Kinetics and mechanisms of the reactions of CH and CD with H2 and D2

Michael R. Berman*, Ming-Chang Lin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

64 Scopus citations


The reactions CH + H2k1products and CD + D 2k2products were studied using a laser photolysis/laser-induced fluorescence (LIF) technique. The room-temperature rate constant for reaction (1) was found to be pressure dependent between 25 and 600 Torr. Reactions (1) and (2) were studied as a function of temperature in the range 159-658 K at a total pressure of 100 Torr. Two pathways dominate these reactions. Below 400 K, addition followed by collisional stabilization of the adduct predominates. The rate constants display negative temperature dependences and are described by k1 = (2.37 ± 0.43) × 10 -12 exp[(1041 ± 85)/RT] and k2 = (3.51 ± 0.58) × 10-12 exp[(1030 ± 90)/RT] cm3 molecule-1 s-1 with Ea in units of cal mol -1. Above 500 K, production of CH2 + H or CD2 + D with an activation energy of 4 ± 2 kcal mol-1 dominates. In the reactions of CH + D2 and CD + H2, anomalously fast removal of the parent radical is observed because of formation and dissociation of chemically activated addition complexes which lead to isotopically substituted parent radicals. LIF spectra of these product radicals were obtained. A transition-state-theory model was applied to a mechanism in which collision stabilization and product formation proceed through a single complex.

Original languageEnglish
Pages (from-to)5743-5752
Number of pages10
JournalThe Journal of chemical physics
Issue number12
StatePublished - 1 Jan 1984


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