Halogenated carbohydrates, applications

Suppliers of visible spectrophotometers are reviewed in Table 1.1. Spectroscopic methods are applicable to the determination of phenols, chlorophenols, amines, mixtures of organics, boron, halogens, total nitrogen and total phosphorus in soils, cationic surfactants, carbohydrates, total nitrogen, phosphorus and sulphur in non-saline sediments, boron, total organic carbon, total sulphur and arsenic in saline sediments, cationic surfactants, adenosine triphosphate and total organic carbon in sludges. 

Fermentation-derived organic acids and their esters are potentially important chemical feedstocks for polymers and specialty polymers, but most significantly as alternative solvents for industrial and consumer applications. For example, lactate esters are derived from renewable carbohydrate raw materials such as cornstarch. They exhibit much lower toxicity compared with halogenated hydrocarbons and ethylene glycol ethers and are environmentally benign. Some studies suggested that lactate ester solvents have the potential of replacing petroleum-based solvents... 

This chapter deals with three important classes of biotransformations. Firstly, those enzymes that catalyse the stereoselective formation of carbon-carbon bonds will be examined. These enzymes, whose natural functions often are to degrade carbohydrate-like molecules, have proved to be versatile catalysts for C—C bond synthesis. Secondly, we shall look at those enzymes that mediate the formation of C—X bonds, where X = O, N, S, Hal (halogen). These enzymes are termed lyases (see Table 2.1) and often carry out very simple reactions (e.g. the addition of water to a double bond) with very high stereoselectivity and regioselectivity. Finally, the application of a range of enzymes (including C—C bond formation) to carbohydrate synthesis will be examined. This chapter will conclude with some examples of the ways in which multienzyme reactions can be constructed to enable highly complex molecules to be assembled in an efficient manner. 

The halogens and their oxyacids probably are the most important oxidants used in the carbohydrate field. They are widely used as bleaching agents, but the mechanism of this action remains to be clarified. As reagents for preparatory purposes (particularly for aldonic acids and lactones) and for analytical procedures, they are very important. Periodic acid, discussed in a later section, has an important application for the elucidation of structures of carbohydrates. A number of valuable commercial products are made by treatment of polysaccharides with halogens, particularly chlorine or hypochlorous acid, but the nature of these actions, such as the modification of starch, has not been clarified. 

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