Gas-Phase Chemistry of NHxCly⁺. 1. Structure, Stability, and Reactivity of Protonated Monochloramine

The structure and the reactivity of gaseous NH 3 Cl + ions obtained from direct protonation of aqueous monochloramine by CI/CH 4 and from ionization of a Cl 2 plasma containing trace amounts of ammonia have been investigated by FT-ICR mass spectrometry. The results characterized the NH 3 Cl + ions arising from both experiments as having the NH 3 −Cl + structure, consistent with the results of MO SCF calculations pointing to the higher basicity of the nitrogen than the chlorine atom of NH 2 Cl. The gas-phase basicity of monochloramine has been estimated to be 761 ± 5 kJ mol -1 from bracketing experiments according to the procedure based on the relationship between the efficiency and the standard free-energy difference of proton transfer. This value is consistent with those from theoretical calculations at the B3LYP and CCSD(T)/6-311++G(3df,3pd) level. In agreement with the protonation site, the NH 3 Cl + ions behave as a protonating and chlorinating agent but addition is also observed.