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Reactions degradative

Carbohydrates undergo a number of isomerization and degradation reactions under both laboratory and physiological conditions For example a mixture of glucose fructose and mannose results when any one of them is treated with aqueous base This reaction can be understood by examining the consequences of enohzation of glucose... [Pg.1056]

Because high temperatures are required to decompose diaLkyl peroxides at useful rates, P-scission of the resulting alkoxy radicals is more rapid and more extensive than for most other peroxide types. When methyl radicals are produced from alkoxy radicals, the diaLkyl peroxide precursors are very good initiators for cross-linking, grafting, and degradation reactions. When higher alkyl radicals such as ethyl radicals are produced, the diaLkyl peroxides are useful in vinyl monomer polymerizations. [Pg.226]

Thermal, Thermooxidative, and Photooxidative Degradation. Polymers of a-olefins have at least one tertiary C-H bond in each monomer unit of polymer chains. As a result, these polymers are susceptible to both thermal and thermooxidative degradation. Reactivity in degradation reactions is especially significant in the case of polyolefins with branched alkyl side groups. For example, thermal decomposition of... [Pg.426]

Bisphosphites such as (7) combine excellent reactivity, straight-chain selectivity, and high resistance to the typical phosphite degradation reactions (29). Further, the corresponding 0x0 catalysts are excellent olefin isomerization catalysts so that high normal-to-branched isomer ratios are obtained even from internal olefins, enabling, in certain instances, the use of inexpensive mixed isomer olefin feedstocks. [Pg.471]

J. Liska and E. Borsig, Chem. Listy 86(12), 900 (1992). A review of substitution reactions as well as degradation reactions. [Pg.335]

Similar degradation reactions were used to estabUsh the absolute configuration of mocimycin (kirromycin) (1, R = H) (46), the constitution of which had been described previously (7,47). The chemical stmctures of most other subsequentiy discovered elfamycins have been deterrnined spectroscopically and assignments of absolute configurations are not complete. The elfamycin stmctures shown in Figure 1 have complete stereochemical details that have been in part ascertained experimentally and in part are assumed to correspond to the aurodox topography. [Pg.524]

Radiation-induced degradation reactions are in direct opposition to cross-linking or curing processes, in that the average molecular weight of the preformed polymer decreases because of chain scission and without any subsequent... [Pg.424]

At temperatures near the critical temperature, many organic degradation reactions are rapid. Halogenated hydrocarbons loose the halogen in minutes at 375°C (38). At temperatures typical of nuclear steam generators (271°C (520°F)), the decomposition of amines to alcohols and acids is well known (39). The pressure limits for the treatment of boiler waters using organic polymers reflect the rate of decomposition. [Pg.369]

This reaction is favored by higher reaction temperatures and polar solvents. Another degradation reaction common to ethers is oxidation, especially when the a-carbon is branched (17). Polymeric ethers of all types must not be exposed to oxygen, especially in the presence of transition metals because formation of peroxides can become significant. [Pg.515]

Nonicosahedral carboranes can be prepared from the icosahedral species by similar degradation procedures or by reactions between boranes such as B H q and B H with acetylenes. The degradative reactions for intermediate C2B H 2 species (n = 6-9) have been described in detail (119). The small closo-Qr Yi 2 species (n = 3-5 are obtained by the direct thermal reaction (500—600°C) of B H using acetylene in a continuous-flow system. The combined yields approach 70% and the product distribution is around 5 5 1 of 2,4-C2B3H2 [20693-69-0] to l,6-C2B Hg [20693-67-8] to 1,5-C2B3H3 [20693-66-7] (120). A similar reaction (eq. 60) employing base catalysts, such as 2 6-dimethylpyridine at ambient temperature gives nido-2 >-(Z, ... [Pg.241]

By the use of certain additives which divert or moderate the degradation reaction. A wide range of antioxidants and stabilisers function by this mechanism (see Chapter 7). [Pg.97]

It is an observed fact that heating PVC at temperatures above 70°C has a number of adverse effects on the properties of the polymer. At processing temperatures used in practice (150-200°C) sufficient degradation may take place during standard processing operations to render the product useless. It has been found that incorporation of certain materials known as stabilisers retards or moderates the degradation reaction so that useful processed materials may be obtained. [Pg.325]

In addition to stabilisers, antioxidants and ultra-violent absorbers may also be added to PVC compounds. Amongst antioxidants, trisnonyl phenyl phosphite, mentioned previously, is interesting in that it appears to have additional functions such as a solubiliser or chelator for PVC insoluble metal chlorides formed by reaction of PVC degradation products with metal stabilisers. Since oxidation is both a degradation reaction in its own right and may also accelerate the rate of dehydrochlorination, the use of antioxidants can be beneficial. In addition to the phenyl phosphites, hindered phenols such as octadecyl 3-(3,5-di-tcrt-butyl-4-hydroxyphenyI)propionate and 2,4,6-tris (2,5-di-rcrt-butyl-4-hydroxybenzyl)-1,3,5-trimethylbenzene may be used. [Pg.330]

PET suitable for bottle manufacture is produced by a modified process. Here the high-viscosity polymer melt is subjected to a rapid quenching in water to produce clear amoiphous pellets. These are further polymerised in the solid phase at temperatures just below the T . This is useful to reduce aldehyde content, since aldehyde-forming degradation reactions occur less in the lower temperature solid phase polymerisations. Aldehydes can impart a taste to beverages and it is important to keep the aldehyde content to below 2.5 p.p.m. [Pg.718]

