Absolute rate constant for the reaction of Phenyl radical with Acetylene

The absolute rate constant for the reaction of phenyl radical with acetylene has been measured at 20 torr total pressure in the temperature range of 297 to 523 K using the cavity‐ring‐down technique. These new kinetic data could be quantitatively correlated with the data obtained earlier with a relative rate method under low‐pressure (10 −3 –10 −2 torr) and high‐temperature (1000–1330 K) conditions. These kinetic data were analyzed in terms of the RRKM theory employing the thermochemical and molecular structure data computed with the BAC‐MP4 technique. The calculated results reveal that the total rate constant for the C 6 H 5 + C 2 H 2 reaction ( k t ) is pressure‐independent, whereas those for the formation of C 6 H 5 C 2 H ( k b ) and the C 6 H 5 C 2 H 2 adduct ( k c ) are strongly pressure‐dependent. A least‐squares analysis of the calculated values for 300–2000 K at the atmospheric pressure of N 2 or Ar can be given by\documentclass{article}\pagestyle{empty}\begin{document}$$ k_b = 9.5 \times {\rm 10}^{{\rm - 42}} T^{9.33} \exp \left({- 1,713/T} \right) $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ k_C = 1.8 \times {\rm 10}^{{\rm - 7}} T^{-1.63} \exp \left({- 2,711/T} \right) $$\end{document}and\documentclass{article}\pagestyle{empty}\begin{document}$$ k_t = 4.1 \times {\rm 10}^{{\rm - 18}} T^{1.77} \exp \left({- 1,152/T} \right) $$\end{document}all in units of cm 3 /s. The latter equation effectively represents the two sets of experimental data. © 1994 John Wiley & Sons, Inc.