Hydrogenation competitive process

It was found that heating of the deuteriated bicyclodiene 111 at 110°C was accompanied by two competitive processes having comparable rates (a) butadienylcyclopropane rearrangement via a transoid transition state (111 113) and (b) enda,enda-1,5-hydrogen... 

Knowledge of the variation of electron transfer rate with electrode potential is important for the understanding of electrochemical reactions. The first experiments in this area were prompted by the observation that nitrobenzenes and aromatic carbonyl compounds are reduced in acid solution with little competition from the hydrogen evolution process. This is the case even though the electrode potential is more negative than the value calculated for the reversible evolution of hydrogen in the same solution. The kinetics of hydrogen evolution have been examined in detail. 

Often intertwined with the catalytic reduction of carbon dioxide is the reduction of protons to form hydrogen gas. This competitive process takes place because of the relatively modest cathode potential required for hydrogen evolution. Moreover, some catalysts can shift the potential needed for the evolution of hydrogen into the region of the catalytic reduction of carbon dioxide, thereby decreasing the efficiency for the desired process involving carbon dioxide. This problem was... 

It is considered in a first approach that both P° and P ° radicals are equally reactive in terminations or oxidations, so that this reaction - as hydrogen abstraction - does not modify the whole kinetics. The oxygen addition to radicals is very fast, k2 10s 109 lmoH1 s-1, so that there is practically no competitive process when 02 is in sufficient concentration to scavenge all the P° radicals. 

Solubilization of water. Detergency is defined as the ability of surfactant molecules to solubilize water molecules or polar substances in soft-core and hardcore RMs. Thus, micellization and solubilization are competitive processes. Any solubilized probe molecule causes a decrease in the CMC. Solubilization describes the dissolution of a solid, liquid or gas by an interaction with surfactant molecules. Addition of water has a dramatic effect on surfactant aggregation in hydrocarbons because hydrogen bonding has an appreciable stabilizing effect on reverse micelles. Solubilization for reverse micelles is phenomenologically similar to the adsorption processes (Eicke and Christen, 1978 Kitahara, 1980 Kitahara et al., 1976 Singleterry, 1955). 

HTGR with advanced hydrogen production processes appear to be competitive with steam methane reforming even without the added benefit of being emission-free. 

To assess the economic competitiveness of the hydrogen production processes studied, alkaline electrolysis is taken as the reference the current leading processes which use fossil fuel as reactant and heat sources are not sustainable and the unavoidable price increases in years to come aggravated by carbon taxation will inexorably drive the costs of production of these processes higher than that of alkaline electrolysis. 

In the absence of 7-hydrogen, other intramolecular hydrogen abstraction processes can become competitive. For example, a highly diastereoselective pho-tocyclization to cw-3-hydroxyproline derivatives is observed with substituted N-(2-benzoylethyl)-N-tosylglycine esters 155. The products 156-157 involve a 8-hydrogen abstraction by the excited carbonyl and a cyclization of the 1,5-biradical intermediate. In the presence of a (3-substituent, a high asymmetric induction is observed. The observed selectivity can be deduced from the preferred conforma-... 

The disproportionation of HOOH occurs via a concerted transfer of the two hydrogen atoms from a second HOOH to the Fe Cl3(HOOH) adduct. This dehydrogenation of HOOH is a competitive process with the Fe Cfi/substrate/HOOH reactions. The controlled introduction of dilute HOOH into the Fe Cfi/substrate solution limits the concentration of HOOH and ensures that the substrate/HOOH reaction can be competitive with the second-order disproportionation process. The substrate reaction efficiencies in Table 11 are proportional to the relative rates of reaction ( RH/kHoon)-The mode of activation of HOOH by Fe Cls is analogous to that of Fe (MeCN)4 + both are strong electrophiles in ligand-free dry MeCN and induce HOOH to monooxygenate organic substrates. 

Main fragmentations occurring both in the ion source, and in metastable and collision-induced dissociation (CID) experiments involve the losses of a hydrogen atom, HCN, and MeCN. These are competitive processes, whose abundances depend on the position of the nitrogen in the pyridine ring. Stable isotope labeling showed that the loss of HCN occurs from the five-membered ring (Scheme 1). 

It was suggested that the efficiency of primary step II increases with increasing number of y-hydrogen atoms present in the molecule. Nicol and Calvert pointed out that when there are different competitive processes of type II possible i.e. when both step Ila and Ilb can occur), the ratio of the amounts of the olefins formed in the competitive processes is nearly the same as that expected statistically on the basis of the number of y-hydrogen atoms available in the two alkyl groups. 

Nearly every chemical process has realistic alternative routes. Organic electrosyntheses compete with conventional —as electrochemists like to say—reactions, such as reductions, oxidations, and catalytic hydrogenations. Competition doesn t necessarily mean that the same starting material is converted into the same end product. The route to the target molecule can be totally different, starting from other precursors or following alternative reaction paths (Fig, 7),... 

It was shown that with a Pd/C catalyst in the liquid phase terminal triple bonds were saturated faster than internal ones, and both hydrogenated faster than terminal or internal double bonds in competitive processes (Eqn. 16.5). Further, alkene isomerization generally does not take place over palladium catalysts when alkynes are present. This selective hydrogenation depends on the stronger adsorption of an alkyne compared to an alkene. It is also possible that steric factors can influence the selectivity in the competitive semihydrogenation of an acetylene and an olefmic group in the same molecule. When the double bond and the triple bond are c/s to each other as in 7, selective adsorption of the acetylene... 

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