Kinetics of C{sub 6}H{sub 5} radical reactions with toluene and xylenes by cavity ringdown spectrometry

Journal Article · Thu May 20 04:00:00 EDT 1999 · Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory

DOI:https://doi.org/10.1021/jp990049v· OSTI ID:351591

Park, J; Chakraborty, D; Bhusari, D M; Lin, M C ^[1]

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

The kinetics of aromatic radical reactions are relevant to the fundamental combustion chemistry of fossil fuels as well as to soot formation at its incipient stage. The kinetics for the metathetical reactions of phenyl radical with toluene and xylenes have been studied experimentally and theoretically. The absolute bimolecular rate constants for the reactions of C{sub 6}H{sub 5} with toluenes (C{sub 7}H{sub 8} and C{sub 7}D{sub 8}) and xylenes (three C{sub 8}H{sub 10} isomers) were measured by cavity ringdown spectrometry at temperatures between 295 and 483 K. Of the reaction with toluene, a strong isotope effect was observed, whereas for xylene reactions no structural preference was noticed among the three isomers. The weighted least-squares analysis of each reaction gave rise to the following rate constant expressions in units of cm{sup 3}/(mol s): k(C{sub 7}H{sub 8}) = (2.08 {+-} 0.11) {times} 10{sup 11} exp[{minus}(1027 {+-} 35)/T]; k(C{sub 7}D{sub 8}) = (2.27 {+-} 0.43) {times} 10{sup 11} exp[{minus}(1340 {+-} 64)/T]; k(C{sub 8}H{sub 10}) = (1.48 {+-} 0.11) {times} 10{sup 11} exp[{minus}(526 {+-} 27)/T]. Additionally, the authors have carried out hybrid density functional theory (B3LYP) calculations for the reactions of C{sub 7}H{sub 8} and C{sub 7}D{sub 8} using the 6-31G-(d,p) basis set. The predicted rate constants using the conventional transition state theory with the calculated vibrational frequencies and moments of inertia fit well to the experimental results with only minor adjustments in the calculated reaction barriers. Combination of their low-temperature C{sub 7}H{sub 8} kinetic data with those obtained at high temperatures in shock waves gave the expression k(C{sub 7}H{sub 8}) = (4.15 {times} 10{sup {minus}3})T{sup 4.5} exp(800/T) cm{sup 3}/(mol s) for the temperature range 300--1450 K.

• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: FG02-97ER14784
• OSTI ID: 351591
• 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: 20 Vol. 103; ISSN 1089-5639; ISSN JPCAFH
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
02 PETROLEUM
CHEMICAL REACTION YIELD
COAL
COMBUSTION KINETICS
EXPERIMENTAL DATA
PETROLEUM
PHENYL RADICALS
POTENTIAL ENERGY
SOOT
THEORETICAL DATA
TOLUENE
XYLENES