Specific rotation of sugars

The following Tables record the melting points and specific rotations of sugar dithioacetals and certain derivatives. 

Fig. 4 shows the maximum change in specific rotation of sugars 4-8 (under the experimental conditions) in the pH range 5.7-6.0. 

Substituent effect, additivity of, 570 electrophilic aromatic substitution and, 560-563 summary of. 569 Substitution reaction, 138 Substrate (enzyme), 1041 Succinic acid, structure of, 753 Sucralose, structure of. 1006 sweetness of, 1005 Sucrose, molecular model of. 999 specific rotation of, 296 structure of, 999 sweetness of, 1005 Sugar, complex, 974 d, 980 L, 980... 

In Table II are given the melting point, boiling point, and specific rotation of the 2,5-anhydrides of sugars, alditols, and aldonic acids that have thus far been studied. 

Problem 22.40 Hydrolysis of ( + )-sucrose gives a mixture of d-( + )-glucose ([aji, = 52.7°) and o-(-)-fructose ((ajo = -92.4°) called invert sugar. Calculate the specific rotation of invert sugar. 

Vosburgh19 gives tables of the specific rotations of aqueous solutions of fructose at different temperatures and concentrations. He deduced the following formulas 1, 2 and 3 which are useful for calculating the fructose content of invert sugar of known specific rotation ... 

In the following Tables, an attempt has been made to compile a comprehensive list of the melting points and specific rotations of 2-amino-2-deoxy sugars and their derivatives. Literature up to late 1959 has been surveyed. The tables replace those of A. B. Foster and M. Stacey, Advances in Carbohydrate Chem., 7, 281 (1952) and bring the subject up to date. 

The specific rotations of the compounds are important. The majority mutarotate in water and in alcohols, in striking contrast to the nonmutaro-tation of other sugar derivatives in which the reducing center is substituted. 

Another numerical relationship involving the optical rotations of the poly-O-acetylglycosyl halides has been deduced by Brauns, who has summarized the results obtained after many years of precise observation on carefully purified materials. Brauns has shown that, in a number of cases, the differences of the specific rotations of the acetohalogeno derivatives of a sugar are directly proportional to the differences in the atomic radii of the halogen atoms. That is, for a given sugar the differences of the specific rotations (acetochloro — acetofluoro), (acetobromo — acetochloro), (ace-... 

Interestingly enough, the hexabenzoate, although not crystalline, was very much like the compound previously described by Pictet and Chavan. The specific rotation was —125° (c 1.5, benzene) and the melting point was 116°, whereas the compound in the earlier work melted at 118° and had a specific rotation of —122.5° in benzene. It is quite probable that the formation of isomeric derivatives of di-n-fructose anhydride stems from the fact that the anhydro sugar itself is a mixture of different isomers. 

The determination of sugars by polarimetry is carried out preferably with analytically pure derivatives in higher concentration. Mono-, di-, and smaller oligosaccharides are optically active as a result of the presence of their chiral centers and rotate the plane of the polarized light. The highly specific rotation of disaccharides is dependent not only on the wavelength of the light and temperature, but also to a small extent on the concentration as shown by two common examples of simple disaccharides such as maltose and sucrose. 

Many other sugars besides glucose exhibit mutarotation. For example, u-D-galacto-pyranose has [a)i, = +150.7 , and jS-n-galactopyranose has [oJq = +52.8 . If either anomer is dissolved in water and allowed to reach equilibrium, the specific rotation of the solution is +80.2 . What are the percentages of each anomer at equilibrium Draw the pyranose forms of both anomers. 

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