Carboxylic acids aldehydes, degradation with

The reaction of carboxylic acids, aldehydes or ketones with hydrazoic acid in the presence of a strong acid is known as the Schmidt reaction A common application is the conversion of a carboxylic acid 1 into an amine 2 with concomitant chain degradation by one carbon atom. The reaction of hydrazoic acid with a ketone 3 does not lead to chain degradation, but rather to formation of an amide 4 by formal insertion of an NH-group. 

As for reaction of wood with carboxylic acids, the reaction of aldehydes also requires the use of an acid catalyst, which leads to degradation of the substrate. The most studied reaction in this category is that of formaldehyde with wood (Figure 4.10). 

Alcohols are oxidized to aldehydes by the liver enzyme alcohol dehydrogenase, and aldehydes to carboxylic acids by aldehyde dehydrogenase. In mammals, monooxygenases can be induced by plant secondary metabolites such as a-pinene, caffeine, or isobornyl acetate. Reduction is less common and plays a role with ketones that cannot be further oxidized. Hydrolysis, the degradation of a compound with addition of water, is also less common than oxidation. 

Lysine is not only a constituent of proteins. It can also be trimethylated and converted to carnitine (p. 944). In mammals some specific lysyl side chains of proteins undergo N-trimethylation and proteolytic degradation with release of free trimethyllysine (Eq. 24-30) 278/279 The free trimethyllysine then undergoes hydroxylation by a 2-oxoglutarate-Fe2+-ascorbate-dependent hydroxylase (Eq. 18-51) to form P-hydroxytrimethyllysine, which is cleaved by a PLP-dependent enzyme (Chapter 14). The resulting aldehyde is oxidized to the carboxylic acid and is converted by a second 2-oxoglutarate-Fe2+-ascorbate-dependent hydroxylase to carnitine (Eq. 24-30 see also Eq. 18-50). 

Aldoses can be degraded by the following two reactions. First the aldehyde is oxidized with bromine water to form a carboxylic acid. Next the carboxylic acid is decarboxy-lated with hydrogen peroxide and ferric sulfate leaving an aldehyde. The new aldose is one carbon shorter. When glucose is degraded in this manner, and the product is oxidized by dilute nitric acid, an optically active compound is formed. 

An antennal-specific aldehyde oxidase (AOX) of M. sexta (MsexAOX) was the next identified pheromone-degrading enzyme (Rybczynski el al., 1989). The activity of MsexAOX was visualized on non-denaturing PAGE, and was shown to be antennal specific but present in sensilla of both male and female antennae. MsexAOX was observed as a dimer with a combined estimated molecular mass of 295 kDa. M. sexta uses a multicomponent pheromone consisting exclusively of aldehydes including bombykal (Starratt el al., 1979 Tumlinson el al., 1989, 1994) MsexAOX was shown to degrade bombykal to its carboxylic acid. Both TLC and spectrophotometric assays were established and a variety of substrates and inhibitors were characterized. Making adjustments for the concentrations and volumes within a sensillum lumen, the in vivo half-life of pheromone was estimated at 0.6 msec in the presence of this enzyme (Rybczynski el al., 1989). 

The overwhelming majority of alcohol oxidations (including those of carbohydrates) have been run in SSE s of relatively high water contents, often with strong acid present, under constant current conditions 123 Selective oxidation of an alcohol to an aldehyde cannot be accomplished under such conditions instead the carboxylic acid and its degradation product is formed. The cpe approach in SSE s of low water contents should no doubt pay rich devidends in this area. The same applies to the oxidation of secondary alcohols, in which the acid SSE s previously used seem to promote anodic degradation of the ketone formed. 

To ensure complete oxidation of aldehydes to carboxylic acids, Aulin-Erdtman and Tomita (1963) treated the ozonation products of lignin model compounds with hydrogen peroxide. Soteland (1971) applied hydrogen peroxide to a groundwood ozonation product and found that it degraded the components to unidentified volatile substances. To simplify the product mixture, reduction is sometimes used to stop further oxidation. Tanahashi et al. (1975) applied palladium-catalyzed hydrogenation, while Kondo et al. (1987) added dimethyl sulfide. 

If the carboxylic acids on the cellulosic chain are not the major cause of the thermooxidative decay of old cellulosic textiles, one must consider the carbonyl species, particularly the aldehydes on the C2 and Q) carbons. Nikitin (14) noted that the primary autoxidation process is a reaction of molecular oxygen with aldehyde groups, which initiates a chain reaction resulting in more profound changes and decomposition of the molecule . Thus, reduction of the aldehyde groups should lead to improved stability of degraded cellulose. 

Sodium hypochlorite is used for the epoxidation of double bonds [659, 691] for the oxidation of primary alcohols to aldehydes [692], of secondary alcohols to ketones [693], and of primary amines to carbonyl compounds [692] for the conversion of benzylic halides into acids or ketones [690] for the oxidation of aromatic rings to quinones [694] and of sulfides to sulfones [695] and, especially, for the degradation of methyl ketones to carboxylic acids with one less carbon atom [655, 696, 697, 695, 699] and of a-amino acids to aldehydes with one less carbon [700]. Sodium hypochlorite is also used for the reoxidation of low-valence ruthenium compounds to ruthenium tetroxide in oxidations by ruthenium trichloride [701]. 

Degradative oxidation of unsaturated carboxylic acids leads either to aldehydes or to dicarboxylic acids. In the presence of sodium carbonate and benzene, o-nitrocinnamic acid is oxidized with potassium permanganate at 10 °C to o-nitrobenzaldehyde in 64% isolated yield [842]. 

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