Rotation of sucrose

Problem 1.7 The specific rotation of sucrose in presence of hydrochloric acid at 35°C was measured and is given as follows ... 

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. 

Specific Rotations of Sucrose and of D-Fructoae in 4 Jlf Solutions of Alkali Metal... 

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. 

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

Example The optical rotations of sucrose in 0.5 M HC1 at 35 C at various time intervals are given below. Show that the reaction is first-order ... 

Inversion Acid- or enzyme-driven decrease in the specific rotation of sucrose, giving a mixture called invert sugar. 

The observed rotation for 100 mL of an aqueous solution containing 1 g of sucrose (ordinary sugar), placed in a 2-decimeter sample tube, is +1.33° at 25°C (using a sodium lamp). Calculate and express the specific rotation of sucrose. 

For each of the following questions, assume that all measurements are made in 10-cm polarimeter sample containers. (a) A 10-mL solution of 0.4 g of optically active 2-butanol in water displays an optical rotation of —0.56°. What is its specific rotation (b) The specific rotation of sucrose (common sugar) is +66.4. What would be the observed optical rotation of such a solution containing 3 g of sucrose (c) A solution of pure (5)-2-bromobutane in ethanol is found to have an observed a = 57.3°. If [a] for (S)-2-bromobutane is 23.1, what is the concentration of the solution ... 

Sucrose is dextro-rotatory. Fructose shows a laevo-rotation greater in magnitude than the dextro-rotation shown by glucose. Hence as the hydrolysis of sucrose proceeds, the dextro-rotation gradually falls to zero and the solution finally shows a laevo-rotation. This hydrolysis is therefore sometimes called inversion and so the enzyme which catalyses the reaction is known as " invertase. Its more systematic name is, however, sucrase. 

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%. 

Double Polarization. The Clerget double polarization method is a procedure that attempts to account for the presence of interfering optically active compounds. Two polarizations are obtained a direct polarization, followed by acid hydrolysis and a second polarization. The rotation of substances other than sucrose remains constant, and the change in polarization is the result of inversion (hydrolysis) of the sucrose. 

The specific rotation ia water is [0 ] ° — +66.529° (26 g pure sucrose made to 100 cm with water). This property is the basis for measurement of sucrose concentration ia aqueous solution by polarimetry. 100°Z iadicates 100% sucrose on soHds. 

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... 

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... 

Polarimetry, in which a beam of polarized light is rotated by passage thru an optically active substance, has been applied to the quant detn of sucrose octanitrate (Vol 5, D1643-R Fef 61)... 

The following Tables constitute a list of most of the known, characterized derivatives of sucrose. The names of the solvents used for measuring the specific rotations are abbreviated as follows A, acetone C, chloroform Dm, dichloromethane E, ethanol M, methanol Mf, N,N-dimethylformamide P, pyridine and W, water. 

The reaction is pseudo-first order and rate is proportional to [Sucrose], The progress of the reaction can be studied by measuring the change in specific rotation of a plane of polarised light by sucrose. Let r0, r, and r are the rotation at initially (when t = 0), at any time t and final rotation, respectively. The initial concentration a is proportional to (r0 - r, ) and concentration at any time t, (a - x) is proportional to (r0 - rt). Thus, the rate constant may be obtained as... 

---