Temperature Dependences for the Reactions of Ar+, O2+, and C7H7+ with Toluene and Ethylbenzene
AIR FORCE RESEARCH LAB KIRTLAND AFB NM SPACE VEHICLES DIRECTORATE
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We have studied the reactions of Ar, O-2, and C2H2 with toluene CH3-C6H5 and ethylbenzene C2H5-C6H5 as a function of temperature. Ar reacts with C7H8 at the collision rate constant at both 300 and 500 K to produce mainly C7H7 cations similar to 85, with the remainder of the reactivity divided into numerous small channels. The fraction of C7H7 produced as benzylium 6 membered ring, Bz as opposed to tropylium 7 membered ring, Tr is determined through ion-molecule reactivity to be primarily Bz. The reaction of Ar with C8H10 proceeds at slightly lower than the collision rate constant at 300 K, but increases to the collision rate constant at 500 K. Over 80 of the products were C7H7, the large majority of which also is Bz. The O-2 reaction with C8H10 proceeds at the collision rate constant and produces C8H10, C6H6, and C7H7, with the latter again primarily being Bz. C7H7 was found to react with both CH3-C6H5 and C2H5-C6H5 by both collisionally stabilized clustering and a bimolecular reaction forming R-C6H4-CH2. At 300 K the rate constants are about half of the collision rate constant and drop rapidly with temperature. About 23 of the products are clusters at 300 K, 13 at 400 K, and negligible amounts at 500 and 600 K. Evidence for thermal dissociation of the cluster is presented. Calculations show the most stable structure is the one where the methylene group of benzylium is coordinated at the para position of the alkylbenzene, with one phenyl group approximately 45 degrees out of plane relative to the other. A bond strength of 15-16 kcal mol-1 is calculated for both neutrals. Numerous less stable structures were found.
- Physical Chemistry
- Atomic and Molecular Physics and Spectroscopy