Kinetics of hydrolysis

S. N. Misra and G. H. Cady, Kinetics of Hydrolysis of Oyygen Dfluoride, Report No. TR-70, University of Washington Department of Chemistry, Seattle, Jan. 1972. 

The kinetics of hydrolysis reactions maybe first-order or second-order, depending on the reaction mechanism. However, second-order reactions may appear to be first-order, ie, pseudo-first-order, if one of the reactants is not consumed in the reaction, eg, OH , or if the concentration of active catalyst, eg, reduced transition metal, is a small fraction of the total catalyst concentration. 

Hydrolysis and Polycondensation. As shown in Figure 1, at gel time (step C), events related to the growth of polymeric chains and interaction between coUoids slow down considerably and the stmcture of the material is frozen. Post-gelation treatments, ie, steps D—G (aging, drying, stabilization, and densification), alter the stmcture of the original gel but the resultant stmctures aU depend on the initial stmcture. Relative rates, of hydrolysis, (eq. 2), and condensation, (eq. 3), determine the stmcture of the gel. Many factors influence the kinetics of hydrolysis and... 

A comparison of the kinetics of hydrolysis and isotopic exchange of amides A and B was carried out. Some of the data are given below. An interesting observation is that there is more C=0 exchange for A than for B. From this observation, and other data given, develop a stepwise mechanism for the hydrolysis of each amide and a qualitative comparison of the substituent effects on the various steps. 

Mechanistic studies are particularly needed for the hydrolysis and polymerization reactions that occur in sol-gel processing. Currently, little is known about these reactions, even in simple systems. A short list of needs includes such rudimentary data as the kinetics of hydrolysis and polymerization of single alkoxide sol-gel systems and identification of the species present at various stages of gel polymerization. A study of the kinetics of hydrolysis and polymerization of double alkoxide sol-gel systems might lead to the production of more homogeneous ceramics by sol-gel routes. Another major area for exploration is the chemistry of sol-gel systems that might lead to nonoxide ceramics. 

Capacitance measurements of phospholipid monolayers at the ITIES have been proposed as a suitable tool for studying the enzyme activity under the precise control of the electrical state of the monolayer [81]. Kinetics of hydrolysis of phosphatidylcholine... 

Hydrolysis of oximes catalyzed by transition-metal complexes has not been studied prior to a report by Kostic et al. They have reported kinetics of hydrolysis of acetoxime to acetone catalyzed by two palladium(II) complexes, identified active species in the hydrolysis reaction, proposed a reaction mechanism, and fully characterized a bis(acetoxime) complex that is relatively stable toward hydrolysis.458... 

Yoshioka, T Motoki, T. and Okuwaki, A., Kinetics of hydrolysis of poly(ethylene terephthalate) powder in sulfuric acid by a modified shrinking-core model, Ind. Eng. Chem. Res., 40, 75-79 (2001). 

Serine peptidases can hydrolyze both esters and amides, but there are marked differences in the kinetics of hydrolysis of the two types of substrates as monitored in vitro. Thus, the hydrolysis of 4-nitrophenyl acetate by a-chy-motrypsin occurs in two distinct phases [7] [22-24]. When large amounts of enzyme are used, there is an initial rapid burst in the production of 4-nitro-phenol, followed by its formation at a much slower steady-state rate (Fig. 3.7). It was shown that the initial burst of 4-nitrophenol corresponds to the formation of the acyl-enzyme complex (acylation step). The slower steady-state production of 4-nitrophenol corresponds to the hydrolysis of the acetyl-enzyme complex, regenerating the free enzyme. This second step, called deacylation, is much slower than the first, so that it determines the overall rate of ester hydrolysis. The rate of the deacylation step in ester hydrolysis is pH-dependent and can be slowed to such an extent that, at low pH, the acyl-enzyme complex can be isolated. 

G. M. Blackburn, J. D. Plackett, Strain Effects in Acyl Transfer Reactions. Part I. The Kinetics of Hydrolysis of Some N-Aryl-Lactams , J. Chem. Soc., Perkin Trans. 2 1972, 1366-1371. 

