Hydrolysis ethyl acetate

Specific rate coefficients (related to unit amount of acid centres) were approximately the same for solid catalysts as well as for HC1 [474]. However, when a montmorillonite clay activated by adsorption of protons on its surface was used as the catalyst in ethyl acetate hydrolysis [475], a higher specific rate coefficient (about 1.8 times at 25°C) was found for the reaction catalysed by adsorbed protons than by dissolved acid, this result being explained by the authors by an increase of activation entropy in the former case. 

This sieve effect cannot be considered statically as a factor that only determines the amount of accessible acid groups in the resin in such a way that the boundary between the accessible and non-accessible groups would be sharp. It must be treated dynamically, i.e. the rates of the diffusion of reactants into the polymer mass must be taken into account. With the use of the Thiele s concept about the diffusion into catalyst pores, the effectiveness factors, Thiele moduli and effective diffusion coefficients can be determined from the effect of the catalyst particle size. The apparent rates of the methyl and ethyl acetate hydrolysis [490] were corrected for the effect of diffusion in the resin by the use of the effectiveness factors, the difference in ester concentration between swollen resin phase and bulk solution being taken into account. The intrinsic rate coefficients, kintly... 

Effect of diffusion and adsorption in methyl and ethyl acetate hydrolysis in water at 40°C... 

Fig. 20. Effect of degree of crosslinking (% DVB) of a standard ion exchanger on the diffusivities, Def (cm2 min-1), and the selectivity ratio, S = efs/ efAc ( ef = effective rate coefficient, S = sucrose, Ac = ethyl acetate). Data were obtained by rate measurements and Wheeler—Thiele analysis of simultaneous sucrose and ethyl acetate hydrolysis at 70°C [508],...

Methods for determining MBBC residues in plant tissues involve isolation of the residue by extraction with ethyl acetate, hydrolysis of the extracted residue to 2-aminobenzimidazole, and final determination by HPLC using fluorimetric detection (37). TBZ is also determined by a similar procedure, without hydrolysis. The sensitivities of these methods are 0.02 ppm for benomyl and 0.001 ppm for TBZ. Recoveries of these compounds from various plant tissues were 90.5-102.9% for MBBC and 98.2% for TBZ, respectively (37). Tribendazole was repeatedly extracted from a sample with ethyl acetate, and the combined extract was evaporated under reduced pressure below 40°C to a small volume. Subsequently, 0.1 M HC1 was added, and the evaporation was... 

The rate of the reaction depends on the pH of the solution. If it is around or higher than the p.JCa of the thiol, thiolate anion will be formed and this opens the epoxide much faster than does the unionized thiol. The nucleophile is regenerated by the oxyanion produced in the rate-determining step. A more familiar example is the base-catalysed hydrolysis of esters we have mentioned several times in this chapter. The full pH-rate profile (Chapter 13) for the hydrolysis of a simple ester such as ethyl acetate shows just two straight lines meeting each other (and zero rate) at about neutrality. Ethyl acetate hydrolysis occurs by SAC or SBC only. 

Relative reactivity of imidazole and monohydrogen phosphate tfimidazolel/iKHPOj") is order of unity for general base catalysis, but about 10 for nucleophilic catalysis This ratio is 0,25 for ethyl acetate hydrolysis and 4.7 x I0 for p-nitrophenyl acetate hydrolysis 92... 

Chemical heterogeneities present in soils, sediments, and aquifers undoubtedly have an effect on rates of pollutant degradation. Other sources of surface catalysis not discussed here include Bronsted acidity of surface sites, that become apparent as surfaces become dehydrated (El-Amamy and Mill, 1984). Surface and pore structure may play a role in the catalysis of phosmet hydrolysis by montmorillonite (Sanchez-Camazano and Sanchez-Martin, 1983) and in the catalysis of ethyl acetate hydrolysis by zeolites (Nam-ba et al., 1981). 

The dependence of m with temperature is for example m=a for dissolution of metals with acids or the action of drugs in muscles, m=cT for decompx)sition of dibromosuocinic acid, m=bT- for ethyl acetate hydrolysis with sodium hydroxide. In most of the cases m results constant, but Harcourt and Esson admitted that in some cases this does not happen, contradicting their hypothesis. 

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