Chain cleavage reaction

Contamination problems act as a barrier to the recycling of PET bottle waste. The presence of impurities that generate acid compounds at the high temperatures reached during the extrusion process prior to blow molding is a major problem in the reprocessing of PET because chain cleavage reactions are acid catalyzed. EVA... 

Spectral Dependence of the Absolute Quantum Yield of the Main Chain Cleavage Reaction... 

Side-Chain Cleavage Reactions of 0-1 and fl-O-4 Lignin Model Compounds Catalyzed by Lignin Peroxidase. 

Hydrolysis and Other Chain Cleavage Reactions 147 NMR titrations... 

Formation of pyruvate. The conversion of glucose to pyruvate requires ten enzymes (Fig. 17-7), and the sequence can be divided into four stages preparation for chain cleavage (reactions 1-3), cleavage and equilibration of triose phosphates (reactions 4 and 5), oxidative generation of ATP (reactions 6 and 7), and conversion of 3-phosphoglycerate to pyruvate (reactions 8-10). 

Figure 26 (a) The oxidation of alcohols to aldehydes via an hemiacetal intermediate (b) The sterol side chain cleavage reaction via a diol note the formation of an O-based radical intermediate... 

The free radicals may also undergo chain cleavage reactions. Low molecular weight by-products, such as water, carbon dioxide, aldehydes, ketones, and alcohols may be formed, which cause the odor and taste of the oils. The strong odor of rancid soybean oil was shown to be caused by 2-pentylfuran found in oxidized oil in storage (23). 

Polyadipamides are less thermally stable than other aliphatic polyamides because they are subject to a chain-cleavage reaction that occurs at temperatures below 300 °C. This reaction involves adipamide cyclization (Reaction 43). 

A similar side-chain cleavage reaction has been observed, under oxidative conditions, with the copper(II) and nickel(II) chelates of the Schiff base of salicyl aldehyde and an alanine ester (168). 

Important elements of sterol metabolism can also be used to elucidate where in the cell a particular precursor has moved [7]. The arrival of cholesteryl esters within lysosomes is revealed by cleavage of the fatty acid to yield free cholesterol. The subsequent transport of cholesterol to the ER can be monitored by the action of acyl-CoA cholesterol acyltrans-ferase (Chapter 14) that results in the formation of new molecular species of cholesteryl esters. In addition, sphingomyelinase treatment of the cell surface induces cholesterol movement from the plasma membrane to the ER where its arrival can likewise be monitored by the action of acyl-CoA cholesterol acyltransferase. Import of cholesterol into mitochondria (usually restricted to steroidogenic cells) can be followed by side-chain cleavage reactions that produce pregnenolone [8]. Movement of pregnenolone out of mitochondria can be followed by oxidations at positions 3, 17, and 21, which occur in the ER. 

Figure 6.31. Possible mechanisms for the final step in the cholesterol side-chain cleavage reaction, where R = the sterol nucleus and R = CH2CH2CH(CHj)j.

Random Chain Cleavage Reaction. In addition to peeling, cellulose is also reported to undergo random cleavage of glycosidic linkages in alkaline media (1,2). This reaction results in the formation of... 

Ladder polymers are also referred to as double-chain or double-strand polymers because, unlike other polymers, the backbone consists of two chains. Cleavage reactions in single-chain polymers cause a reduction in molecular weight that ultimately results in a deterioration in the properties of the polymer. For this to happen in a ladder polymer, two bonds will have to be broken in the same chain residue, which is a very unlikely occurrence. Therefore, ladder polymers usually have exceptional thermal, mechanical, and electrical properties. 

Figure 6.4 PA polymer chain cleavage reaction. Source [8],...

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