Experimental and theoretical studies of the reaction of the phenyl radical with methane

Journal Article · Thu May 13 04:00:00 EDT 1999 · Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory

DOI:https://doi.org/10.1021/jp983140s· OSTI ID:351574

Tokmakov, I V; Park, J; Gheyas, S; Lin, M C ^[1]

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1. Emory Univ., Atlanta, GA (United States). Dept. of Chemistry

The kinetics of the metathetical reaction of phenyl radical with methane has been studied theoretically and experimentally. The rate constants determined by two complementary methods, pyrolysis/Fourier transform infrared spectrometry and pulsed laser photolysis/mass spectrometry in the temperature range 600--980 K, give the Arrhenius equation: k{sub 1} = 10{sup 12.78{+-}0.13} exp[({minus}6201 {+-} 225)/T] cm{sup 3}/(mol s). At the best theoretical level employed (G2M (CCMP2)), the barrier for the reaction at 0 K is E{sub 1}{sup 0} = 9.3 kcal/mol. The rate constant k{sub 1} calculated from theoretical molecular parameters fits experimental data if the barrier height is increased to 10.5 kcal/mol. The fitted barrier is well within the 1--3 kcal/mol accuracy of the G2M method for the present open-shell, seven-heavy-atom system. Because of the relatively high reaction barrier and the predicted high imaginary frequency (1551 cm{sup {minus}1}), tunneling corrections resulted in a significant enhancement in the calculated rate constant, 150% at 500 K and 7% at 2000 K. The theoretical result also correlates well with recently reported shock-tube data measured in the temperature range 1050--1450 K by UV absorption spectrometry. Kinetic analysis of the toluene formation data obtained from the photolysis of acetophenone without and with added H{sub 2} and CH{sub 4} gave the rate constant for the recombination of CH{sub 3} and C{sub 6}H{sub 5}, k{sub 2} = (1.38 {+-} 0.08) {times} 10{sup 13} exp[{minus}(23 {+-} 36)/T] cm{sup 3}/(mol s) for the temperature range 300--980 K.

• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: FG02-97ER14784
• OSTI ID: 351574
• Journal Information: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Journal Name: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory Journal Issue: 19 Vol. 103; ISSN 1089-5639; ISSN JPCAFH
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
CALCULATION METHODS
CHEMICAL REACTION KINETICS
CORRELATIONS
METHANE
PHENYL RADICALS
PHOTOLYSIS
PYROLYSIS
TEMPERATURE DEPENDENCE