Kinetics of CH(X2Π) radical reactions with propane, isobutane and neopentane

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

*Corresponding author for this work

Research output: Contribution to journalArticle

16 Scopus citations

Abstract

Rate constants over the temperature range 298-689 K are reported for the reaction of CH(X2Π) radicals with C3H8, i-C4H10 and neo-C5H12. The CH radical was generated by multiphoton laser photolysis of CHBr3 and its disappearance monitored by laser-induced fluorescence (LIF) at 429.8 nm. Absolute rate constants were determined as a function of temperature and total pressure. The following Arrhenius parameters were derived: k = (1.85 ± 0.13) × 10-10 exp[(240±30)/T] cm3/s for CH+propane; k = (2.03±0.19)×10-10 exp[(240±40)/T] cm3/s for CH+isobutane; k = (1.61±0.10)×10-10 exp[(340±30)/T] cm3/s for CH+neopentane, all independent of total pressure. The negative temperature dependences along with the energetics and lack of pressure effects lead to the conclusion that the reactions proceed by CH insertion into the alkane. The activated adduct thus formed rapidly decomposes via many energetically accessible channels. An analysis of CH reactions with C1 to C5 alkanes shows an increase in the room temperature rate constants in going from C1 to C4 irrespective of the nature of CH bonds. The rate constant then begins to level off near ≈ 5 × 10-10 cm/s for C4 and C5 alkanes.

Original languageEnglish
Pages (from-to)409-413
Number of pages5
JournalChemical Physics
Volume112
Issue number3
DOIs
StatePublished - 15 Mar 1987

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