Kinetics and mechanisms of CH radical reactions with fluoromethanes and carbon tetrachloride

S. Zabarnick*, J. W. Fleming, Ming-Chang Lin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Laser photolysis/laser-induced fluorescence is employed to determine absolute rate coefficients for the reaction of the methylidyne radical, CH, with CH3F, CH2F2, CHF3, and CF4 over the temperature range 295-672 K. Multiphoton dissociation of CHBr3 at 266 nm forms CH radicals. Relative CH concentrations are monitored by LIF at 430 nm. The following Arrhenius parameters are obtained: k = (2.8±0.2)×10-10 exp[(280±50 cal/mol)/RT] cm3 s-1 for CH+CCl4, k = (2.0±0.2)×10-11 exp[(460±70 cal/mol)/RT] cm3 s-1 for CH+CH3F, k = (4.8±0.4)×10-12 exp[-(330±50 cal/mol)/RT] cm3 s-1 for CH+CH2, F2, k = (1.4±0.2)×10-13 exp[(40±110 cal/mol)/RT] cm3 s-1 for CH+CHF3, and k < 7×10-14 cm3 s-1 for CH + CF4. The experimental evidence supports a mechanism of CH radical insertion into CH or CCl bonds followed by fragmentation of the excited adducts as the dominant process in these reactions. The large variance in measured rate constants results mainly from steric hindrance by the unreactive CF moieties.

Original languageEnglish
Pages (from-to)311-317
Number of pages7
JournalChemical Physics
Issue number2
StatePublished - 15 Feb 1988


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