Carbonylation of ammonia by gaseous FCO+. A G2 and Rice-Ramsperger-Kassel-Marcus study of the detailed mechanistic aspects

The detailed mechanism of the gas-phase carbonylation of NH, by FCO+ with f ormation of H2NCO+ and HF has been theoretically investigated by G2 and Ric e-Ramsperger-Kassel-Marcus (RRKM) calculations. The results provide a coher ent description of the experimental evidence, so far obtained by Fourier tr ansform ion cyclotron resonance spectrometry. The detailed G2 potential ene rgy surface of the reaction has been used to outline the corresponding kine tic scheme, whose rigorous formulation has been simplified by making assump tions based on the explicit evaluation of all the involved kinetic constant s, calculated according to the RRKM theory. It was possible to estimate the efficiency of the reaction for different alternative mechanisms and to com pare the obtained values with the experimentally measured efficiency, used as a probing reference value. The obtained results indicate that the reacti on occurs by a "composite" mechanism, which involves the initial formation of an adduct between FCO+ and NH3 and the subsequent loss of HF by two dist inct paths. In addition, it was possible to conclude that the only ionic pr oduct expected from the reaction is the H2N-CO+ isomer. (Int J Mass Spectro m 184 (1999) 89-101) (C) 1999 Elsevier Science B.V.