AB-initio studies of N-O-F compounds. Internal rotation in hydroxylamine and its fluorinated derivatives

Ab-initio molecular orbital theory at both the minimal and extended basis set levels have been applied to the study of internal rotation in hydroxylamine and its fluorinated derivatives. The computed energies are analyzed in terms of a Fourier-type expansion of the potential function. The total potential function V(φ)can be dissected into onefold (V₁), twofold (V₂) and threefold (V₃) components and plots of these components together with V(φ) are given for each of the molecules studied herein. Additionally geometry optimizations have been carried out as a function of the internal rotation angle φ (φ = : NOX dihedral angle) for H₂NOH and F₂NOF. For H₂NOH geometry optimizations are found to be less important than for F₂NOF. In general the fluorinated hydroxylamines prefer a $\text{trans}$-conformation (φ = 180°) while hydroxylamine itself adopts the $\text{cis}$-conformation (φ = 0°) largely as a result of a lower dipole interaction (V₁ term) in the $\text{cis}$-conformation.