O + C2H2 -> CO + CH2

SOURCE:

The overall rate coefficient for O + C2H2 -> Products,

21. O + C2H2 -> H + HCCO
22. O + C2H2 -> OH + C2H
23. O + C2H2 -> CO + CH2,

is from Michael and Wagner (1990) for the main channels k21 and k23. A 34% branching fraction was used for k(23)/k(23)+k(21).

COMMENTS:

The branching fraction for the H atom channel k(21) is uncertain. Laser photolysis (Huang et al 1994) and molecular beam (Schmoltner et al 1989) experiments suggest values near 40%. However, many kinetics experiments (Peeters et al 1986, Frank et al 1986, Michael and Wagner 1990, Boullart and Peeters 1992, Peeters et al 1994) give H atom yields of up to 85%. The branching ratio k23/(k21+k23) = 0.34 is from Peeters et al.(1986) and Frank et al. (1986), and is also the same as an average of 7 studies.

In some target and validation calculations, the k23/k21 branching ratio was erroneously reversed.  Correct computations for experiments sensitive to these steps showed no significant difference.

REFERENCES:

Michael, J.V., and Wagner, A.F. (1990) J. Phys. Chem. 94, 2453.

Peeters, J., Schaekers, M., and Vinckier, C. (1986) J. Phys. Chem. 90, 6552.

Frank, P., Bhaskaran, K.A., and Just, Th. (1986) 21st Symposium (International) on Combustion, p. 885.

Peeters, J., Boullart, W., and Langhans, I. (1994) Int. J. Chem. Kinet. 26, 869.

Boullart, W., and Peeters, J. (1992) J. Phys. Chem. 96, 9810.

Schmoltner, A. M., Chu, P. M., and Lee, Y. T. (1989) J. Chem. Phys. 91, 5365.

Huang, X., Xing, G., and Bersohn, R. (1994) J. Chem. Phys. 101, 5818.

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    Temp      delta-S     delta-H      kf          kr         Keq
     (K)    (cal/mol K)  (kcal/mol) ----(mol,cm3,s)-----   
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     300         7.2       -46.7    2.59E+10    6.18E-26    4.20E+35
     500         6.5       -47.0    2.57E+11    2.70E-11    9.50E+21
    1000         4.9       -48.2    2.67E+12    9.59E+00    4.05E+11
    1500         3.8       -49.6    8.24E+12    7.37E+04    1.13E+08
    2000         2.9       -51.1    1.73E+13    1.04E+07    1.66E+06
    2500         2.2       -52.7    2.97E+13    2.42E+08    1.22E+05
    3000         1.6       -54.4    4.55E+13    2.24E+09    2.04E+04
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