Activation parameters aldehyde oxidation

Kinetic studies were made on the cleavage of franx-cinnamate to benzoic acid by stoich. [Ru0 p7aq. 1.7M NaOH/85°C isotope effects and activation parameters were determined. Formation of an alkene-[RuO ] cyclic Ru(lV) ester (1), oxidation of this with more ruthenate to the cyclic Ru(Vl) ester (2) and oxidative decomposition of this via (3) to aldehydes R CHO and R CHO was suggested. The aldehydes are subsequently oxidised to R COOH and R COOH by more [RuO ] (not shown in the Scheme) (Fig. 1.16) [349, 350],... 

The kinetics of the oxidation of aromatic aldehydes by A-chloronicotinamide in aqueous acetic acid are first order in both reactants and in proton.339 The effect of substituents has been studied, and data at different temperatures yield activation parameters. 

The oxalic acid-catalysed oxidation of Af,a-diphenylnitrones by imidazolium dichromate (IDC) is first order in the nitrone, IDC, and oxalic acid. A positive fractional order was obtained with respect to acidity. A mechanism involving the protonated nitrone as a reactive species has been proposed. Oxidation of substituted phenols with isonico-tinium dichromate in the presence of oxalic acid is first order in the reductant and oxidant but showed a fractional order in oxalic acid the Hammett plot is downward concave. Activation parameters have been determined and a mechanism has been proposed. The oxidation of some secondary alcohols," aliphatic aldehydes, and three lower oxyacids of... 

Hundreds of substances of many types have been tested as dehydration catalysts and found active. Lists can be found in the literature [69,76,85] and we need to name here only such catalysts which show high activity and selectivity. The latter parameter is more important because a number of solids, especially oxides, can catalyse both the dehydration and the dehydrogenation of alcohols. The formation of aldehydes or ketones is then a parallel reaction to the dehydration, and the ratio of the rates depends on the nature of the catalyst. Only few oxides are clean dehydration or dehydrogeneration catalysts, but the selectivity may be shifted to some extent in either direction by the method of catalyst preparation. 

The aim of this work was to develop and present a new method for the synthes selective platinum catalysts for the hydrogenation of unsaturated aldehydes to unsatui alcohols. The method of preparation presented above makes it possible to obtain cata possessing polar platinum surface, due to the presence of active centers near the intei metal - partially reduced transition metal oxide. This transition metal oxide adsorb carbonyl oxygen atom whereas adjacent platinum atom interacts with carbonyl ca atom. In such a situation, the C=C bond is quite far from the surface so its adsorption i favored. There are also some additional parameters which should be taken consideration. The first is the size of platinum crystallites located on the catalyst sur Large platinum crystallites cause planar adsorption of aldehyde molecule in such adsorption of both double bonds is highly probable. It is known that a more sur... 

The transfer and the adsorption are strongly influenced by the size of the compound (surface and volume) and by the functional groups present in the molecule (alcohols, aldehydes, ketones, carboxylic acids, amines, mercaptans, halogenated molecules) inducing some polarization effects. Some studies have reported a quantitative structure activity relationship (QSAR) between molecular structure and adsorption parameters (adsorption capacities, energies) [32,37,78]. The reactivity of some compounds leads to oxidation at the adsorbent surface, which plays a catalytic role. Moreover, a mixture of molecules in air... 

Table I compares glucose with ascorbic acid for a number of oxidative parameters. The higher rate of oxidation, oxidant production, and concomitant protein fragmentation and generation of fluorescence products on albumin by ascorbic acid is also accompanied by aldehyde products able to bind to proteins (Kurata et al, 1973 Kurata and Fujimaki, 1976). The attachment of carbohydrate to albumin (Hunt and Wolff, 1991b) may explain ascorbic acid s ability to inhibit the oxidation of LDL by copper in vitro (Retsky et al., 1993 Jialal et al, 1990). A number of studies have shown that ascorbic acid can decrease the oxidation of LDL by copper, the process usually occurring over several hours. Such observations are not indicative of an antioxidant activity.

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