Maltose specific rotation

Tables II-XV constitute a list of most of the known, characterized derivatives of maltose. The names of the solvents used for measuring the specific rotations are abbreviated as follows A, acetone B, benzene C, chloroform E, ethanol M, methanol P, pyridine and W, water.

The specific rotation of maltose in water is +138°. What would be the concentration of a maltose solution that had an optical rotation of +23° if a polarimeter tube 10 cm long was used ... 

The specific rotation of the limit dextrins is lower than that calculated under the assumption that only maltose linkages occur. Maltotriose should have [a]u about -f 153°. 

The problem of the acid-catalyzed hydrolysis of the carbohydrate orthoesters was brought nearer to the final solution by Pacsu s experiments on the hydrolysis of maltose methyl 1,2-orthoacetate. Since two adjacent hydroxyl groups on the same side of the plane are necessary for the formation of orthoester derivatives, the maltose methyl orthoacetate must have an -configuration. Hydrolytic experiments with very dilute hydrochloric acid confirmed this. Two consecutive reactions took place at a pH of 4. In the first reaction, the original specific rotation, Co ]d - -103.7 in pure water, increased to -1-134.6° within two minutes. The latter figure corresponds to the specific rotation of a-maltose 2-acetate. The second reaction k = 0.0095) corresponded to the downward muta-rotation of a-maltose 2-acetate. When the hydrogen-ion concentration,... 

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. 

PROBLEM 16.13 When crystalline maltose is dissolved in water, the initial specific rotation changes and gradually reaches an equilibrium value. Explain. 

Later, Machell and Richards and Whistler and BeMiller isolated the compound as a sirup (in yields of about 1%) by treatment of maltose with 0.05 N sodium hydroxide and of cellobiose with 0.05 N potassium hydroxide. There was a divergence in the reported specific optical rotations (in water), namely, —24.1° and -fll°, respectively, which might be attributable to degradation of this labile compound during isolation or storage. The crystalline (2,4-dinitrophenyl)osazone prepared in both investigations was further characterized as its crystalline triacetate. ... 

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