Sucrose optical rotation

Polarization is the most common method for the determination of sugar in sugar-containing commodities as well as many foodstuffs. Polarimetry is apphed in sugar analysis based on the fact that the optical rotation of pure sucrose solutions is a linear function of the sucrose concentration of the solution. Saccharimeters are polarimeters in which the scales have been modified to read directiy in percent sucrose based on the normal sugar solution reading 100%. 

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... 

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. 

Starting with a sucrose concentration AO = 1.0 millimol/liter and an enzyme concentration Ceo = 0.01 millimol/liter, the following kinetic data are obtained in a batch reactor (concentrations calculated from optical rotation measurements) ... 

Acid Hydrolysis. Lactose is resistant to acid hydrolysis compared to other disaccharides such as sucrose. In fact, organic acids, such as citric acid, that easily hydrolyze sucrose are unable to hydrolyze lactose under the same conditions. This is useful in analyzing a mixture of these two sugars, because the quantity of sucrose can be measured by the extent of these changes in the optical rotation of reducing power as a result of mild acid hydrolysis. The speed of hydrolysis of lactose varies with time, temperature, and concentration of the reactant, as shown in Table 6.8. 

Fra. 3.—Effect of Salts on the Optical Rotation of Sucrose in Aqueous Solution.1 (Combined concentration of sucrose and salt is 1 M.)... 

Vavrinecz has shown that, the optical rotation of sucrose depends upon the concentration of both the sugar and the salt. Empirical relationships for the chlorides, bromides, iodides, and acetates of sodium and potassium were determined. 

Thomsen,133 Smolenski and Kozlowski,134 and Reeves and Blouin131 observed that sodium hydroxide has a relatively large effect on the optical rotation of sucrose. a,a-TrehaloSe,m on the other hand, is affected only slightly. Thomsen133 and Reeves and Blouin131 made no attempt to interpret the unusual behavior of sucrose Smolenski and Kozlowski,134 however, assumed that the reaction was that of alcoholate formation, and they calculated dissociation constants for sucrose. 

Fig. 2. —Changes in optical rotation, a X 50, observed during hydrolysis of 1.0% sucrose from melezitose (solid circles) and of 1.0% Bureau of Standards sucrose (open circles) by 1.0 N HC1 at 22°C. 1, 2 dm.

K. Smolenski and W. Kozlowski, Optical rotation of alkali solutions of sucrose, Roczniki Chem., 16 (1936) 270-279 Chem. Abstr., 30 (1936) 65307. 

Ex. 2 The optical rotation of sucrose in presence of dil. HCl at various intervals is given in the following table ... 

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