Groups to carboxylic acid

Scheme 12.22 provides some examples of the oxidation of aromatic alkyl substituents to carboxylic acid groups. Entries 1 to 3 are typical oxidations of aromatic methyl groups to carboxylic acids. Entries 4 and 5 bring the carbon adjacent to the aromatic ring to the carbonyl oxidation level. 

Notably, nitrile-degrading enzymes (e.g. nitrilase that converts the CN group to carboxylic acid, and nitrile hydratase that produces an amide function) have been described, and they co-exist with aldoxime-degrading enzymes in bacteria (Reference 111 and references cited therein). Smdies in this area led to the proposal that the aldoxime-nitrile pathway, which is implemented in synthesis of drugs and fine chemicals, occurs as a natural enzymic pathway. It is of interest that the enzyme responsible for bacterial conversion of Af-hydroxy-L-phenylalanine to phenacetylaldoxime, an oxidative decarboxylation reaction, lacks heme or flavin groups which are found in plant or human enzymes that catalyze the same reaction. Its dependency on pyridoxal phosphate raised the possibility that similar systems may also be present in plants . 

By polymerization of mixtures of monomers of ethylene and the acid in a tubular reactor, and hydrolysis of copolymers of ethylene and alkyl acrylates, which converts the ester groups to carboxylic acid groups. 

This sequence of reactions is incompletely understood but involves numerous oxidations of carbon groups, for example, the conversion of methyl groups to carboxylic acids, followed by decarboxylation. The end product, cholesterol, is the precursor to cholesterol esters in the liver and is transported to the peripheral tissues where it is a precursor to membranes (all cells), bile salts (liver), steroid hormones (adrenals and reproductive tissues), and vitamin D (skin, then liver, and finally kidney). 

Animals. In rats, the major metabolic routes for pendimethalin involve hydroxylation of the 4-methyl and AM-ethyl groups, oxidation of these alkyl groups to carboxylic acids, nitro-reduction, cyclisation and conjugation (J. Zulian, J. Agric. Food Chem., 1990, 38, 1743)... 

Selective Oxidation of Hydroxymethyl Groups. Platinum on charcoal in the presence of air is the conventional method for selectively oxidising hydroxymethyl groups to carboxylic acids, and thus hexoses to uronic acids anomeric protection is required, however, and the mechanism of this heterogeneous reaction is unknown. The reaction fails with polymers, probably for... 

TEMPO-mediated reactions of solid polysaccharides, such as rayon (cellulose II) also result in clean conversion of C6 hydroxymethyl groups to carboxylic acids. ... 

The reagent, used in conjunction with sodium periodate, oxidizes phenyl groups to carboxylic acids 30... 

Methyl Groups to Aldehydes 444 ArMe -> ArCHO Methyl Groups to Carboxylic Acids 415,424 ArMe - ArC02H... 

It s not a big deal, but use of NaOH, H2O in (b) and (c) would hydrolyze the ester groups to carboxylic acids (—CO2H). Using NaOR, ROH where R corresponds to the alkyl group of the ester, prevents this (Chapter 20). 

Beside,s the A-methyl group, alkyl substituents in other parts of CM molecules can also be hydroxylated. For example, the alkyl chain in chiorpropham can be hydroxylated and then further carboxyiated (Bobtk el al 1972). The alkyl side chain on aromatic rings of CMs, such as mctol-carb and butacarb, can also be hydroxylated (Kuhr and Dorough, 1976b Kulkarni and Hodgson, 1980). Further oxidation of the hydroxylated methyl groups to carboxylic acids is also observed (Fig. 5). 

Definition Collagen which has been deamidated to modify amide groups to carboxylic acid groups Uses Film-former in cosmetics, providing skin elasticity and moisturizing props, to skin care prods. 

Base hydrolysis describes the process of heating a polymer solution with a pH above 10 to temperatures of 40 to 70 C to convert amide groups to carboxylic acid groups. 

Heating the a-substituted malonic ester in an acidic aqueous solution hydrolyzes both ester groups to carboxylic acid groups, forming an a-substituted malonic acid. 

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