Glucose heating with

Glucose, heated with a dilute alkaline solution of picric acid, communicates to it a biood-red color. 

Analytical Characters.—(1.) Its intensely bitter taste. (3.) Its alcoholic solution, when shaken with a potassium salt, gives a yellow, crystalline ppt. (3.) An ammoniacal solution of cupric sulfate gives a green, crystalline ppt. (4.) Glucose, heated with a dilute alkaline solution of picric acid, communicates to it a blood-red color. (5.) Warmed with an alkaline solution of potassium cyanid, an intense red color is produced (the same effect is produced by ammonium sulfhydrate). (6.) Unbleached wool, immersed in boiling solution of picric acid, is dyed yellow. 

For this purpose a fermenter made of stainless steel having a 50 liter capacity is charged with 30 liters of a nutrient solution of 0.1% yeast extract, 0.5% cornsteep and 0.2% glucose, heated for one-half hour at 120°C for sterilization purposes, and after cooling, inoculated with a bacterial suspension of Bacillus lentus MS 2B4. 

This reaction can be reversed either by using the enzyme maltase as a catalyst or by heating with acid. Two molecules of glucose are farmed when this happens. 

Partially methylated derivatives of D-glucosone have been prepared by decomposition of the corresponding partially methylated phenylosazones with p-nitrobenzaldehyde osones have been obtained from 5-0-methyl-D-glucose phenylosazone and from 3,4,5-tri-O-methyl-D-glucose phenylosazone in this way.22 Although 6-0-methyl-D-glucose phenylosazone is not altered by heating with benzaldehyde or piperonal in aqueous ethanolic... 

Direct esterification of D-glucose by heating with 50% acetic acid at 100° was reported to yield 26-30% of the 6-acetate after chromatography on cellulose, together with unchanged starting-material and... 

Both D-[l- C]xylose and D-[5- C]arabinose were exposed to a concentrated phosphate buffer solution (pH 6.7). 1-Hydroxy-2-propanone (ace-tol) was distilled from the heated solution. Radioassay indicated that similar labeling [3- C] occurred in the acetol from both pentoses, with loss of the configurational difference thus, a 3-ketopentose or its enediol was suggested as an intermediate. Further work with 3-0- and 6-0-methyl-D-glucose and with 1-0-methyl-D-fructose indicated that /3-elimination from a 3-ketose or, in the case of a hexose, from a 3-ketose or a 4-ketose, or both, tautomerization of the resulting a-diketone to a /3-diketone, and hydrolytic cleavage are essential steps in the formation of acetol. 

In aqueous solution, both glucose (hemiacetal) and frnctose (hemiketal) exist as equilibrium mixtures of cyclic and open-chain carbonyl forms. Sucrose, however, is a single stable substance (acetal and ketal), and conversion back to glucose and frnctose requires more rigorous hydrolytic conditions, such as heating with aqueous acid. 

It has been shown also that the concentration of sucrose is a critical factor and that to obtain the highest yields very dilute solutions are necessary. Thus Fig. 1 shows the relative yields at different concentrations of sucrose heated with hydrobromic acid, all experiments being carried out under similar conditions. The highest yield of levulinic acid, weighed as crude material, was 79% of the theoretical and was obtained when the concentration of sucrose was 3%. Ploetz has also used the hydrobromic acid method to make levulinic acid and records a yield of 69% of the theoretical from crude sugar, 75% from glucose and 64 % from starch. 

Acids act similarly and rapidly to permanently disrupt the glyeosidic bonds. Thus polysaccharides degrade to their original monosaccharide units when heated with aqueous acids. Enzymes catalyze this degradation and provide both plants and animals with a source of glucose. 

Problem 22.53 A monosaccharide is treated with HCN, the product hydrolyzed and reduced to a carboxylic acid by heating with HI and P. What carboxylic acid is formed if the monosaceharide is (a) o-glucose, (6) D-mannose, (c) D-fructose, (d) o-arabinose, (c) o-erythrose ... 

Preparation of Copper(I) Oxide. Dissolve 2.5 g of copper vitriol (copper sulphate pentahydrate) in 15 ml of warm water and add 1.5 g of glucose. Heat the solution and rapidly add 2.5 ml of a 20% sodium hydroxide solution to it. Stir the mixture and let it stand for an hour. Wash the precipitate with distilled water. Write the equations of the reactions. 

Pentosans. These compounds are polysaccharides which may he considered as anhydrides of pentose sugars, after the manner of the hexosans. sucrose, starch, from glucose, fructose. When pentosans or pentoses are heated with hydrochloric ot sulfuric acid, furfural C fljO CHO is formed, and addition of aniline produces a red color. Pentosans are present in gummy carbohydrates, in bran of wheat seed, and in woods. 

Examine in a polarimeter and note dextrorotation. Then heat with a little dilute sulphuric acid, neutralise carefully, and again examine in polarimeter. Note laevorotation. Fructose is more lsevorotatory than glucose is dextrorotatory. 

Amygdalin (the glucoside of bitter almonds) is a white crystalline compound, soluble in water, readily hydrolysed on heating with dilute sulphuric acid to benzaldehyde, hydrocyanic acid and glucose. 

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