Carbohydrates with bromine

Derivatives of aldoses in which the terminal aldehyde function is oxidized to a car boxylic acid are called aldonic acids Aldonic acids are named by replacing the ose ending of the aldose by omc acid Oxidation of aldoses with bromine is the most com monly used method for the preparation of aldonic acids and involves the furanose or pyranose form of the carbohydrate... 

The survey is intended to cover the published literature on the subject as fully as possible. Although the four halogens are well known as constituents of a wide range of carbohydrate compounds, radical-mediated halogenations have, in most cases, been realized only with bromine. There are, however, some examples of chlorinations to the best of our knowledge, there are no reported fluorinations or iodinations which occur by direct, radical-mediated processes. The radical-mediated reactions by which bromodeoxy carbohydrates are obtainable from benzylidene acetals17-19 are not considered. 

Aldehydes react with NBS/AIBN to give acyl bromides721 and carbohydrates are brominated by NBS/BPO722. 

The optically inactive carbohydrate bio-inonose, QH10O5, reduces Benedict s solution, but does not react with bromine water. It is reduced to R and S, of formula C6H12O6. Compounds R and S are oxidized by HIO4 to six moles of HCOOH, and react with acetic anhydride to yield products of formula CigH240i2. Vigorous oxidation of bio-inonose yields DL-idaric acid (the dicarboxylic acid from idose) as the only six-carbon fragment. 

Mixed bishydrazones (25,26,61) of type 42 were similarly transformed into 67 upon treatment with cupric chloride (30). The bis(o-chlorophenyl) analogue of 41 gave the corresponding o-chloro derivative of 66 without loss of chlorine atoms (40), as was anticipated from previous studies in the carbohydrate series. Bromination of the bis(phenyl-hydrazone) (41) afforded the p-bromophenyl analogue (66) (62). 

Trimethyl phosphate with bromine or chlorine converts benzylidene acetals into halo benzoates similarly to A -bromosuccinimide, although the reaction has not yet been applied to carbohydrates. ... 

The most commonly used method for preparing aldonic acids is by oxidation with bromine in aqueous solution. The species that is oxidized is a furanose or pyranose form of the carbohydrate. 

RufT degradation A method for shortening the chain of an aldose by one carbon atom by treatment with bromine water, followed by hydrogen peroxide and Fe2(S04)3. (p. 1120) starches A class of a-1,4 polymers of glucose used for carbohydrate storage in plants and animals, (p. 1135)... 

When the configuration at (at least) one chiral unit is known in a nonracemic product, then the relative configuration needs to be determined. This situation occurs in substrate-induced reactions with many classical examples in steroid, terpene, and carbohydrate chemistry, such as the reduction of a carbonyl group (diastereoface-differentiating reaction), the transformation —CH2------> —CHBr— by radical bromination (diastereotopos-differentiating reaction), or dif-... 

Certain polysaccharides are normally hydrolyzed with mineral acid, usually sulfuric acid, either by direct refluxing with dilute acid or by preliminary dissolution in concentrated acid. Typical procedures have been described, and the associated problems discussed.22,23 Although prior solution of the polysaccharide in 72% sulfuric acid is a standard procedure,24 it has been shown that part of the carbohydrate may become sulfated, leading to erroneous results.23 When noncrystalline polysaccharides are being hydrolyzed, the treatment with 72% acid may be slightly modified.26 In special situations, oxidative hydrolysis, for example, of carrageenan, may be achieved by using sulfuric acid in the presence of bromine.27... 

A procedure for bromination of 2-phenyl-l,3-dioxolanes with N,N-dibromobenzenesulfonamide (C6H5S02NBr2) has been described,184 but it has not yet been applied in the carbohydrate field. The behavior of this reagent is essentially identical to that of N-bromosuccinimide, but some differences were noted, and a suggested mechanism was discussed.184... 

Some elements found in hody tissues have no apparent physiological role, hut have not been shown in he toxic. Examples arc rubidium, strontium, titanium, niobium, germanium, and lanthanum. Other elements are toxic when found in greater than trace amounts, and sometimes in trace amounts. These taller elements include arsenic, mercury, lead, cadmium, silver, zirconium, beryllium, and thallium. Numerous irlhcr elements are used in medicine in non-nulrieni roles. These include lithium, bismuth, antimony, bromine, platinum, and gold. The interactions of mineral nutrients with carbohydrates, fats, and proteins, minerals with vitamins (qv). and mineral nutrients with toxic elements are areas of active investigation. 

Radical-mediated brominations of carbohydrate derivatives have usually been conducted in refluxing carbon tetrachloride, under a tungsten (150— 250 W) or heat (250-450 W) lamp, with either JV-bromosuccinimide (1.2— 5 molar equivalents) or bromine (2-5 equivalents) as the source of halogen. Addition of bromotrichloromethane to the carbon tetrachloride can be advantageous.25 Substrate concentrations have ranged from 0.02 to 0.2 mol.l-1 and have depended to some degree on solubility factors, and ordinary laboratory glassware has most often been used. 

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