Alcohols carbohydrates

Pulsed amperometric detection (PAD), introduced by Johnson and LaCourse (64, 65) has greatly enhanced the scope of liquid chromatography/electrochemistry (66). This detection mode overcomes the problem of loss of activity of noble metal electrodes associated with the fixed-potential detection of compounds such as carbohydrates, alcohols, amino acids, or aldehydes. Pulsed amperometric detection couples tlie process of anodic detection with anodic cleaning and cathodic reactivation of a noble metal electrode, thus assuring a continuously cleaned and active... 

Various individual amino acids Various carbohydrates Alcohols and polyols Surfactants... 

Carbohydrate ketones.J This reagent is recommended for oxidation of carbohydrate alcohols to ketones without epimerization of axial a-substituents to the more stable cpimcrs. Ru04 has been used successfully, but is expensive when used in stoichiometric amounts as required for consistent results. 

The fact that a carbohydrate can be vinylated in the presence of a base catalyst in,an aqueous system is a good argument for the existence of carbohydrate alcoholates in aqueous media. However, successful vinylation does not imply that the concentration of the alcoholate is necessarily high. Because the interaction between the carbohydrate and the hydroxide ion is rapidly reversible, the concentration of the alcoholate may not have to be large for vinylation to proceed at a moderate rate. 

At this stage of our knowledge, the occurrence of hydrogen bonding between hydroxyl groups and anionic oxygen in carbohydrate alcoholates has not been shown conclusively. That it probably does occur is strongly... 

Every analysis performed on columns of this type (for example, carbohydrates, alcohols, organic acids, mixtures of these) can be improved with a column in the most suitable ionic form, even though solutions with compounds of differing types may impose the choice of a compromise. In analytical practice, however, it is not advisable to make an in-column conversion from one form to another, for the resin could shrink or even swell in relation to the type of cation linked. The effect of fixed-cation is made obvious when the compounds under analysis can coordinate with it, as in the case of carbohydrates. For example, the linkage of sugars with three adjacent hydroxyls may be more stable than those that have only two, with obvious effects in the resolution of the analytes. Finally, it is advisable to use a guard column to prolong the life of the... 

Average percentage of positive responses to 4 types of catabolic and physiological tests. Exoenzymes presence was tested on 7 macromolecules (Arcachon) and on 2 macromolecules (Roscoff). The organic compounds utilization index was calculated on the basis of 34 substrates in Arcachon (amino acids, carbohydrates, alcohols, fatty and organic acids) and on 13 substrates in Roscoff (principally carbohydrates and alcohols). IP initial bacterial population. P microcalorimetric peak. FSS final steady-state. 

During the increase of the heat production rate, the succession of populations was very rapid, the strains isolated at different incubation times never clustered at a similarly high level. The values of index of utilization of small molecules (amino acids, carbohydrates, alcohols) showed a net tendency to decrease and reach a minimum indicating physiological specialization, paralleled by the maximum value of the specific heat dissipation rate q. ... 

Fig. 6 Evolution of microbial catabolic potentialities during a "summer" type microcalorimetric response to eutrophication. The five bar charts characterize the specialization of the bacterial population, expressed as the ability to metabolize a variety of organic substrates (carbohydrates, alcohols, amino acids etc.).

Actually, the adducts are cleaved by various primary or secondary alcohols, including various carbohydrate alcohols, and thus can be used to obtain amino-polysaccharides. 

High stereoselectivity is observed in the a-glucosylation of carbohydrate alcohols with 3,4,6-tri-O-benzyl-D-glucal and phenylselenenyl chloride30. 

The sugar alcohols or carbohydrate alcohols may be classified as a group of compounds obtained as reduction products of ketoses or aldoses or homologous compounds. Further, they may be considered as compounds of carbon, hydrogen and oxygen, containing typically one hydroxyl group for each carbon atom present in the molecule. Such a... 

Refractive index monitors are used in food analysis, for detecting carbohydrates, alcohols, and other substances with weak or no UV absorption. 

Typical 13C-spectra for humic acids from a range of sources are shown in Figures 2 and 3. Five major regions of resonance can be recognised. These are 0-50 ppm (alkyl carbon), 50-108 ppm (carbohydrate, alcohol, ether and the COOH t-carbon of amino acid), 108-160 ppm (aromatic carbon), 160-200 ppm (carboxylic, ester, amide carbon) and 200-220 ppm (ketonic or aldehydic carbon). 

Good selectivity among secondary carbohydrate alcohols has been achieved, but the regiochemistry is structure-dependent. a-Methylglucoside can be selectively acylated at the 2,6-positions in 89% yield and a-methyl 4,6-0-ben-zylidineglucoside can be selectively acylated at the 2-position in 77% yield."... 

More than monohydric alcohols can be only incompletely dehydrogenated, and carbohydrate alcohols do not survive attempted dehydrogenation. 

Das et al. [8] described an operationally simple procedure for microwave-activated acetylation of carbohydrate alcohols by acetic anhydride, which uses only 0.1 equiv. of the powerful indium chloride catalyst. Peracetates were produced in good to excellent yields. Comparison of this method with others which use well established catalysts (pyridine, I2, Cu(OTf)2, C0CI2), either with an appropriate solvent or neat (following standard conditions), shows that under microwave irradiation conditions indium chloride is the best choice providing higher yields than those without microwave energy. 

Vonach, R., Lendl, B., and Kellner, R. High-performance liquid chromatography with real-time Fourier-transfonn infrared detection for the determination of carbohydrates, alcohols and organic acids in wines. J. Chwmatogr. A, 824, 159-167, 1998. 

Tf20 has been used as a promoter in glycosylations of carbohydrate alcohols by glycosyl fluorides. 

Pyrldlnlura dlchromate-acetlc anhydride Is very simple and efficient for use In the oxidation of carbohydrate alcohols. Examples Illustrating the oxidation of secondary alcohols In pyranold and furanold compounds In almost quantitative yield were provided, ... 

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