Toluene, hydrogenation kinetic parameters

Non-catalytic thermal decarbonylation of quinones proceeded for 9,10-anthraquinone (ANQ), 9,10-phenanthrenequinone (PHQ), 1,4-and 1,2-naphthoquinone(NPQ) and p-benzoquinone (BNQ) in the presence of atmospheric hydrogen at 500- 600 C. ANQ or PHQ decar-bonylated in the presence of hydrogen to form fluorenone (FLR) at the first step, followed by successive hydrodecarbonylation and hydrocracking to form biphenyl and benzene. In the case of 1,4-NPQ, the reaction did not proceed in any obvious stoichiometric relation. Only 60- 70 % of 1,4-NPQ decarbonylated and was hydrogenated yielding styrene, ethylbenzene, toluene, benzene and lower hydrocarbons the remainder polymerized or partly polycondensed. Similar, or less selective results were obtained for 1,2-NPQ and p-BNQ. Analyses of kinetic treatments are reported for the consecutive reaction schemes of ANQ or PHQ as well as of FLR. The kinetic parameters for decarbonylation, polymerization, polycondensation reactions of quinones are discussed. 

As well as conventional kinetic methods, the shock-tube method and the toluene vapour-flow method have also been used for studying the unimolecular elimination of hydrogen iodide from alkyl iodides. Table 12 summarises Arrhenius Parameters for these reactions. 

The kinetics of the hydrogenation of benzene will depend on physical as well as on chemical parameters. Using toluene instead of benzene will change these physical and chemical parameters, but the reaction mechanism remains virtually the same. When no salt is added only chemical parameters influence the reaction rate. Experiments show that the initial reaction rate of the hydrogenation of benzene and of toluene, without adding salt, are approximately 8 mmol/s. 

Kinetic data for an a-hydrogen abstraction are provided very appropriately by Pedersen and Schrock. [W(NPh)(CH2SiMe3)4] decomposes thermally in toluene to give an alkylidene, as opposed to a ring, reaction (88). The activation parameters, AH = 22 kcal moP and AS = -8 cal K mol , are not dissimilar to those observed for the thorium system in Section 11.3.17. 

The kinetics of H2-dissociation was studied for the complexes [IrH(H2)X2(PR3)2l (X = C1, Br PR3 = PCya, PPds) obtained by direct hydrogenation of [IrHX2(PR3)2l in toluene- /g. VT relaxation NMR measurements allowed for the evaluation of the thermodynamic parameters associated to the H2-dissociation from both cis- and trans-[IrH(H2)X2(PR3)2l isomers suggesting that the H2-I0SS is strictly depending on the elongation of the H-H bond in the non-classical complex. 

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