Carbohydrate decomposition

P8.04.09. BATCH AND CSTR OPERATION WITH AN MH4 RATE EQUATION A carbohydrate decomposition has the rate equation... 

As a consequence of bottle aging, carbohydrate conversions can occur, although slowly at cellar temperature, to form the caramel-like 2-furfural aroma for example, in aged Madeira wines. Rapp and Giintert (86MI141) have shown that such carbohydrate decomposition in Riesling wines leads to 2-furfural 9,2-acetylfuran 10, ethyl furan-2-carboxylate 11, 2-formyl pyrrole 12, and 5-hydroxymethylfurfural 13. 

Previously we have studied BSA and carbohydrate decomposition using TPD MS for individual organics in a condensed state, and those adsorbed to a... 

Around and above 100°C, the boiling of water is generally prevented by using sealed containers this allows the detection of other phenomena such as carbohydrate decomposition. This is observed in the calorimetric curves of reconstituted foods such as milk powders and in the curves of raw foods such as coffee beans, chicory roots, and cereal grains [98-101]. 

Self-healing can lead to self-ignition of the food if sufficient oxygen is available. The main phenomena involved in thermal runaway of food products are fermentation, carbohydrate decomposition, lipid oxidation, and probably polyphenol and protein oxidation. However, other weaker exothermic effects such as Maillard reactions could participate in the initial temperature increase. 

The melting points of carbohydrates (sugars) are not usually sharp and they are perhaps best expressed as decomposition points. 

Commercial lecithin is insoluble but infinitely dispersible in water. Treatment with water dissolves small amounts of its decomposition products and adsorbed or coacervated substances, eg, carbohydrates and salts, especially in the presence of ethanol. However, a small percentage of water dissolves or disperses in melted lecithin to form an imbibition. Lecithin forms imbibitions or absorbates with other solvents, eg, alcohols, glycols, esters, ketones, ethers, solutions of almost any organic and inorganic substance, and acetone. It is remarkable that the classic precipitant for phosphoHpids, eg, acetone, dissolves in melted lecithin readily to form a thin, uniform imbibition. Imbibition often is used to bring a reactant in intimate contact with lecithin in the preparation of lecithin derivatives. 

Cellobiose was prepared first by Skraup and Konig by the saponification of the octaacetate with alcoholic potassium hydroxide, and the method was improved by Pringsheim and Merkatz.3 Aqueous barium hydroxide also has been employed for the purpose, and methyl alcoholic ammonia has been used extensively for the hydrolysis of carbohydrate acetates. The method of catalytic hydrolysis with a small quantity of sodium methylate was introduced by Zemplen,i who considered the action to be due to the addition of the reagent to the ester-carbonyl groups of the sugar acetate and the decomposition of the addition compound by reaction with alcohol. The present procedure, reported by Zemplen, Gerecs, and Hadacsy, is a considerable improvement over the original method (see Note 2). 

It would be reasonable to expect that the decomposition of the N,N-dimethylimino ester chlorides proceeds via a bimolecular mechanism already demonstrated for the thermal decomposition of simple imino ester salts (79). In the carbohydrate series, where an isolated secondary hydroxyl group is involved, such a process would result in chlorodeoxy sugar derivatives with overall inversion of configuration, provided that the approach of the chloride ion is not sterically hindered. Further experiments are in progress in this laboratory utilizing additional model substance to establish the scope and stereochemical course of the chlorination reaction. 

Although the Tollens reaction is a useful test for reducing sugars, it doesn t give good yields of aldonic acid products because the alkaline conditions cause decomposition of the carbohydrate. For preparative purposes, a buffered solution of aqueous Br2 is a better oxidant. The reaction is specific for aldoses ketoses are not oxidized by aqueous Br2. 

Mond process The purification of nickel by the formation and decomposition of nickel carbonyl, monomer A small molecule from which a polymer is formed. Examples CH2=CH2 for polyethylene NH2(CH2)6NH2 for nylon, monoprotic acid A Bronsted acid with one acidic hydrogen atom. Example CH COOI I. monosaccharide An individual unit from which carbohydrates are considered to be composed. Example C6H(206, glucose, multiple bond A double or triple bond between two atoms. 

The melting points of carbohydrates (sugars) are not usually sharp and they are perhaps best expressed as decomposition points, t The small capital letter prefix refers to configuration, relat to D- lyceraldehyde, 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 dtxtro and loevo. Thus we have d-(—)-fructose and ,-(+).arabinose. 

Gums are complex carbohydrates exuded from plants, or produced by the decomposition of vegetable matter, that have been used since remote times as adhesives, sizes, and binders (see Table 73). Most gums are tasteless and odorless solids that either dissolve or swell in water to form adhesive, viscous mucilages. When the water evaporates from a mucilage, the... 

Conventionally, central and special metabolic pathways are distinguished. Central pathways are common to the decomposition and synthesis of major macromolecules. Actually, they are much alike in all representatives of the living world. Special cycles are characteristic of the synthesis and decomposition of individual monomers, macromolecules, cofactors, etc. Special cycles are extremely diversified, especially in the plant kingdom. For this reason, the plant metabolism is conventionally classified into primary and secondary metabolisms. The primary metabolism includes the classical processes of synthesis and deeradation of major macromolecules (proteins, carbohydrates, lipids, nucleic acids, etc.), while the secondary metabolism ensuing from the primary one includes the conversions of special biomolecules (for example, alkaloids, terpenes, etc.) that perform regulatory or other functions, or simply are metabolic end byproducts. 

Subsequently, in the course of the total synthesis, we established that glycosyla-tion of the macrolactam alcohol or various silyl ethers by a range of protocols is not feasible. Repeated initiatives along these fines resulted in complete decomposition of the carbohydrate systems and low recovery of the macrocyclic substrate (<15%). The principal reason for such unsatisfactory outcomes proved to be the notorious lack of solubility of the parent alcohol of 76 in a wide variety of solvents the 14-membered alcohol is sparingly soluble in methanol at ambient temperatures. Clearly, out initial efforts towards the use of catalytic RCM in constructing the macrolactam segment of Sch 38516 required additional investigation. 

Several other types of photochemical reactions involving unsaturated carbohydrates have been reported. One of these is38 photochemical, E -Z isomerization of the groups attached to a double bond (see Scheme 5). A second is the internal cycloaddition between two double bonds connected by a carbohydrate chain.39-41 Although the carbohydrate portion of the molecule is not directly involved in this cycloaddition, its presence induces optical activity in the cyclobutane derivatives produced photochemically. Finally, a group of acid-catalyzed addition-reactions has been observed for which the catalyst appears to arise from photochemical decomposition of a noncarbohydrate reactant.42-44... 

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