Gas-phase reactions of protonated chlorine, Cl2H+, with H2(D2) and CH4. A mass spectrometric and theoretical study

Article abstract of DOI:10.1016/S0009-2614(99)00313-9

FT-ICR (Fourier Transform Ion Cyclotron Resonance) experiments showed that the reaction of Cl₂H⁺ with H₂ (rate coefficient 6.3±1.0 cm³ s^-1 molecule^-1 at 298 K) yields ClH₂⁺ ions, identified as protonated hydrochloric acid by CAD (Collisionally Activated Decomposition) mass spectrometry. Calculations performed at the B3LYP and CCSD(T) levels of theory show that the reaction involves insertion of the terminal Cl atom of Cl₂H⁺ into the H-H bond, which accounts for the experimental observation that ClD₂⁺ but not ClHD⁺ is formed from the reaction of Cl₂H⁺ with D₂. The same Cl⁺ insertion mechanism characterizes the reaction of Cl₂H⁺ with CH₄, whose product was identified as protonated methyl chloride, CH₃ClH⁺, by CAD mass spectrometry.