Bases hydrolysis

Principle The determination of acetylthiocholine hydrolysis, based on the absorbance at 412 nm of the yellow product - complex of thiocholine with Ellman reagent. 

Figure 9.2 Schematic prediction of strength of a polyester geotextile subjected to slow degradation by hydrolysis (based on information from [6])...

An Assay for Enzyme-Catalyzed Polyanion Hydrolysis Based on Template-Directed Excimer Formation... 

Additionally, note that base hydrolysis of hyoscyamine gives ( )-tropic acid and tropine, with racemization preceding hydrolysis. Base hydrolysis of littorine gives optically pure phenyl-lactic acid, so we deduce that hydrolysis is a more favourable process than racemization. 

The rates of hydrolysis of chelated ester species are independent of pH in the range 0-4.137,139 140 This result is expected as coordination to Co111 prevents protonation of the carbonyl oxygen and consequent acid hydrolysis. Base hydrolysis of the chelated isopropylglycine in [Co(en)2-(GlyOPr )]3+(fcoH = 1-5 x 106 M 1 s 1 at 25 °C) is about 106-fold faster than hydrolysis of the free unprotonated ester.140 The rate enhancement is entirely due to a more positive AS in the chelated ester species.140,141... 

Andrews, C. W. Fraser-Reid, B. Bowen, J. P. An ab initio study (6-31 G ) of transition states in glycoside hydrolysis based on axial and equatorial 2-methoxytetrahydropyrans. 

Hydrolysis base rate constant k < 0.9 M 1 h 1 at 25°C with a calculated t/2 > 900 yr at pH 7 (Ellington et al. 1988) Biodegradation dechlorination pseudo-first order rate constant k = 0.387 d 1 with t/2 = 1.8 d using a mixed enrichment culture derived from a contaminated estuarine sediment (Pavlostathis Prytula 2000). Biotransformation ... 

Reducing sugars dissolved by acid hydrolysis, based on O.D. weight. 

In alkaline hydrolysis, bases such as NaOH and NH3 are used for pretreatment The effects include increased porosity, larger internal surface area, a decrease of the degree of polymerization, separation of structural linkages between lignin and carbohydrates, and disruption of the lignin structure. 

If released to water, tetryl may be degraded by hydrolysis. Based on experimentally-derived pH (range of 4-9) versus rate profiles for tetryl at 40, 72, and 85 °C and a range of activation energies, the hydrolysis half-life of tetryl at 20 °C and pH 6.8 was crudely estimated to be 302 76 days. 

Calcium pumps, also termed Ca +-ATPase, are calcium channels that transport calcium from the low concentration cytoplasm to the high concentration extracellular space or ER/SR lumenal side using the energy of ATP hydrolysis. Based on their locations, calcium pumps are classified into two groups, plasma membrane Ca +-ATPase (PMCA) and sarcoplasmic reticulum Ca +-ATPase (SERCA). " Four basic isoforms of PMCA (PMCAl 4) have been identified and the other PMCA isoforms are the alternative splicing products of the basic isoforms. PMCAl and 4 are ubiquitously expressed in different tissues and PMCA2 and 3 are expressed in nerve cells. Three basic isoforms of SERCA pump and several sphcing variants have also been identified. ... 

Examples include acetal hydrolysis, base-catalyzed aldol condensation, olefin hydroformylation catalyzed by phosphine-substituted cobalt hydrocarbonyls, phosphate transfer in biological systems, enzymatic transamination, adiponitrile synthesis via hydrocyanation, olefin hydrogenation with Wilkinson s catalyst, and osmium tetroxide-catalyzed asymmetric dihydroxylation of olefins. 

Properties of PCDEs, including physicochemical ones, are not well known as the literature reviews of PCDEs have shown [4, 11,40,46]. PCDEs resemble PCBs structurally and in their chemical and physical properties, which, like PCDDs, PCDFs, and related compounds, are known to be stable and resistant to breakdown by heat, hydrolysis, bases, and acids. PCBs are also quite stable to oxidation under moderate conditions [3], but there is not much data about PCDEs concerning their stability. There is some evidence that PCDEs are resistant to bases and acids and the occurrence of PCDEs in the environment indicates that PCDEs are persistent and bioaccumulating compounds. The study of Firestone et al. [37] already showed that PCDEs are quite stable, since PCDEs could be measured in chlorophenol extracts after sulfuric acid treatment. Tetra- and octachlorinated PCDE congeners were later proven resistant in treatment with... 

