Ultimate degradation

Details of the hydrolytic process are somewhat more complicated because the acid-catalyzed hydrolysis proceeds via the initial protonation of an alkoxy oxygen followed by bond cleavage. Because the protonation can involve the exocyclic or endocyclic alkoxy group, two different sets of initial products are possible. However, in both cases the ultimate degradation products remain the same. These two possible reaction paths are shown on page 130. 

Abiotic hydrolysis generally accomplishes only a single step in the ultimate degradation of the compounds that have been used for illustration. The intervention of snbseqnent biotic reactions is therefore almost invariably necessary for their complete mineralization. 

Extracts of Flavobacterium heparinum that had been induced to grow on heparin-like polysaccharides contain a number of enzymes that may ultimately degrade heparin and heparan sulfate to monosaccharides.137,145 240 The enzymes that cause the primary cleavage of heparinlike chains are heparinase (EC 4.2.2.7) and heparanase (EC 4.2.2.8, formerly called heparitinase241,242). 

Resistance of an elastomer to swelling and ultimate degradation due to contact with or immersion in an oil. 

Simulation test on the ultimate degradation in surface water... 

Taking into consideration its physico-chemical properties, removal efficiencies, low biodegradability, predicted environmental levels, toxicity, and the need to provide sufficient safety margins for aquatic organisms, the demand for alternative cationic surfactants arose. Since 1991, DTDMAC has been replaced in some European countries due to producer s voluntary initiatives with new quaternary ammonium compounds, the esterquats. These contain an ester function in the hydrophobic chain (Table 1.3) that can be easily cleaved, releasing intermediates that are susceptible to ultimate degradation [24-26]. The effects of the phasing-out and replacement of DTDMAC can be demonstrated by the results of a Swiss study, where the surfactant... 

Alcohol ether sulfates. Ready aerobic biodegradation of AESs has been described [113], with co/(3-oxidation and cleavage of the sulfate and ether bonds attributed to the process [10]. However, molecular oxygen is not necessary for the two latter steps, and primary and ultimate degradation has been described under both aerobic and anaerobic conditions [114]. 

The available data summarised in this review support previous conclusions that trisiloxane silicone surfactants should be relatively benign in the natural environment. Primary degradation is rapid and ultimate degradation to naturally occurring compounds, i.e. C02, H20 and Si(OH)4, is indicated, though not yet demonstrated unequivocally. 

Acetate is known to be a good carbon source for fungi and would be expected to be the ultimate degradation product of cutin (14). The effect of acetate on the production of cutinase by the T-8 strain of F. solani was examined and compared with that of glucose. Since previous studies showed that hydrolysis of the artificial substrate p-nitrophenylbutyrate, PNB, was specifically hydrolyzed by cutinase in the T-8 strain, this activity was used to measure cutinase levels (8). Figure 1 illustrates that basal levels of cutinase activity were detected in the growth medium when T-8 was grown on... 

Since all condensed phosphates are ultimately degraded to monophosphate in hot solution, especially at low pH, the total phosphorus(V) content of a substance may readily be determined after hydrolysis either gravimetrically or titrimetrically (109). However, as soon as it is a question of estimating the content of separate components in mixtures of condensed phosphates insuperable difficulties are encountered if methods depending on precipitation, titration, or a combination of the two are used. Even a quantitative precipitation of monophosphate is impossible if polyphosphates with chain length of n = 3 or more arc present in the solution. The precipitating cation and the compound to be precipitated by it are partly kept in solution by the polyphosphate part of the polyphosphate is also carried down by the precipitate. Both of these effects depend in their extent in different ways on the nature and quantity of the substances present and the analysis gives a correct quantitative result only in isolated instances... 

Thus, the degradative oxidation of chlorophenols proceeds by a hydroxy-lated species (Equation 6.99 and Equation 6.100), followed by ring opening to yield aldehydes and ultimate degradation of C02 and CP. It was suggested that the first step is the formation of radical cation by acid-catalyzed dehydration of radicals formed due to the interaction of OH with chlorophenols. 

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