Glucose optical rotation

The distribution between the a and p anomenc forms at equilibrium is readily cal culated from the optical rotations of the pure isomers and the final optical rotation of the solution and is determined to be 36% a to 64% p Independent measurements have established that only the pyranose forms of d glucose are present m significant quanti ties at equilibrium... 

Sucrose, in contrast, is a disaccharide of almost universal appeal and tolerance. Produced by many higher plants and commonly known as table sugar, it is one of the products of photosynthesis and is composed of fructose and glucose. Sucrose has a specific optical rotation, of +66.5°, but an... 

Per-O-acetyl dihexulose dianhydrides l3C NMR spectra, 247 H NMR spectra, 250-251 optical rotations and melting points, 244 Per-O-acetyl fructose glucose, H-NMR spectra, 252... 

Thus, if optically active substance is involved in the reaction, the change in optical rotation can be used directly to follow the progress of reaction. The inversion of sucrose in presence of HC1 giving rise to fructose and glucose can, thus, be monitored polarimetrically. 

The isomerism of a- and jS-glucose is to be attributed to the spatially different arrangement of the H and OH-groups attached to the asymmetric carbon atom 1. This atom is asymmetric in the cyclic lactol formula (Tollens). The mutarotation of the sugars, i.e. the gradual change to the final stationary value of the optical rotation, is to be explained by an equilibrium occurring in solution between the various... 

It is possible to separate the two anomeric forms of glucose by careful recrystallization from water. The two forms have different specific optical rotations (see Section 3.4.1), [aJo + 112° for a-o-glucopyranose, and [ajo + 18.7°... 

The term mutarotation means the variation of optical rotation with time, ohserved in a solution of sugar on standing. Let us have a look at this phenomenon in a glucose solution. The pure a anomer of glucose has an m.p. of 146 °C and a specific rotation [a]o +112.2°, and the specific rotation on standing is +52.6°, while pure (3 anomer has an m.p. of 148-155 °C and a specific rotation [a]D + 18.7°, and the specific rotation on standing is + 52.6°. When a sample of either pure anomer is dissolved in water, its optical rotation slowly changes and ultimately reaches a constant value of + 52.6°. Both anomers, in solution, reach an equilibrium with fixed amounts of a (35 per cent), (3 (64 per cent) and open chain ( 1 per cent) forms. 

Total hydrolysis of the polymers gave D-glucose only. Water-soluble derivatives (ethyl or carboxymethyl ethers) of the polymers were unaffected by a-amylase, but were partially hydrolyzed by a ceUulase preparation from Acdobader xylinum. The optical rotations of several preparations of this polyglucose and of cellulose (P 1150) in tetraethylammonium hydroxide were all 0°, thereby strongly suggesting that the polyglucoses are /S-D-linked.109... 

These are some examples of the use of i.r. spectra in the analysis and identification of carbohydrates in foods and natural products. Very often, these spectroscopic techniques are complementary to others, such as the study of aldobiouronic acids obtained by hydrolysis of peach-gum polysaccharides by their optical rotations and their i.r. spectra.100 However, the i.r. results appear to be sufficiently reliable to be used in the detection of traces of fructose and glucose, and to determine the d.e. (dextrose equivalent) of corn syrups, as well as the quantitative carbohydrate content in different products.101... 

Lee, Acree, and Shallenberger have in some cases carried out actual isolations of the anomeric trimethylsilyl per-O-trimethylsilyl glycosides by preparative gas chromatography and have then characterized the separated derivatives by optical rotation, elementary analysis, and NMR spectroscopy (30). These characterizations, which have been done for glucose, mannose, and galactose (see below) confirm the usefulness of the GLC technique. 

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