Nitration of hydrogen cyanide with nitryl tetrafluoroborate

Abstract

The reaction of hydrogen cyanide at 0 °C in CFCl₃, purified nitrile-free nitromethane or tetrahydrothiophene 1,1-dioxide gave dinitrogen monoxide, N₂O and CO_n(n= 1 or 2). The same products were obtained in a solvent-free neat reaction of HCN(g) and NO₂⁺BF₄^–(s). The experimental data are in accord with the intermediate formation of neutral CN–NO₂. This intermediate then undergoes cleavage–rearrangement to give N₂O and CO. In a subsequent reaction carbon monoxide is oxidized by unreacted NO₂⁺BF₄^– to give CO₂ and the corresponding nitrosyl salt, NO⁺BF₄^–. The reaction was followed by low-temperature ¹⁴N NMR spectroscopy and the identity of the products established by ¹⁴N NMR and IR spectroscopy. The two isomers CN–NO₂ and NC–NO₂ were computed ab initio at the correlated MP2 level of theory and are discussed in terms of intramolecular stabilization by donor–acceptor interaction (negative hyperconjugation).