The enthalpy change and the detailed rate coefficients of the equilibrium reaction OH+C2H2⇌HOC2H2 over the temperature range 627-713 K

Lih Huey Lai*, Yen Chung Hsu, Yuan-Pern Lee

*Corresponding author for this work

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Abstract

The reaction between OH and C2H2 in He has been studied over the pressure range 414-864 Torr and the temperature range 627-713 K by means of the laser-photolysis/laser-induced-fluorescence technique. Analysis of the temporal profile of [OH] yielded the forward and the reverse rate coefficients, hence the equilibrium constant for the reaction OH+C 2H2+⇌HOC2H2+M. The temperature dependence of the equilibrium constant yielded the enthalpy of reaction ΔH(670±43 K) = -(34.2±1.0) kcal mol-1 and the entropy of reaction AS(670±43 K) = -(30.5±1.2) cal K -1 mol-1 near 670 K; consequently, ΔH0 (298 K) = -(33.6±1.2) kcal mol-1 and ΔS0 (298 K) = -(28.9±1.5) cal K-1 mol-1 were derived for the reaction, in agreement with theoretical prediction. The temperature dependence of the rate coefficients for the forward, the reverse, and the adduct-loss (isomerization/decomposition other than the reverse) reactions near 1 atm have been determined to be kf = (1.1 ± 0.2) × 10-13 exp[(1460 ± 500)/T] cm3 molecule-1 s-1, kr = (2.2 ± 0.4) × 1012 exp[ - (15 100 ± 600)/T] s-1, and ka = (7.4 -5.6+0.2) × 1010 exp[ - (13 200 -1700+700)/T]s-1, respectively.

Original languageEnglish
Pages (from-to)3092-3099
Number of pages8
JournalThe Journal of chemical physics
Volume97
Issue number5
DOIs
StatePublished - 1 Jan 1992

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