Like in Chapt. 7, we begin the discussion with acetates, since acetic acid is the simplest nontoxic acyl group, formic acid being less innocuous. An informative study was carried out to compare the kinetics of hydrolysis of two types of corticosteroid esters, namely methyl steroid-21-oates (which are active per se) and acetyl steroid-21-ols (which are prodrugs), as exemplified by methyl prednisolonate (8.69) and prednisolone-21-acetate (8.70), respectively [89]. In the presence of rat liver microsomes, the rate of hydrolytic inactivation of methyl steroid-21-oates was much slower than the rate of hydrolytic activation of acetyl steroid-21-ols. Thus, while the Km values were ca. 0.1 -0.3 mM for all substrates, the acetic acid ester prodrugs and the methyl ester drugs had Vmax values of ca. 20 and 0.15 nmol min-1 mg-1, respectively. It can be postulated that the observed rates of hydrolysis were determined by the acyl moiety, in other words by the liberation of the carboxylic acid from the acyl-enzyme intermediate (see Chapt. 3). 

Nitrobenzoylamino)-2,2-dimethylpropanamide (143 R = Me) reacts in methanol-DMSO solution with sodium methoxide to yield 5,5-dimethyl-2-(4-nitrophenyl)imidazol-4(5//)-one (144 R = Me). The 4-methoxyphenyl derivative and the parent phenyl derivative react similarly, as do compounds in which variation of the 2-substitutent (R = Pr , Ph, 4-O2NC6H4) was made. The mechanism of the cyclization probably involves initial formation of the anion of the alkanamide (145), which adds to the carbonyl group of the benzamido moiety to yield the tetrahedral oxyanion (146) proton transfer and dehydration then yield the heterocycle (144). The kinetics of hydrolysis in water at 70 °C and pH 2-11 of A-glycidylmorpholine (147) have been reported. ... 

Adewuyi, Y.G. and Carmichael, G.R. Kinetics of hydrolysis and oxidation of carbon disulfide by hydrogen peroxide in alkaline medium and application to carbonyl sulfide, Environ. Sci. Technol, 21(2) 170-177, 1987. 

Khan, S.U. Kinetics of hydrolysis of atrazine in aqueous fulvic acid solution, Pestle. Sci, 9(l) 39-43, 1978. 

Information on the linkage requirements (for arabinofuranosidase) and the subsite binding requirements of em/o-arabinanase was obtained by studying the kinetics of hydrolysis of 1,5-a-L-arabino-oligosaccharides (compared to beet arabinan) and by characterising the structures of the branched arabino-oligosaccharides produced by endo-arabinanase hydrolysis of partiaUy debranched beet arabinan. With arabinofuranosidase, the rates of hydrolysis of... 

Investigation of the kinetics of hydrolysis of aldicarb and other carbamate pesticides under a variety of conditions in solution. 

The kinetics of hydrolysis of the sulfone of 3,7-dibenzothiophendi-sulfonyl chloride have been investigated in a 70% dioxane-water mixture. Hydrolysis rates were measured both conductometrically and titrimetrically. 

A number of points should be considered to determine the most appropriate experimental conditions for the desired reaction and, to that end, the kinetics of hydrolysis and ionization of 4-methyl-2-phenyl-, 4-benzyl-2-phenyl-, and 4-benzyl-2-methyl-5(4//)-oxazolones have been investigated. Deprotonation of 5(477)-oxazolones in aqueous media, which leads to racemization of optically active 5(477)-oxazolones, is a fast process that competes with the ring opening. The difference between the rate constant for racemization and the ring opening is greater in solvents with dielectric constants less than water and thus, oxazolones racemize faster than they hydrolyze. 

Activation of a-D-mannosidase from the limpet by Zn2+ and Cl-provides a particularly good example of the ways in which the kinetics of hydrolysis may be altered. Fig. 2 shows the effect of Zn2+, Cl-, or both, on the velocity of hydrolysis of substrate at varying concentration. Inspection of die curves reveals that Zn2+ increases the affinity of the enzyme for the substrate (competitive type of effect), whereas the main effect of Cl- is to increase the rate of hydrolysis (non-competitive effect). 

Synthesis and Kinetics of Hydrolysis of 3,5-Dimethyl-N-acetyl-p-benzoquinone Imine 235... 

Micelles in the Physical Chemistry Laboratory. Kinetics of Hydrolysis of 5,5 -Dithiobis-(2-nitrobenzoate) 246... 

Figure 9.7 Different degrees and kinetics of hydrolysis of structurally closely related 3-lactams [114].

Klausen, J., M. A. Meier, and R. P. Schwarzenbach, Assessing the fate of organic contaminants in aquatic environments Mechanism and kinetics of hydrolysis of a carboxylic ester , J. Chem. Educ., 74, 1440-1444 (1997). 

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