Proton affinity of FNO

Protonation of the nitrogen of nitrosyl fluoride (FNO) is favored over protonation at the oxygen site. The proton affinity of FNO at the nitrogen site is determined to be 124.0±3 kcal mol−1. The energy separation between structures protonated at the nitrogen and oxygen sites is 5.5±3 kcal mol−1. Protonation at the fluorine site results in a HF–NO+ complex which is lower in energy than the other two structures. The single and double coupled-cluster method that includes a perturbational estimate of the effects of connected triple excitations, denoted CCSD(T), was used in conjunction with split valence triple-zeta and the correlation consistent basis sets to arrive at these values.