Structure of sucrose

Hudson10 showed that the mutarotation of fructose in water at 30° is eleven times faster than that of glucose. He therefore assumed that in a sucrose solution which is undergoing very rapid inversion with invertase at that temperature, practically all of the fructose has reached equilibrium and exists as a mixture of its a and 0 forms, while the glucose is being liberated in only one form which, however, slowly passes to its a, 0 equilibrium mixture. The drop in rotation between the apparent and real curves of inversion by invertase must therefore be due almost entirely to the mutarotation of glucose. Hudson thus showed that the D-glucose liberated from sucrose by invertase had a specific rotation between [ ]d +100° and +125° and is thus most likely the a-form. 

Data obtained by other workers through different experimental approaches also point to the same conclusion. Weidenhagen11 demonstrated that at its optimum pH 7, maltase (a-glucosidase), which had 

There is also strong evidence for the type of glycosidic linkage existing in the fructose constituent of the sucrose molecule. Schlubach and Rauchalles18 showed that invertase hydrolyzes sucrose and methyl /3-D-fructofuranoside at approximately the same rate, indicating that 

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Figure 13.17.1 The molecular structure of sucrose, a disaccharide of glucose and fructose. Asterisks indicate the hydroxyl groups replaced with chlorine atoms in the synthetic sweetner.

Figure 9.18 Structure of sucrose. Sucrose is a disaccharide which has only one possible structural form, there being no free anomeric hydroxyl group. 

Acetal and ketal linkages are widely foimd in nat-inal sugars and polysaccharides. The structure of sucrose is a splendid example. Sucrose is a disaccharide, composed of two linked monosaccharide imits, glncose in pyranose ring form and frnctose in fmanose ring form. As we have seen above,... 

Problem 22.39 (u) Give the structure of sucrose (cane and beet sugar) from the following information (1) It is hydrolyzed by maltase or emulsin to a mixture of d-( )-glucose and D-(-)-fructose. (2) It does not reduce Fehling s solution and does not mutarotate. (3) Methylation and hydrolysis gives 2,3,4.6-tetra-O-methyl-D-glucose and a tetramethyl-D-fructose. (b) What structural features are uncertain ... 

Fig. 1. Structural representations of sucrose (a) Haworth perspective formula, and (b) conformational structure of sucrose in solid crystals. Adapted from...

A final example is the work of Wolfram and Shafizadeh1 8 on the structure of sucrose, for which Hudson had given an a-D configuration for the o-glucopyranosyl moiety, based on the results of invertase-catalyzed hydrolysis. These workers,128 using data from the methyl n-fructofuranosides, demonstrated that this hydrolysis is not accompanied by a Walden inversion and that the original work of Hudson was correct. 

Considering these problems, we tested a computer extrapolation (6) for sucrose, shown in the conformation maps in Figure 4. Four sets of crystal parameters were used, those from the structure of sucrose (S) (45) and those from the sucrose component of raffinose pentahydrate... 

Because sucrose is hydrolyzed by enzymes that specifically assist hydrolysis of both a glycosides (such as yeast a-glucosidase) and /3-fructosides (such as invertase), it is inferred that the glucose residue is present as an a glucoside and the fructose residue as a /3 fructoside. If so, the remaining uncertainty in the structure of sucrose is the size of the rings in the glucose and fructose residues. 

Figure 20-5 Summary of reactions used to establish the ring structure of sucrose...

Examine the structures of sucrose, the natural sweetener, and saccharin, sodium cyclamate and aspartame (Nutrasweet), three of the most common artificial sweeteners. What, if any, structural features do these molecules have in common Compare electrostatic potential maps for the different sweeteners. Are there any significant features in common Based on your findings, do you think it is likely that entirely different artifical sweeteners might be discovered Explain. 

Very successful experiments were carried out on the oxidation of sucrose, one mole of which needs three moles of periodic acid, with the formation of one mole each of formic acid and a tetraaldehyde. The latter is oxidized by bromine to a tetracarboxylic acid subsequent acid hydrolysis of the oxygen bridges affords a mixture of acids, all of which were isolated and identified. These results brought in 1943 a confirmation of the structure of sucrose which was discussed, and which gained the approval of C. S. Hudson who, before that, was a little doubtful about the furanoid form of the D-fructosyl group. Similar work was done later with trehalose. In the same way, J. . Courtois obtained confirmation of the structure of raffinose, and established that of stachyose. 

The crystal structure of sucrose has been established by X-ray diffraction and neutron diffraction studies. The packing of sucrose molecules in the crystal lattice is determined mainly by hydrogen bond formation between hydroxyl groups of the fructose moiety. As an example of the type of packing of molecules in a sucrose crystal, a projection of the crystal structure along the a axis is shown in Figure 4-15. The dotted square represents one unit cell. The crystal faces indicated in this figure follow planes between adjacent sucrose molecules in such a way that the... 

Fig. 8.1. The four-center hydrogen bond in the crystal structure of sucrose by neutron diffraction (SUCROS04)...

Problem 35.11 When (+)-sucrose is hydrolyzed enzymatically, the D-glucose initially obtained mutarotates downward to 4- 52.7°. What does this fact indicate about the structure of (+)-sucrose ... 

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