Conversion of CH4 to CH3OH: Reactions of CoO+ with CH4 and D2, Co+ with CH3OD and D2O, and Co+(CH3OD) with Xe

Article abstract of DOI:10.1021/ja00096a044

The mechanisms and energetics involved in the conversion of CH₄ to CH₃OH by CoO⁺ are examined by using guided ion beam mass spectrometry. The forward and reverse reactions, CoO⁺ + CH₄ ? Co⁺ + CH₃OH, the collisional activation of Co⁺(CH₃OH), and the related reactions, CoO⁺ + D₂ ? Co⁺ + D₂O, are studied. It is found that the oxidations of methane and D₂ by CoO⁺, both exothermic reactions, do not occur until overcoming activation barriers of 0.56 ± 0.08 and 0.75 ± 0.04 eV, respectively. The behavior of the forward and reverse reactions in both systems is consistent with reactions that proceed via the insertion intermediates R-Co⁺-OH, where R = CH₃ or H. The barrier is probably attributable to a four-centered transition state associated with addition of RH across the CoO⁺ bond. In the Co⁺ + CH₃OH system (where CH₃OD labeled reactant is used), reactions explained by initial C-H and O-H activation are also observed. The reaction mechanisms and potential energy surfaces for these systems are derived and discussed. Phase space theory calculations are used to help verify these details for the CoO⁺ + D₂ system. Thermochemistry for several species including CoOH⁺, CoD⁺, CoH, CoCH₃⁺, Co⁺(CH₃OD), CoOCH₃⁺, and possibly OCoCH₃⁺ is derived from measurements of reaction thresholds.