Fructose optical rotation

The small capital letter prefix refers to configuration, related to n glyceraldehyde, and not to the direction of optical rotation. The sign of optical rotation is expressed as (+) and (—) or as d and I or by the words dextro and Uuvo. Th is we have n.( —)-fructose and ,-(+).arabinose. 

Sucrose, in contrast, is a disaccharide of almost universal appeal and tolerance. Produced by many higher plants and commonly known as table sugar, it is one of the products of photosynthesis and is composed of fructose and glucose. Sucrose has a specific optical rotation, of +66.5°, but an... 

The calcium carbonate precipitate was removed by filtration, and the filtered solution was found to contain 1,436 g of fructose as determined by optical rotation. A small amount of calcium bicarbonate was present as an impurity in solution and was removed by the addition of oxalic acid solution until a test for both calcium and oxalic acid was negative. The insoluble calcium oxalate precipitate was removed by filtration. 

Optical Rotations and Melting Points of Glycosyl Di-D-fructose Dianhydrides and Their Per-0-acetyl Derivatives... 

Diheterolevulosans, 209-211, 240 Dihexulose dianhydrides, 207 -266, see also Caramels Di-D-fructose dianhydrides 13C NMR spectra, 245-246 conformation, electronic control, 224-228 conformational rigidity, energetic outcomes, 228 hexulopyranose rings, 226 historical overview, 210-213 H NMR spectra, 248 -249 intramolecular hydrogen-bonds, 227 isomerization, 231 -232 1,2-linked, ero-anomeric effect, 224-225 listing, 240-241 nomenclature, 208-210 optical rotations and melting points, 242-243 protonic activation... 

Per-O-acetyl dihexulose dianhydrides l3C NMR spectra, 247 H NMR spectra, 250-251 optical rotations and melting points, 244 Per-O-acetyl fructose glucose, H-NMR spectra, 252... 

A large number of polyfructosans that have been reported from time to time by different authors have been investigated by Schlubach and his associates. In order to obtain polysaccharides of constant optical rotation, 100 to 300 precipitations from aqueous solution by the addition of alcohol were necessary. Fifty to 150 precipitations from chloroform solution with petroleum ether were required for purification of the acetate derivatives. These were methylated according to the procedure of Haworth and Straight,24 and upon hydrolysis partially methylated fructoses were obtained. 

Thus, if optically active substance is involved in the reaction, the change in optical rotation can be used directly to follow the progress of reaction. The inversion of sucrose in presence of HC1 giving rise to fructose and glucose can, thus, be monitored polarimetrically. 

These are some examples of the use of i.r. spectra in the analysis and identification of carbohydrates in foods and natural products. Very often, these spectroscopic techniques are complementary to others, such as the study of aldobiouronic acids obtained by hydrolysis of peach-gum polysaccharides by their optical rotations and their i.r. spectra.100 However, the i.r. results appear to be sufficiently reliable to be used in the detection of traces of fructose and glucose, and to determine the d.e. (dextrose equivalent) of corn syrups, as well as the quantitative carbohydrate content in different products.101... 

Methylation of verbascose, and hydrolysis, gave21 2,3,4,6-tetra-O-methyl-D-galactose (identified as the crystalline anilide), 2,3,4-tri-O-methyl-D-galactose (crystalline, identified by converting it into the 6-0-trityl derivative), 1,3,4,6-tetra-O-methyl-D-fructose (identified by analytical data and by its optical rotation), and a tri-O-methyl-D-glucose which, on further methylation, was converted into 2,3,4,6-tetra-O-methyl-D-glucose (identified through the crystalline anilide). 

Chemists have known about racemates since Pasteur, at 26 years of age, told the Paris Academy of Sciences how he used tweezers to separate two types of crystals of salts of tartaric acid, which rotate polarized light clockwise (d, dextro) or counterclockwise (l, levo). Unfortunately, this correspondence does not always hold true. In fact, the magnitude and even the direction of optical rotation are complicated functions of the electronic structure surrounding the chiral center. For example, the common enantiomer of the sugar fructose is termed d because of the stereochemical orientation about the chiral atom. But this enantiomer actually rotates the plane of polarization to the left, and its mirror image, L-fructose, rotates the plane of polarization to the right. 

An enzyme known as invertase catalyzes the hydrolysis of sucrose to an equimolar mixture of D-glucose and D-fructose. During the hydrolysis, the optical rotation of the solution changes from (+) to (-). What can you conclude from this observation ... 

Assay Adjust the flow of the Glucose Substrate to such a rate that a fractional conversion of 0.2 to 0.3 will be produced, based on the estimated activity of the sample. Calculate the fractional conversion from optical rotation values obtained on the starting Glucose Substrate and the sample effluent, as specified under Calculations, below. After establishing the correct flow rate, run the column overnight (16 h minimum), then check the pH of the Glucose Substrate, and readjust if necessary to the specified pH. Measure the flow rate, and collect a sample of the column effluent. Cover the effluent sample, allow it to stand for 30 min at room temperature, and then determine the fractional conversion of glucose to fructose (see Calculations, below). If the conversion is less than 0.2... 

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