Mechanisms dehydrogenation

The importance of an energized reaction complex in bimolecular reactions is illustrated by considering in more detail the termination step in the ethane dehydrogenation mechanism of Section 6.1.2 ... 

Yu, X. B. Grant, D. M. Walker, G. S., A new dehydrogenation mechanism for reversible multicomponent borohydride systems-The role of Li-Mg alloys. Chem Commun (Camb) 2006, (37), 3906-8. l0Herbstein, F. H. Averbach, B. L., The structure of lithium-magnesium solid solutions—I Measurements on the Bragg reflections. Acta Metallurgica 1956, 4, (4), 407-413. 

Application of the Structure Correspondence Principle. The kinetic parameters, z, AF°, AH°, K, and t confirm the difference in the dehydrogenation mechanism of six-membered rings over Ni on AI2O3 and over O2O3 (Table I, Nos. 1-6 and 9-18). 

The next basic aspect in the studies of dehydrogenation mechanism is the determination of the H202 interaction type with hydrocarbons. Under high-temperature oxidation conditions this interaction produces unsaturated compounds. Is this reaction the chain of a simple bimolecular type If the process is chain, variations of experimental conditions (presence of inert diluters, small additives, treatment of the reactor surface by various salts, the effect of the surfaceireaction zone volume ratio—the so-called SIV factor, etc.) must significantly change the initiation and chain termination rates. 

DEHYDROGENATION MECHANISM AND GAS-PHASE HO -DEPENDENT ELEMENTARY REACTIONS... 

Dehydrogenation Mechanism and Gas-Phase HO -Dependenl Elementary Reactions... 

J. Huot, J.F. Pelletier, L.B. Lurio, M. Sutton, R. Schulz, Investigation of dehydrogenation mechanism of MgH2-Nb nanocomposites, J. Alloys Compd. 348 (2003) 319-324. 

Moreover, we believe that the azo form helps in stabilizing several of the reactive copper complexes involved in this catalytic cycle such as the hydroxy copper complex 17. Thus, we surmise that this novel catalytic, aerobic oxidation procedure for alcohols into carbonyl derivatives proceeds via a dehydrogenation mechanism and relies on the effective role of hydrazine or azo compounds as hydrogen shuttles and stabilizing ligands for the various copper complexes (20). 

The aerobic oxidation of alcohols catalysed by low-valent late-transition-metal ions, particularly those of group VIII elements, involves an oxidative dehydrogenation mechanism. In the catalytic cycle (Fig. 5) ruthenium can form a hydridometal species by /1-hydride elimination from an alkoxymetal intermediate, which is reoxidized by dioxygen, presumably via insertion of 02 into the M-H bond with formation of H202. Alternatively, an alkoxymetal species can decompose to a proton and the reduced form of the catalyst (Fig. 5), either directly or via the intermediacy of a hydridometal intermediate. These reactions are promoted by bases as cocatalysts, which presumably facilitate the formation of an alkoxymetal intermediate and/or /1-hydride elimination. 

DEHYDROGENATION MECHANISM FROM TITANIUM-ACTIVATED SODIUM ALANATE... 

Dehydrogenation Mechanism from Titanium-Activated Sodium Alanate... 

By combining the techniques of XPS and XAS, insights into the electronic structure of the dehydrogenation catalysts V Oy/alumina have been observed, and, by correlation with activity data, a greater understanding of the dehydrogenation mechanism and subsequent coke formation, was possible. 

Pohjala, E. Indolizine derivatives. IV. Evidence for a disproportionation-dehydrogenation mechanism in the Perkin reaction of 2-pyridinecarbaldehyde in the presence of a,P-unsaturated carbonyl compounds to give 1-acylpyrrolo[2,1,5-cd]indolizines. Heterocycles 1975,3, 615-618. 

LeBlanc and Plaschke1 state that the amount of hydrogen in the gases from the reaction exceeded the sum of the carbon monoxide and carbon dioxide. This fact led them to propose the dehydrogenation mechanism. Orloff states that under favorable conditions of operation hydrogen represents 19 to 20 per cent of the gas volume, and that the proper course of the reaction could be followed by the amount of hydrogen formed. 

At this point, there is at hand for the catalyst no hydrogen capable of dehydrogenation, whereas it is available for alcohol and aldehyde (but not for acetic acid), and the catalyst assumes the potential of the remaining molecular oxj gen present. These observations support the dehydrogenation mechanism for catalytic oxidation. 

Rottenberg and Baertschi have carried out oxidation experiments in the presence of the isotope Ethanol was oxidized to acetic acid in two experiments. In the first, the oxygen used was labeled with and, in the second, the solvent water contained H20 . In the first case, only 5% of the was found in the acetic acid and, in the second, 80 to 90% of the 0 was removed from the water. Although these results could be explained by the dehydrogenation mechanism, they are not conclusive, since the isotope distribution can also be explained through isotope exchange of the intermediate acetaldehyde, as it is known that this exchange is very rapid. 

Huot, J., Pelletier, J. R, Lurio, L. B., Sutton, M. and Schulz, R. (2003a) Investigation of dehydrogenation mechanism of MgH2-Nb nanocomposites. Journal of Alloys and Compounds, 348, 319-324. 

Yu X B, Grant D M and Walker G S (2006), A new dehydrogenation mechanism for reversible multicomponent borohydride systems - the role of Li-Mg alloys, Chem. Comm., 37, 3906-3908. 

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