Fructose yield

Another name for glucitol obtained by reduction of d glucose is sorbitol it is used as a sweetener especially in special diets required to be low in sugar Reduction of D fructose yields a mixture of glucitol and mannitol corresponding to the two possi ble configurations at the newly generated chirality center at C 2... 

In a similar manner, ketones can react with alcohols to form hemiketals. The analogous intramolecular reaction of a ketose sugar such as fructose yields a cyclic hemiketal (Figure 7.6). The five-membered ring thus formed is reminiscent of furan and is referred to as a furanose. The cyclic pyranose and fura-nose forms are the preferred structures for monosaccharides in aqueous solution. At equilibrium, the linear aldehyde or ketone structure is only a minor component of the mixture (generally much less than 1%). 

Simple sugars undergo reaction with phenylhydrazine, PhNHNH2, to yield crystalline derivatives called osazones. The reaction is a bit complex, however, as shown by the fact that glucose and fructose yield the same osazone. 

Fig. 3. Product spectra of the wild-type (WT) GTFR and mutant S628D enzymes (200 U/L) incubated (7 days at 30 °C) with sucrose (146 mM) and different acceptor substrates (292 mM, Glc glucose Fru fructose). Yields are given in percentage (mol/mol Glc). Yields of higher oligosaccharides (DP >5) and...

The reaction with ethyl acetoacetate has been extended to glycolaldehyde, and to carbohydrates other than n-glucose, by employing different experimental conditions it is probably applicable to aldoses in general. With d-fructose, yields are lower, but two molar proportions of water are liberated and a crystalline product results. This has a constitution similar to that of II but with the D-omhfno-tetrahydroxybutyl chain at the /3-position on the furan ring. The reaction has been applied successfully to other ketoses and... 

Two methods are employed industrially to produce crystalline fructose, aqueous crystallization and alcoholic crystallization. Yields of fructose crystallized from water syrups are only of the order of 50%, due to the very high water solubility of the sugar, while the high viscosity of the concentrated solution results in long crystallization times, typically 50 hours or more (2). The second process requires the addition of lower alcohols (eg. ethanol) to a concentrated fructose syrup, generally 90% total solids or more, at temperatures of 50 C to 80""c and then cooling to cause crystallization. Fructose yields are from 70 to 80% and the total time involved is 8 to 12 hours (3). However, large quantities of... 

Conditions are slightly different during the so-called mannitol fermentation of sugars, especially of D-fructose. The process, which has been known for a long time, has recently been investigated more thoroughly by Bolcato. He found that 3 moles of D-fructose yield 2 moles of carbon dioxide, 2 moles of acetic acid and 2 moles of D-mannitol. Up to now, a maximum of 60% of the theoretically possible amount of D-mannitol has been isolated. The mechanism of the reaction may be assumed to be as follows ... 

Van Handel, E. (1957) Determination of fructose and fructose yielding carbohydrates with cold anthrone. Analytical Biochemistry 1 9(1), 1 93-1 94. 

Treat with lime water. Glucose, unlike fructose, yields no precipitate. 

In addition to enzymatic hydrolysis (see Section 5.8.1), inulin can be hydrolyzed chemically and subsequently dehydrated to yield hydroxymethylfurfural (van Dam et al., 1986), a key industrial chemical (Gretz et al., 1993 Fuchs, 1987 Kunz, 1993 Makkee et al., 1985 van Dam et al., 1986). Likewise, catalytic hydrogenation of D-fructose yields D-mannitol and D-sorbitol mixtures from which mannitol can be removed via crystallization (Fuchs, 1987). 

Upon reduction, hexose sugars like D-glucose, D-mannose and D-fructose yield commercially very attractive hexitols such as D-glucitol (sorbitol) or D-mannitol... 

The powdered-cellulose, flowing chromatogram of an unfermentable residue from the mixture obtained by the action of heat on n-fructose yielded a sirup containing a ketose having a mobility greater than that of D-fructose it may be n-psicose. D-Psicose (identified as the phenylosazone... 

Also by an oxidation resulting in splitting the chain at the ketone group fructose yields hydroxy acetic acid, CH2OH—COOH and tri-hydroxy butyric acid, HOOC—CH(OH)—CH(OH)—CHoOH. 

The Bilik reaction applied to 2-ketoses yield 2-hydroxymethyl aldoses in which the tertiary carbon originates from C2 of the ketose and the C2 hydroxyl is on the opposite side to the C3 hydroxyl of the ketose (in the Fischer projection). Thus, o-fructose yield o-hamamelose. The position of equilibrium, however, lies towards the straight-chain sugar, although it can be pulled over somewhat towards the branched-chain aldose by the addition of borate. The mechanism in Figure 6.9 again explains the main reaction, but not the formation of sorbose as a by-product, which probably arises from a metal ion-promoted hydride shift, as there is no isotope exchange with solvent. The Bilik reaction can be applied to the production of l-deoxy-o-xylulose from 2-C-methyl-D-erythrose the reaction is particularly clean and only the two... 

Structure of d-Fructose.—As d-fructose yields d-sor-bitol and d-mannitol on reduction, it must contain a straight chain of six carbon atoms. Acetic anhydride converts the carbohydrate into a penta-acetate, a fact which indicates that it contains five hydroxyl groups. On oxidation d-fructose does... 

Simple sugars can be reduced to polyhydric alcohols for example, glucose yields sorbitol, galactose yields dulcitol, and both mannose and fructose yield mannitol. Mannitol occurs in grass silage and is formed by the action of certain anaerobic bacteria on the fructose present in the grass. ... 

By means of the Fischer convention, the tetrahedral models for glucose, mannose, and arabinose are equivalent to the planar formulas given below. The formula for fructose is derived from the fact that fructose yields the same osazone as glucose when treated wdth phenylhydrazine (see above) it and glucose must have identical configurations for carbon atoms 3, 4, and 5. 

The reduction of ketoses yields both C-2 komers. For example, the reduction of D-g/ycero-tetrulose creates erythritol and d-threitol. Reduction of D-fructose yields D-glucitol and D-mannitol. 

Splitting of the hydroxyl group at C-1 of fructose yields a key intermediate l-deoxy-D-erythro-hexo-2,3-dm ose (Figure 4.34). In addition to the straight chain form, the corresponding furanoses and pyranoses also form in solution (Figure 4.35). Isomerisation of l-deoxy-D-eryt/jro-hexo-2,3-diulose along... 

The selective cleavage of carbon-carbon bonds in sugars can be achieved under relatively mild hydrogenolytic conditions using a ruthenium complex catalyst thus, besides D-mannitol and D-glucitol, D-fructose yielded up to 30% of glycerol. ... 

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