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Author(s):   Bohn, B.; Zetzsch, C.;
Title:   Kinetics and mechanism of the reaction of OH with the trimethylbenzenes - experimental evidence for the formation of adduct isomers
Journal:   Phys. Chem. Chem. Phys.
Volume:   14
Page(s):   13933 - 13948
Year:   2012
Reference type:   Journal article
Squib:   2012BOH/ZET13933-13948

Reaction:   1,2,4-Trimethylbenzene + ·OH → Products
Reaction order:   2
Temperature:   275 - 340 K
Pressure:  0.38 - 0.75 bar
Rate expression:   2.73x10-12 [cm3/molecule s] e6070 [±582 J/mole]/RT
Category:  Experiment
Data type:   Derived from fitting to a complex mechanism
Pressure dependence:   Rate constant is pressure independent
Experimental procedure:   Static or low flow - Data taken vs time
Excitation technique:   Flash photolysis (laser or conventional)
Time resolution:   In real time
Analytical technique:   Resonance fluorescence
Comments:   The reversible gas-phase addition of OH radicals to the trimethylbenzenes was investigated in pulsed experiments utilizing VUV flash-photolysis and resonance-fluorescence. Triexponential OH decays were observed in the presence of the trimethylbenzenes, indicating the participation of more than one adduct species. Analytical solutions for the system of differential equations with two adduct isomers were derived, and the OH decay curves were evaluated based on this reaction model. Based on literature data, the more and less stable adducts were assigned to ipso- and ortho-adduct isomers, respectively. The potential isomerization precluded the determination of primary yields of adduct isomers but formation of the ipso-adduct in any case is a minor process.

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Rate constant values calculated from the Arrhenius expression:

T (K)k(T) [cm3/molecule s]
275 3.88E-11
300 3.11E-11
325 2.58E-11
340 2.34E-11