Unimolecular decomposition of n-C{sub 4}H{sub 9} and iso-C{sub 4}H{sub 9} radicals
- Catholic Univ. of America, Washington, DC (United States)
The kinetics of the unimolecular decomposition of the n-C{sub 4}H{sub 9} radical has been studied experimentally in a heated tubular flow reactor coupled to a photoionization mass spectrometer. Rate constants for the decomposition were determined in time-resolved experiments as a function of temperature (560-620 K) and bath gas density ((3-18) x 10{sup 16} molecules cm{sup -3}) in two bath gases, He and N{sub 2}. The rate constants are in the falloff region under the conditions of the experiments. Structures, vibrational frequencies, and barriers for internal rotations of n-butyl and iso-butyl radicals and their decomposition transition states were obtained by ab initio calculations using UHF/6-31G{sup *} and MP2/6-31G{sup *} methods. The results of ab initio calculation, together with the reanalysis of earlier studies of the reverse reactions, were used to create transition-state models of the reactions of unimolecular decomposition of n-butyl(1) and iso-butyl (2) radicals. Falloff behavior of reaction 1 was reproduced using master equation modeling with the energy barrier height for decomposition obtained from optimization of the agreement between experimental and calculated rate constants. The values of [{Delta}]{sub all}=-28 cm{sup -1} (He) and -40 cm{sup -1}(N{sub 2}) for the average energy loss per collision were obtained using an exponential-down model. 66 refs., 5 figs., 3 tabs.
- OSTI ID:
- 227709
- Journal Information:
- Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 13 Vol. 100; ISSN JPCHAX; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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