Fig. 15. Free radical induced oxidative degradation reactions. Fig. 15. Free radical induced oxidative degradation reactions.
The most common catalyst used in urethane adhesives is a tin(lV) salt, dibutyltin dilaurate. Tin(IV) salts are known to catalyze degradation reactions at high temperatures [30J. Tin(II) salts, such as stannous octoate, are excellent urethane catalysts but can hydrolyze easily in the presence of water and deactivate. More recently, bismuth carboxylates, such as bismuth neodecanoate, have been found to be active urethane catalysts with good selectivity toward the hydroxyl/isocyanate reaction, as opposed to catalyzing the water/isocyanate reaction, which, in turn, could cause foaming in an adhesive bond line [31]. [Pg.771]

The study of enzymes is important because every syndietic and degradation reaction in all living cells is controlled and catalyzed by specific enzymes. Many of these reactions are the soluble enzyme-soluble substrate type and are homogeneous in the liquid phase. [Pg.21]

The predominant activity in the study of enzymes has been in relation to biological reactions. This is because specific enzymes have bodi controlled and catalyzed syndietic and degradation reactions in all living cells. Many of diese reactions are homogeneous in the liquid phase (i.e., type 3 reactions). [Pg.832]

Cluster-expansion and cluster-degradation reactions are a feature of many polyhedral borane species. Examples of cluster-expansion are " ... [Pg.159]

Conversely, cluster degradation reactions lead to more open structures, e.g. ... [Pg.183]

Amine oxides 2, which can be prepared by oxidation of amines 1, react upon heating to yield an olefin 3 and a hydroxylamine 4. This reaction is called the Cope elimination reaction,and as a synthetic method is a valuable alternative to the Hofmann degradation reaction of quaternary ammonium salts. [Pg.64]

The radiation chemistry has been mainly discussed in terms of degradation reactions (as above) involving the loss of gaseous products and the irreversible change of the stoichiometry [203]. However, more recent results showed that polymers irradiated with radiation deposit-... [Pg.56]


See other pages where Reactions degradative is mentioned: [Pg.246]    [Pg.550]    [Pg.328]    [Pg.220]    [Pg.258]    [Pg.426]    [Pg.226]    [Pg.272]    [Pg.295]    [Pg.296]    [Pg.365]    [Pg.523]    [Pg.261]    [Pg.280]    [Pg.338]    [Pg.424]    [Pg.158]    [Pg.340]    [Pg.15]    [Pg.430]    [Pg.437]    [Pg.437]    [Pg.13]    [Pg.328]    [Pg.544]    [Pg.295]    [Pg.162]    [Pg.318]   
See also in sourсe #XX -- [ Pg.220 ]




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1,4-Polybutadiene reactions, degradation

Alkaline degradation dehydration reactions

Alkaline degradation reactions

Alkaline degradation reactions, control

Aspartame degradation reaction

Bacterial Degradation via Indole. The Tryptophanase Reaction

Browning reaction degradation products

Caramelization degradation reactions

Carbohydrate degradation, reaction routes

Carboranes degradation reactions

Chemical Reactions, Degradation, and Erosion

Degradation Mechanisms Basic Reactions in Water

Degradation Reaction Mechanisms - Criado Method

Degradation chain reaction

Degradation dehydration reaction

Degradation modelling hydrolysis reaction

Degradation oxidative reactions

Degradation reaction mechanisms

Degradation reactions Edman

Degradation reactions, photodegradation

Degradations, oxidation reactions

Degradative chemical reactions

Degradative reactions, ozonolysis

Diffusion controlled reactions in polymer degradation

Durability degradation reactions

Edman degradation Ugi reaction

Elimination Reactions- Ligand Degradation

Enzyme degradation reactions

Free radical reactions oxidative degradation

Group degradative reaction

Hofmann Degradation A Chain-Shortening Reaction

Hofmann degradation reaction

Hydrolysis, Alcoholysis, Thermolysis, and Degradation Reactions

Interfacial degradation reactions

Interfacial degradation reactions materials

Intestinal drug degradation reactions

Kinetic Degradation and Reaction Mechanisms in the Solid State of Natural Fibers

Maillard reaction amino acid Strecker degradation

Maillard reaction. Amadori compound Strecker degradation

Mechanism of degradation reaction

Mineral Reactions, Passivation and Degradation Rates

Molecular rearrangement reactions, thermal degradation

Nonoxidative Thermal Degradation Reactions

Oxidation and degradation reactions

Peeling reactions, alkaline degradation

Peptides degradation reactions

Phenol degradation reaction

Polyacrylonitrile degradation reaction

Polymer degradation, photosensitized reactions

Polypropylene degradation reactions

Reaction E Strecker Degradation

Reaction degradation

Reaction degradation

Reaction homogeneous degradation

Reaction kinetics, degradation

Reaction with thermal degradation

Reaction-diffusion degradation model

Reactions of Hydroperoxide Species That Lead to Backbone Degradation

Rearrangement reactions Hofmann degradation

Rubber-degrading reaction

Starch degradation reactions

Step-reaction polymers, thermal degradation

Steroid degradation reactions

Strecker degradation reaction

Strength bond, degradation reactions

Temperature, reaction degradation

The Chemical Reactions of DNA Damage and Degradation

The Primary Redox-Reactions Degradation of Organic Matter

Thermal degradation, reactions

Thermo-oxidative degradation, reactions

Vitamin degradation reaction

Von Braun amide degradation Ritter reaction

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