Oxidation and degradation reactions

The yield (6%) of methyl /3-D-eri/product from methyl /3-D-xylopyranoside), was somewhat higher than that from chromium trioxide oxidation, but the yield was obviously limited because of secondary oxidation and degradation reactions. In unpublished experi-... 

In addition to the above mentioned oxidative deamination reactions and Garrisons cleavage of the peptide bond, oxidation and degradation reactions also take place in the remaining amino acid chains, including the benzene nucleus of Phe, as can be inferred from the presence of dialdehydes which have been found in irradiated solutions of polymyxin. As a result of these reactions the content of individual amino acids in the hydrolysates of irradiated solutions is successively lower, the decrease being largest for Phe, Leu, and for methyloctanoic acid. 

Humulone is very unstable in acidic medium and it undergoes non-controllable oxidation and degradation reactions (40,41). From the very complex reaction mixtures only compound 52 has been characterized (Fig. 28) (42). Oxidative cleavage of a 3-methyl-2-butenyl side chain has occurred in addition to intramolecular dehydration. Other components in the mixture could not be isolated. 

The most important reactions of trichloroethylene are atmospheric oxidation and degradation by aluminum chloride. Atmospheric oxidation is cataly2ed by free radicals and accelerated with heat and with light, especially ultraviolet. The addition of oxygen leads to intermediates (1) and (2). 

PVAc, PVA and PVB homopolymers as well as the different copolymers mentioned above all have a similar chemical motif in common. They exhibit an all carbon-carbon single bond backbone, which needs to be broken at some point in a potential biodegradation mechanism. With respect to the backbone, poly(vinyl ester)s are closely related to poly(olefin)s, poly(styrene)s and poly(acrylate)s. These three are known not to be biodegradable. Instead, they usually decompose by the impact of UV radiation, oxidation and hydrolysis reactions, which are not considered to be biological degradation. 

This substance undergoes degradation, oxidation, and cyclization reactions to form the first steroid "lanosterol", which is transformed into cholesterol after several steps. Schematic outlines of these biosynthetic pathways are well illustrated in the literature [56-59]. 

Mechanical components used in fuel systems such as pumps, valves, and bearings may contain copper or copper-containing alloys. As a fuel system component, copper is especially undesirable because it acts as a catalyst in promoting the oxidation of fuel paraffins to oxygen-rich, gumlike deposits. The following reaction sequence represents how copper ions can catalyze the oxidation and degradation of hydrocarbons. 

Because of the poor oxide, passivation of germanium surfaces is required for practical use of this semiconductor in devices. Although an ideally passivated surface would resist oxidation and degradation perfectly, such complete resistance is not possible in practice. For this discussion, we consider passivated surfaces as those that strengthen resistance to oxidation in both ambient air and aqueous solution. Three different surface terminating layers are reviewed sulfide-, chloride-, and hydride-terminated germanium. To date, sulfide termination creates the most ideal passivating layer, whereas both chloride and hydride termination add limited stability sufficient to alter the surface reactivity in a way that allows for further reaction. 

The oxidation and degradation of small hydrocarbon molecules have many similarities (Fig. 8.10). These reactions have been studied extensively by a variety of surface techniques such as Thermal Desorption (TDS), ion mass spectroscopy, specular infrared spectroscopy, Secondary Ion Mass Spectroscopy (SIMS), X-ray Photoelectron Spectroscopy (XPS), and so on. The reaction pathways and the final products depend on the type of oxygen-bearing species, which in turn depends on the doping and morphology of the oxide layer. This is the major reason why results obtained with different oxide sensors in different laboratories do not always agree. 

The Kochi Reaction is a one-carbon oxidative degradation of carboxylic acids, and is a valuable alternative to the Hunsdiecker Reaction. A Pb(IV) reagent is the oxidant, and this reaction is suitable for synthesis of secondary and tertiary chlorides. 

Verhaar et al.18 described the HPLC analysis of reaction mixtures of lactose (oxidation and degradation). In this work, a refractive index (RI) detector coupled with a variable wavelength ultraviolet (UV) detector at 212 nm was used to monitor the... 

Verhaar LA, Herdriks HEJ, Groeland WP, Kuster BFM. 1991. High performance liquid chromatography of reaction mixtures from the oxidation and degradation of lactose. J. Chromatogr. 549 113-125. 

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