Degradation and dehydration

The aldehyde-fimctionalized resin was subjected to a series of washes of increasing methanol concentration agarose beads may be subject to solvent-stress-related degradation and dehydration if immediately placed in 100% (v/v) methanol without gradually displacing the water absorbed by the resin. 

Silica gel and aluminium oxide layers are highly active stationary phases with large surface areas which can, for example, — on heating — directly dehydrate, degrade and, in the presence of oxygen, oxidize substances in the layer This effect is brought about by acidic silanol groups [93] or is based on the adsorption forces (proton acceptor or donor effects, dipole interactions etc) The traces of iron in the adsorbent can also catalyze some reactions In the case of testosterone and other d -3-ketosteroids stable and quantifiable fluorescent products are formed on layers of basic aluminium oxide [176,195]... 

Phenolic networks are well known for their excellent thermal and thermo-oxidative stabilities. The mechanisms for high-temperature phenolic degradation include dehydration, thermal crosslinking, and oxidation, which eventually lead to char. 

From the base-catalyzed degradation of D-fructose (pH 8.0), Shaw and coworkers147 identified 18 compounds, none of which was (a) isomeric with the starting material, or (b) a simple dehydration product. Among the products, the hydroxy-2-butanones and 1-hydroxy-2-propanone (acetol) were shown to participate in forming the carbo-cyclic products identified, but the mechanism of their formation was not elucidated. Several furan derivatives were isolated, but no lactic acid was isolated. In a similar study but with weak acid,41 most of the products were formed by a combination of enolization and dehydration steps, with little fragmentation. 

Alcohol from dehydration contains a certain quantity of nitrocellulose, i.e. its soluble fractions, mostly degraded, and a certain amount in suspension. Experiments have shown that about 2.2 g of dissolved nitrocellulose and 1.3 g of nitrocellulose in suspension—a total 3.5 g—occur in 11. of 70% alcohol from centrifuges. Sometimes however, the content of nitrocellulose in the alcohol may reach 10-12 g/1. 

Freshly cut oranges or their juices may be exposed in an open glass for several hours without appreciable loss of I he vitamin because of the protective effect of the acids present and the practical absence of enzymes that catalyze its destruction. In potatoes, when baked or boiled, there is a slight loss of the vitamin, blit if they are whipped lip with air while hot, as in the production of mashed potatoes, a large fraction of the initial vitamin content usually will be lost. In freezing foods, it is common practice to dip them in boiling water or to treat them briefly with steam to inactivate enzymes, after which they arc frozen and stored at very low temperatures. In this state, the vitamin is reasonably stable. Vuamin C degradation in dehydrated food systems is described shortly. 

At elevated temperature a joint action of thermo-chemical concrete degradation, V, accounting for high temperature related micro-cracking and dehydration, and external load-related cracking, d, is described by the total damage parameter, D, given by [7],... 

The typical caramel flavor is the result of a number of sugar fragmentation and dehydration products, including diacetyl, acetic acid, formic acid, and two degradation products reported to have typical caramel flavor by Jurch and Tatum (1970), namely, acetylfor-moin (4-hydroxy-2,3,5-hexane-trione) and 4-hydroxy-2,5-dimethyl-3(2H)-furanone. 

Aldehydes result from the decomposition of certain ozonides. The technique is similar to that used for the preparation of ketones (method 182). High yields are obtained by catalytic hydrogenation of the ozonides. This step coupled with Grignard and dehydration reactions has been used as a procedure for the degradation of an aldehyde to its next lower homolog, viz.,... 

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