Optical rotation sugar molecule

The first such approach to the interpretation of optical rotation in terms of the conformational properties of carbohydrates was made by Whifien in 1956. He proposed that the observed rotation of an optically active molecule can be regarded as an algebraic summation of partial rotatory contributions of various conformational elements of asymmetry. For these contributions, empirical values were determined that allowed estimation of the net rotations of various cyclic sugars and cyclitols with fair accuracy. A more extensive treatment was presented by Brewster,and it was applied to a wide range of optically active, acyclic and cyclic compounds. The best correlations between the calculated and the experimental values were obtained with compounds that do not absorb in the near-ultraviolet and have predictable, fixed conformations, or for which the conformational populations can be reliably estimated. In the carbohydrate field, the calculations are quite simple for the poly-hydroxycyclohexanes, - and differences between the calculated and observed values for the rotation have been interpreted in terms of conformational equilibria. Similar comparisons have been made for the methyl D-aldopyranosides, although the lack of precision in the correlation does not allow a detailed treatment in terms of conformational populations. 

Optical rotation is an effect usually associated with complicated molecules such as sugars. In fact, even today the quality of sugar is determined by looking at its optical rotation. The sugar molecule has a helical... 

The structure of novobiocin (LVII) may be dissected into three fragments a substituted benzoic acid, a substituted coumarin, and a new sugar, noviose. Optical rotational data suggest that it is an a-glycosidei . The enolic group of the coumarin imparts acidic properties to the molecule. 

This can be analysed by optical rotation, with some rather interesting results. The sugars that were studied a few years ago were OL -methyl-maltoside, cellobiose and trehalose. They have one factor in common, they are composed of two glucose units, but with different linkages, maltose a-1-4, cellobiose B- 1-4, and trehalose 01-1-1. There are thus different conformations of this molecule, which consists of the same two sugar units. 

An understanding of the three-dimensional structures of molecules has played an important part in the development of organic chemistry. The first experiments of importance to this area were reported in 1815 by the French physicist J. B. Biot, who discovered that certain organic compounds, such as turpentine, sugar, camphor, and tartaric acid, were optically active that is, solutions of these compounds rotated the plane of polarisation of plane-polarized light. Of course, the chemists of this period had no idea of what caused a compound to be optically active because atomic theory was just being developed and the concepts of valence and stereochemistry would not be discovered until far in the future. 

Sucrose is an optically active molecule, [a]D = +66° but its optical activity is quite different from the sum of the optical activities of the two simple sugars, glucose and fructose. In fact an equimolar solution of glucose and fructose rotates light in... 

Biot made the remarkable observation that, when a beam of planr-polarized light passes through a solution of certain organic molecules such as sugar or camphor, the plane of polarization is rotated. Not all organic substances exhibit this property, but those that do are said to be optically active. 

Optical activity involving the ability to rotate the plane of polarized light was first observed by Biot in 1815-1835 in a number of naturally occurring organic compounds, such as turpentine, camphor, sugars, and tartaric acid. Since optically active compounds exhibited this property both in their crystalline form as well as in solutions, it was reasoned that this property is inherent in the molecules. Mitscher-lich in 1844 observed that although tartaric and racemic acids are isomeric, the former and its salt are optically active, while racemic acid is inactive. ... 

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