociation energy, ΔE N F , is found to be 69 kcal mol −1. Introduction of a nitro group, giving H 2C(NO 2)NF 2, produces only small changes in these values: ΔG(298.15 K) = −28 kcal mol −1; ΔG‡(298.15 K) = 36 kcal mol −1 ; ΔE N F = 66 kcal mol −1. Replacement of all alpha hydrogens by methyl groups increases the NF dissociation energies slightly (< 2 kcal mol −1). These substituent effects are interpreted in terms of geminal interactions.