The cocatalyst made by the combination of an Al-alkyl and a Lewis base is actually not a simple binary system since the two components interact chemically giving rise to new products. In the case of carboxylic esters, it has been known for a long time 56) that the reaction with Al-alkyl yields Al-alkoxides from which alcohols are obtained by hydrolysis. Based on the numerous studies conducted in the last twenty years 57 72), it is known that the reaction occurs through the preliminary formation of an acid-base complex which, thereafter, undergoes rearrangement which is more or less rapid, depending on the reaction conditions. 

A linear extrapolation to zero-time of hydrolysis based on zero-order kinetics has been used to estimate the destruction of each amino acid (Smith and Stockell, 1954 Wilcox et al. 1957). In contrast, Hirs et al. (1954) measured the destruction of amino acids in a mixture of serine, threonine, aspartic acid, and glutamic acid and showed that first-order kinetics are applicable to the destruction observed. 

Whereas base-catalyzed epimerization of 27 is faster than hydrolysis base-catalyzed hydrolysis of optically active 25 gives the corresponding P-phenyl phosphetane 1-oxide with retention of configuration The initial phosphoranes A or A, which result from a attack of hydroxide on (R)- or (S)-25, respectively, can in principle equilibrate with five diastereomeric phosphoranes, as shown in Fig. 10 for (7 )-25 However, A, C, and E are relatively high energy intermediates since a Z-butyl group is located in the a position As discussed above, racemization prior to hydrolysis requires that loss of benzyl is slow compared to pseudorotation and addition-elimination... 

Torget R, Werdene P, Hinmel M, Grohman K (1990) Appl Biochem Biotechnol 24/25 115 Schell DJ, RUey C, Walter P, Bergeron P (1990) Technical and Economic Analysis of an Enzymatic Hydrolysis Based Ethanol Plant. National Renewable Energy Laboratory proprietary draft report... 

Figure 4 shows the changes in the imide band on hydrolysis for samples of two polymers, BTDA-ODA and PMDA-ODA. The samples of BTDA-ODA underwent a rapid decrease in the imide band during the first 24-48 h of hydrolysis. The reaction then slowed markedly. Samples cured to only 300 °C have a very slightly lower initial imide content and appear to hydrolyze somewhat more rapidly than those cured to 4000 C. However, as can be seen in Table II, the percentages of imide remaining after 600 h hydrolysis, based on the final vs initial imide ratios, are the same within experimental error. 

Relation to Alkalinity. Some explanations for this behavior can be offered. Persistent levels appear to be associated with low pH (4.5-6.5) and alkalinity (<10 mg/L) in the groundwater. Residues disappeared faster from Fields 4 and 5, where pH and alkalinities were high, especially at deeper levels (Figure 5) than in Fields 1 and 2, where pH and alkalinity were low (Figure 6). Rates of chemical hydrolysis of aldicarb and its oxides have been extensively studied (26-29). Alkalinity and pH tend to increase with depth in the aquifer under all fields. However, prediction of rates of chemical hydrolysis based on known rate constants are complicated by two phenomena 1. fluctuations in groundwater... 

Base Hydrolysis Base hydrolysis is being studied as a chemical conversion method for the destruction of energetic materials. Base hydrolysis of energetic materials has been studied previously by LANL. In prior research, they have shown that 1.5 M sodium hydroxide solutions at 85° to 90°C readily break down many explosives and their PBX formulations to nonexplosive hydrolysis products. In order to understand the process and properly dispose of or treat the resulting products, a mass balance is required for the process. This requires identification and quantification of the products. 

Spatz J et al (1998) Controlled mineralization and assembly of hydrolysis-based nanoparticles in organic solvents combining polymer micelles and microwave techniques. Adv Mater 10(6) 473... 

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