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Studying the Composition of Sugars in Solution

If only one, or none, of the forms is known in the crystalline state, polarimetry does not yield any useful results. It was not even certain, for example, before the advent of n.m.r. spectroscopy, whether the one known crystalline form of D-ribose is the a- or the / -pyranose its muta-rotational change is small, but complex.5 [Pg.18]

Nuclear magnetic resonance spectroscopy can detect the presence of aldehydo and keto forms of sugars in those rare instances where they occur to the extent of 1% or more in equilibrium, their proportion has thus been determined.16,20,23 24 However, the percentage of the acyclic forms present in equilibrium is usually very small, and is much below the limit of detection by n.m.r. spectroscopy other methods have, therefore, to be used. [Pg.20]

After studying several methods, Swenson and R. Barker concluded that infrared (i.r.) spectroscopy is the most suitable method for this purpose.25 They thus determined the proportion of the carbonyl form in glyceraldehyde and in several phosphorylated sugars. However, the limit of detection of i.r. is about the same as that of n.m.r. spectroscopy they could not detect the keto form in a solution of D-fructose. [Pg.20]

The hydrated aldehydo or keto form can only be detected by n.m.r. [Pg.21]

The composition of aqueous solutions of D-arahino-2-hexulose (d-fructose) has also been studied by laser-Raman spectroscopy.45 (The composition of solutions of D-fructose appears to have been determined by more methods, and more often, than that of any other sugar.20) [Pg.23]

On the other hand, the use of specifically l3C-labelled sugars, developed by Barker and Serianni,5-13 has been applied to many sugars it is particularly useful when the label is in position 1. Labelling results in an 100-fold increase of the l3C signal of the labelled carbon atom, making it possible to detect components occurring in very small proportions, down to 0.01% for example, for ribose10 at 25°, —0.05% of free aldehyde. These results are discussed in Sections III,4 and III,5. [Pg.21]

The composition of many aldoses and two ketoses has been determined14 by, 3C-n.m.r. spectroscopy the results agreed well with those from previous determinations made from H-n.m.r. spectra. [Pg.21]

Working at low temperatures (0-4°), h.p.l.c. on a cation-exchange resin in the calcium form will separate the pyranose anomers of most of the aldo-hexoses and -pentoses18 under these conditions, mutarotation is slower than separation. The furanoses are not separated, because they interconvert too rapidly, but, at—2 5 to—45 °, the two furanose forms of D-galac-tose and L-fucose have been separated.19 Attempts to separate the various forms of sugars on a preparative scale [p. 24] have not succeeded so far.20 [Pg.22]


The majority of the many methods used to study the composition of equilibrium solutions of carbohydrates examine the mixture without separating the individual components. With the discovery that the anomeric forms of sugars could be readily separated by gas chromatography of their tri-methylsilyl ethers, a new approach to the problem was found. A protocol was developed for the direct gas chromatographic analysis of the amount of each anomer present in an aqueous solution. The protocol can be used on the micro scale and can be used in enzyme assays such as that for mutarotase. The method has been made more effective by combining gas chromatography with mass spectrometry. It is shown how mass spectral intensity ratios can be used to discriminate anomers one from another. The application of these methods to the study of complex mutarotations is discussed. [Pg.9]

Tnformation about the characteristics of keto-hexoses in solution has been - derived mainly from optical rotatory data (I, 2, 3, 4) and in recent years by application of the principles of conformational analysis (5, 6). In the current study an attempt is made to describe the conformation and composition of these sugars in solution by nuclear magnetic resonance (NMR) spectroscopy, a highly sensitive means for examining stereochemistry and for differentiating between isomeric species. [Pg.47]

The relationship of the solvent composition to RF values of the sugars was mentioned in a previous Section. The solvents used are of two types those partially miscible with water, e.g., phenol and those completely miscible with water, e.g., ethanol. Three factors need to be considered in the selection of a solvent mixture its suitability for the particular separation desired, its stability as a mixture, and its reactivity toward the solute being separated. Jeanes and coworkers23 and Jermyn and Isherwood26 have studied the suitability of a large number of solvent mixtures. [Pg.315]

Phase equilibria in water have been described by Kelly, who studied the effect of hexoses, sucrose, and inorganic salts on each other. The conclusion was reached that, for sucrose, the solubility of the second solute influences the composition at the invariant point, but for D-fructose, this effect is zero because of the high solubility of this sugar in water. Viscosity and density have also been evaluated at different temperatmes in methyl sulfoxide, and were fitted to appropriate equations by use of least-squares methods. The apparent molal volume calculated in this way is in perfect agreement with the theoretical data, whereas the differences for D-glucose and sucrose are 8 and 4%, respectively. [Pg.236]

The mutarotations of the sugars listed in Table III and those for many other sugars follow the first-order equation. The activation energy averages about 17,000 cal./mole this value corresponds to an increase in rate of 2.5 times for a 10° rise in temperature. The conformity of the mutarotation data to the first-order equation makes it probable that the main constituents of the equilibrium solution are the a- and jS-pyranose modifications. The actual composition may be calculated from the optical rotations of the equilibrium solution when the rotations of the pure a- and /3-isomers are known. Data of this type are included in Table III. Independent confirmation of the composition of the equilibrium solutions is provided by studies of the rates of bromine oxidation of the sugars, the results of which are also found in Table III. [Pg.51]

The equilibrium solutions are oxidized at rates intermediate between those for the individual anomers (see Fig. 2 and 3), and the oxidation curve is composed of a rapid phase followed by a slow phase. Extrapolation of the slow portion (on a semilogarithmic plot) to zero time gives the amount of the two anomers in the equilibrium solution. The composition of equilibrium solutions of several sugars as determined in this manner agrees with that obtained by optical rotation studies (see Table III, Chapter I). [Pg.341]


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Composition of solutions

Composition of sugars

Composition sugar

Solution composition

Solution studies

Studying composite

Studying in composites

Sugars in solution

The Sugars

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