Kinetics 1955 hydrolysis

Fr kjaer et al., 1984 Grit et al., 1989). An example of the pH dependency on the hydrolysis rate of liposomes consisting of soybean phosphatidylcholine is presented in Fig. 6. Hydrolysis kinetics changed rather abruptly around the phase transition temperature. 

Perdue EM, NL Wolfe (1982) Modification of pollutant hydrolysis kinetics in the presence of humic substances. Environ Sci Technol 16 847-852. 

Although the Lewis cell was introduced over 50 years ago, and has several drawbacks, it is still used widely to study liquid-liquid interfacial kinetics, due to its simplicity and the adaptable nature of the experimental setup. For example, it was used recently to study the hydrolysis kinetics of -butyl acetate in the presence of a phase transfer catalyst [21]. Modeling of the system involved solving mass balance equations for coupled mass transfer and reactions for all of the species involved. Further recent applications of modified Lewis cells have focused on stripping-extraction kinetics [22-24], uncatalyzed hydrolysis [25,26], and partitioning kinetics [27]. 

In our previous work [63], we studied the hydrolysis kinetics of lipase from Mucor javanicus in a modified Lewis cell (Fig. 4). Initial hydrolysis reaction rates (uri) were measured in the presence of lipase in the aqueous phase (borate buffer). Initial substrate (trilinolein) concentration (TLj) in the organic phase (octane) was between 0.05 and 8 mM. The presence of the interface with octane enhances hydrolysis [37]. Lineweaver-Burk plots of the kinetics curve (1/Uj.] = f( /TL)) gave straight lines, demonstrating that the hydrolysis reaction shows the expected kinetic behavior (Michaelis-Menten). Excess substrate results in reaction inhibition. Apparent parameters of the Michaelis equation were determined from the curve l/urj = f /TL) and substrate inhibition was determined from the curve 1/Uj.] =f(TL) ... 

The UV-spectra of azolides have already been discussed in the context of hydrolysis kinetics in Chapter 1. Specific infrared absorptions of azolides were mentioned there as well increased reactivity of azolides in nucleophilic reactions involving the carbonyl group is paralleled by a marked shift in the infrared absorption of the corresponding carbonyl bond toward shorter wavelength. For example, for the highly reactive N-acetyl-tetrazole this absorption is found in a frequency range (1780 cm-1) that is very unusual for amides obviously the effect is due to electron attraction by the heterocyclic sys-tem.[40] As mentioned previously in the context of hydrolysis kinetics of both imidazo-... 

Then the modelization of the hydrolysis kinetics requires at each time the knowledge of a and N. a can be calculated by writing the different relations of dissociation equilibria of water,polyacid and NH3 (produced by the hydrolysis reaction). We have proposed to determine at each reaction step and simulate the whole kinetics by using a Monte-Carlo method. (see ref.8 ). 

In Figure 1 we compare the calculated and measured variations of t for a copolymer of initial r - 17%. Let us remark that in these experiments, the pH has not been adjusted at a constant value and the hydrolysis process induces a change of pH in the solution. We have taken into account this effect in our calculations. In fig.2, we give the predicted hydrolysis kinetics for the same polymer sample but in the case where pH remains constant. 

Figure 1. Calculated and experimental ( ) hydrolysis kinetics Copolymer C, T=80°C, different initial pH...

Figure 2. Calculated hydrolysis kinetics for Copolymer C at 80°C at different constant pH...

Serratrice et al., studied the hydrolysis kinetics of the iron(III) complexes of the tripodal hexadentate siderophore mimics, O-TRENSOX (26) and TRENCAMS, and their heteropodal analogs, TRENSOX2CAMS and TRENSOXCAMS2 (176). Protonation of the complexes proceeds in four stages (i) the initial... 

RP-HPLC found application in the monitoring of the alkali hydrolysis kinetics of alkali-clearable azo disperse dyes containing a fluorosulphonyl group. The chemical structures of dyes included in the experiments are shown in Fig. 3.85. Samples for RP-HPLC analysis were neutralized to pH 4.0 - 4.5 with diluted HC1 mixed with five volumes of ACN and injected without any other sample preparation step. Separation was carried out in an ODS column at ambient temperature. The isocratic mobile phase consisted of ACN-water (80 20, v/v) and dyes were detected at their absorption maxima. HPLC measurements indicated that dyes are easily hydrolysed under relatively mild alkaline conditions, and the hydrolysis follows a pseudo first-order kinetics [148],... 

The effect of various experimental conditions on the alkali-hydrolysis kinetics of 4-amino-4 -fluorosulphonylazo benzene disperse dyes was investigated by RP-HPLC. 

J. Koh, Alkali hydrolysis kinetics of alkali-clearable azo disperse dyes containing a fluorosulpho-nyl group and their fastness properties on PET/cotton blends. Dyes Pigm., 64 (2005) 17-23. 

J. Koh, A.J. Greaves and J.P. Kim, Alkali-hydrolysis kinetics of 4-amino-4 -fluorosulfonyla-zobenzene disperse dyes and their dyeing fastness properties. Dyes Pigm., 60 (2004) 155-165. 

J. Koh and A.J. Greaves, Synthesis and application of an alkali-clearable azo disperse dye containing a fluorosulfonyl group and analysis of its alkali-hydrolysis kinetics. Dyes Pigm., 50 (2001) 117-126. 

In conditions where much higher concentrations of DHS are possible (i. e., in sewage sludge or in sediment/soil interstitial water), the impact of DHS on organic pollutant hydrolysis kinetics was predicted to be larger. 

