Uronates

Uronic acids occupy an oxidation state between aldonic and aldanc acids They have an aldehyde function at one end of their carbon chain and a carboxyhc acid group at the other... 

Uronic acids are biosynthetic intermediates m various metabolic processes ascorbic acid (vitamin C) for example is biosynthesized by way of glucuronic acid Many metabolic waste products are excreted m the urine as their glucuronate salts... 

Uron Resins. In the textile industry, the term uron resin usually refers to the mixture of a minor amount of melamine resin and so-called uron, which in turn is predorninantly N,]S -bis(methoxymethyl)uron [7388-44-5] plus 15—25% methylated urea—formaldehyde resins, a by-product. 

N,]S7-bis(methoxymethyl)uron was first isolated and described in 1936 (41), but was commercialized only in 1960. It is manufactured (42) by the reaction of 4 mol of formaldehyde with 1 mol of urea at 60°C under highly alkaline conditions to form tetramethylolurea [2787-01-1]. After concentration under reduced pressure to remove water, excess methanol is charged and the reaction continued under acidic conditions at ambient temperatures to close the ring and methylate the hydroxymethyl groups. After filtration to remove the precipitated salts, the methanolic solution is concentrated to recover excess methanol. The product (75—85% pure) is then mixed with a methylated melamine—formaldehyde resin to reduce fabric strength losses in the presence of chlorine, and diluted with water to 50—75% soHds. Uron resins do not find significant use today due to the greater amounts of formaldehyde released from fabric treated with these resins. 

There was a tendency to use these resins mixed with urea—formaldehyde or melamine-type resins. Preparation of pure tria2ones or uron resins is difficult and expensive (61,62). Furthermore, the basic nature of the amine nitrogen in tria2one permits the use of mixtures of tria2ones with other agents to yield finishes that retain strength in hypochlorite bleaching. 

HemiceUulose is a mixture of amorphous branched-chain polysaccharides consisting of a few hundred sugar residues. They are easily hydrolyzed to monomeric sugars and uronic and acetic acids. Many different hemiceUuloses have been isolated from wood. 

Scientific name/Common name Glucan Xylan Galactan Arabinan Man nan Uronic anhydride Acetyl Lignin Ash... 

Octosyl Acids. Three octosyl uronic acid nucleosides, produced by S. cacaoi sub sp. asoensis are shown in Figure 3. The biosynthesis of (172) and (173) has been reported (1). The replacement of the pyrimidine chromophore of (171) with adenine results in a nucleoside analogue that is a competitive inhibitor of cAMP. 

Uronic acids are monosaccharides in which the terminal primary alcohol group is oxidized to a carboxyhc acid functional group, eg, D-glucuronic acid [6556-12-3] (11). 

The L-arabino-(4-0-methyl-D-glucurono)xylans are found in softwoods and annual plants. The L-arabinose is present primarily as a-L-arabinofuranosyl units, although P-L-arabinopyranosyl units may also be present. In either case, the arabinosyl units are often, but not always, present as single-unit side chains, as are the uronic acid units. 

From the presence of uronic acid, sulfate half-ester, pymvyl cycUc acetal, or succinate half-ester groups. 

Ion Exchange. Acidic polysaccharides containing uronic acids, sulfate, or phosphate groups are cation exchangers, binding metal ions. The... 

Phenylurea herbicides (urons). Dinocap, Dinoseb, Benomyl, Carbendazim and Metamitron in Waters [e.g. determination of phenylurea herbicides by reverse phase HPLC, phenylurea herbicides by dichloromethane extraction, determination by GC/NPD, phenylurea herbicides by thermospray LC-MS, Dinocap by HPLC, Dinoseb water by HPLC, Carbendazim and Benomyl (as Carbendazim) by HPLC], 1994... 

In the literature, various other types of resin preparation procedures are described, e.g. yielding uron structures [20-22] or triazinone rings in the resins [23,24]. The last ones are formed by the reaction of urea and an excess of formaldehyde under basic conditions in the presence of ammonia or an amine, respectively. These resins are used to enhance the wet strength of paper. 

Uronic acid Class of aeidie eompounds of the general formula HOOC(CHOH) CHO that eontain both earboxylie and aldehydie groups, are oxidation produets of sugars, and oeeur in many polysaeeharides espeeially in the hemieelluloses. 

Monosaccharides can be oxidized enzymatically at C-6, yielding uronic acids, such as D-glucuronic and L-iduronic acids (Figure 7.10). L-Iduronic acid is similar to D-glucuronic acid, except for having an opposite configuration at C-5. Oxidation at both C-1 and C-6 produces aldaric acids, such as D-glucaric... 

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