Different product distributions in the

Kinetic expressions similar to that of Equation 3 and similar activation energies have been reported for methanation over a cobalt-alumina catalyst (4) and for Fischer-Tropsch reaction over a cobalt-thoria catalyst (5). This similarity, despite appreciably different product distributions in the three cases, argues for a common rate-controlling step in the mechanisms. 

Below 388 K, two different product distributions in the ammonia oxidation are observed, depending on the surface coverage. At low coverage (catalyst is active), N2 and H2O are selectively produced via stripping of hydrogen from ammonia by oxygen atoms. Moreover, the recombination of OH(a)... 

The rate was enhanced up to 2.6-fold for reaction of the 2-isomer and up to 14-fold for the 4-isomer. The product distribution in the final reaction mixtures was always somewhat different when microwave heating was used. The results were explained in terms of efficient interaction of microwaves with a highly polarized reagent molecule adsorbed on the acidic active site. Possible superheating of the active sites was difficult to detect (Sect. 10.3.3). 

This paper summarized our current understanding of the factors that determine selectivity for dehydrogenation versus formation of oxygen-containing products in the oxidation of light alkanes. From the patterns of product distribution in the oxidation of C2 to C6 alkanes obtained with supported vanadium oxide, orthovanadates of cations of different reduction potentials, and vanadates of different bonding units of VO in the active sites, it was shown that the selectivities can be explained by the probability of the surface alkyl species (or the... 

Explain why the product distribution in the chlorination of propane by sulfuryl chloride is expected to differ according to whether the hydrogen-abstraction step is accomplished by Cl- or -S02CI. 

The widely differing product distributions frorn the two anhydrides reflect the difference in structure and reactivity of the two naphthalynes. 2-3-Naphthalyne (14) behaves like benzyne, giving anthracene by 1,2-and 1,4-addition, and phenylnaphthalene by insertion, as well as some binaphthylene (15) by dimerization ... 

Table 7.3 Product distribution in the presence of different zeolites with nearly similar Brpnsted acidity...

With thermal systems either in the gas phase or in solution, it is in ter -molecular isotope effects which are more commonly studied. Intramolecular isotope effects involve distinguishing and measuring two, or more, chemically identical but isotopically different products produced in the same reaction vessel from the same reactant. The situation is different in mass spectrometry. Intramolecular isotope effects are conveniently studied, because the chemically identical products are naturally separated according to their masses. Intermolecular isotope effects on ion abundances are also easily measured, but, as regards kinetics and mechanism of reaction, their value is limited. Whereas an intramolecular isotope effect (on ion abundances) reflects kinetic isotope effects, an intermolecular isotope effect (on ion abundances) reflects kinetic isotope effects, isotope effects on the internal energy distribution, P(E), and other factors as well and the effects cannot be easily separated (vide infra). 

Table 10. Product distribution in the reaction of 70 with various aminium salts of different oxidation strength in acetonitrile/methanol 9 1 [170]...

PRODUCT DISTRIBUTION IN THE DECOMPOSITION OF PROPIONALDEHYDE AT 200 TORR INITIAL PRESSURE AND DIFFERENT TEMPERATURES (15 % CONVERSION)... 

It is well known that the product distribution also depends on the electrode material used [13, 14]. We have examined the effect of various electrode materials on the product distribution in the CO -methanol system. The current efficiencies of the reduction products are shown in Figure 6. The production of formate was fairly favorable at all electrodes, in comparison with that in aqueous systems. For example, the production of formate was more than 20% on Pt and Ni electrodes, which is much higher than that observed in aqueous systems [14]. At the metals Sn and Sb, formate production was favoured, as in the aqueous systems, but CO formation was also somewhat favored. This is due to the effect of supporting electrolyte. The electrodes Ag, Zn and Pd showed similar activities for CO production, as in aqueous systems. The efficiency of hydrocarbon formation at the Cu electrode was found to be lower, whereas that at the Ni electrode was found to be higher than that in aqueous systems. The balance of hydrogen and carbon atom concentrations on the electrode surface may explain this difference. 

A similar procedure with bis(t/ -allyl)palladium or bis(cycloocta-l,5-diene)palladium as catalyst leads to only slightly different product distributions of the tetramers. The absolute yield of the nonpolymeric products is lower in both cases. ... 

First, the product distribution in the pyrolysis of bulk nickel formate was studied at different temperatures, both with the reaction gas remaining in contact with the decomposing product, and with the reaction gas rapidly drawn off. 

A series of systematic studies on hydrolysis per se were undertaken by Sayer, Whalen, Islam, Jerina and others [147-150], The thrust of their research has been to identify the stereoelectronic, conformational and other incidental factors affecting the kinetics and product distribution in the solvolysis of various PAHDE s under diverse reaction conditions. The aim is, of course, elucidation of reaction mechanisms of PAHDE s in biological systems. Geacintov et al have conducted detailed investigations of reactions of BaPDE s with aqueous solutions of double stranded DNA as a function of temperature, pH and NaCl concentration at different levels of DNA contents [151]. 

As already pointed out (9), the stereoselectivity of the reactive intermediate should be altered if a bulky sensitizer were attached to the oxygen, but no differences in stereoselectivity between photosensitized and chemical oxygenation were observed (9). The results in Table IV provide further strong evidence that no diflFerences in stereoselectivity exist since the product distributions in the two reactions are identical with these acceptors also. 

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