The next example is 1,3-dibenzoylurea (4.222), a diacetylated linear urea. The hydrolysis kinetics and enzymatic cleavage of 1,3-dibenzoylurea together with various other /V-acylbenzamides were studied to assess the suitability of these compounds as prodrugs for the amido group [113]. At pH 7.4 and 37°, 1,3-dibenzoylurea was hydrolyzed quantitatively to benzoic acid and N-benzoylurea (4.223) with a tm value of 39 h. Since the hydrolysis of 1,3-di-benzoylurea was not catalyzed by human plasma, it was concluded that the acyclic diureide structure is not appropriate in prodrug design. 

D. Visky, M. Kraszni, S. Hosztafi, B. Noszal, Species-Specific Hydrolysis Kinetics of A-Methylated Heroin Derivatives , Helv. Chim. Acta 2000, 83, 364-372. 

H. Bundgaard, A. Buur, V. H. L. Lee, Timolol Prodrugs Preparation and Hydrolysis Kinetics of A-Benzoyl Carbamate Esters of Timolol and Related Compounds , Acta Pharm. Suec. 1988, 25, 293 - 306. 

A. Buur, H. Bundgaard, E. Falch, Prodrugs of 5-Fluorouracil. IV. Hydrolysis Kinetics, Bioactivation and Physicochemical Properties of Various N-Acyloxymethyl Derivatives of 5-Fhiorouracil , Int. J. Pharm. 1985, 24, 43 - 60. 

H. Bundgaard, G. J. Rasmussen, Prodrugs of Peptides. 11. Chemical and Enzymatic Hydrolysis Kinetics of N-Acyloxymethyl Derivatives of a Peptide-Like Bond , Pharm. Res. 1991, 8, 1238-1242. 

Recently reported results for the hydrolysis kinetics of chlorpyrifos (7 ) suggest that equation 2 may not be a valid representation of alkaline hydrolysis kinetics for at least one class of pesticides (organophosphorothioates). In short, kg may be pH dependent. However, disappearance kinetics for such molecules are still adequately described at fixed pH by pseudo first-order kinetics. 

Acid-catalyzed hydrolysis kinetics are described by the expression... 

Though this system is perhaps an extreme example of slow sorption kinetics, it illustrates that the assumption of rapid equilibrium between the sediment and aqueous phases is questionable. The importance of such an observation to the investigation of hydrolysis kinetics in sediment/water systems must be emphasized. Certainly, any model of hydrolysis kinetics in sediment/water systems must include explicit expressions for the kinetics of the sorption/desorption process. 

First, determination of hydrolysis kinetics for each compound in sediment-free distilled, buffered distilled or natural water systems were measured. Using sterile techniques, concentrations of the parent compounds were determined as a... 

Neutral Hydrolysis Studies. Investigations of neutral (pH-independent) hydrolysis kinetics in sediment/water systems were conducted for three organophosphorothioate insecticides (chlorpyrifos, diazinon and Ronnel), 4-(p-chlorophenoxy)butyl bromide, benzyl chloride, and hexachlorocyclopentadiene. 

Alkaline Hydrolysis Studies. Alkaline catalyzed hydrolysis kinetics in sediment/water systems have been investigated for chlorpyrifos and the methyl and n-octyl esters of 2,4-dichlorophenoxyacetic acid (2,4-D). 

Chlorpyrifos. As was the case for the neutral hydrolysis studies, the most detailed kinetic investigations of alkaline hydrolysis kinetics in sediment/water systems have been conducted using chlorpyrifos (10). As can be seen from Figure 2, alkaline hydrolysis of chlorpyrifos is not second-order, so the value selected for k cannot be calculated from the pH and a second-order rate constant. Nevertheless, since aqueous kinetics at alkaline pH s for chlorpyrifos was always pseudo-first order, careful pH measurements and Figure 2 can be used to select accurate values for k at any pH. 

Base hydrolysis kinetic data are reported for ppb solutions of carbofuran,3-OH carbofuran, methomyl and oxamyl. The results are compared with those reported previously for aldicarb, aldlcarb sulfoxide, and aldicarb sulfone. Second order reaction rate constants, k, have been calculated and range from 169 liter mln mole for oxamyl to 1.15 liter mln mole for aldicarb. The order for rate of base hydrolysis is as follows oxamyl >3-hydroxycarbofuran >aldicarb sulfone v- carbofuran >aldicarb sulfoxide > methomyl -v aldicarb. The activation energy for the base hydrolysis of carbofuran was measured to be 15.1 +0.1 kcal mole , and is similar to the value previously reported for aldicarb sulfone. Rapid detoxification of aldicarb, a representative oxime carbamate pesticide, by in situ hydrolysis on reactive ion exchange beds is reported. 

Structures have been determined for [Fe(gmi)3](BF4)2 (gmi = MeN=CHCF[=NMe), the iron(II) tris-diazabutadiene-cage complex of (79) generated from cyclohexanedione rather than from biacetyl, and [Fe(apmi)3][Fe(CN)5(N0)] 4F[20, where apmi is the Schiff base from 2-acetylpyridine and methylamine. Rate constants for mer fac isomerization of [Fe(apmi)3] " were estimated indirectly from base hydrolysis kinetics, studied for this and other Schiff base complexes in methanol-water mixtures. The attenuation by the —CH2— spacer of substituent effects on rate constants for base hydrolysis of complexes [Fe(sb)3] has been assessed for pairs of Schiff base complexes derived from substituted benzylamines and their aniline analogues. It is generally believed that iron(II) Schiff base complexes are formed by a template mechanism on the Fe " ", but isolation of a precursor in which two molecules of Schiff base and one molecule of 2-acetylpyridine are coordinated to Fe + suggests that Schiff base formation in the presence of this ion probably occurs by attack of the amine at coordinated, and thereby activated, ketone rather than by a true template reaction. ... 

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