Equilibrium constants for hydrolysis

It should be noted that whereas a completely soluble hydroxide (e.g. NaOH) will give a solution of high pH in which the pH will increase with concentration of the hydroxide, the pH of a solution of a sparingly soluble hydroxide will depend upon the equilibrium constant for hydrolysis and the activity of metal ions. 

Equilibrium constants for hydrolysis are quoted in Appendix 6.1 of this chapter and in Appendixes 1 and 2 at the end of the book. A still reliable source of hydrolysis constants is Baes and Mesmer (1976). 

Surface hydrolysis of metal oxide surfaces can be examined by comparison to solution equilibrium constants for hydrolysis and solubility. Indium oxide has a favorable equilibrium constant for hydrolysis [38-40] ... 

Solutions of salts may be acidic or basic because of hydrolysis of the ions. The equilibrium constant for hydrolysis equals for a cation or K/, for an anion. Calculation of the pH... 

Hammen equation A correlation between the structure and reactivity in the side chain derivatives of aromatic compounds. Its derivation follows from many comparisons between rate constants for various reactions and the equilibrium constants for other reactions, or other functions of molecules which can be measured (e g. the i.r. carbonyl group stretching frequency). For example the dissociation constants of a series of para substituted (O2N —, MeO —, Cl —, etc.) benzoic acids correlate with the rate constant k for the alkaline hydrolysis of para substituted benzyl chlorides. If log Kq is plotted against log k, the data fall on a straight line. Similar results are obtained for meta substituted derivatives but not for orthosubstituted derivatives. 

Perhaps the most extensively studied catalytic reaction in acpreous solutions is the metal-ion catalysed hydrolysis of carboxylate esters, phosphate esters , phosphate diesters, amides and nittiles". Inspired by hydrolytic metalloenzymes, a multitude of different metal-ion complexes have been prepared and analysed with respect to their hydrolytic activity. Unfortunately, the exact mechanism by which these complexes operate is not completely clarified. The most important role of the catalyst is coordination of a hydroxide ion that is acting as a nucleophile. The extent of activation of tire substrate througji coordination to the Lewis-acidic metal centre is still unclear and probably varies from one substrate to another. For monodentate substrates this interaction is not very efficient. Only a few quantitative studies have been published. Chan et al. reported an equilibrium constant for coordination of the amide carbonyl group of... 

There are a few documented examples of studies of ligand effects on hydrolysis reactions. Angelici et al." investigated the effect of a number of multidentate ligands on the copper(II) ion-catalysed hydrolysis of coordinated amino acid esters. The equilibrium constant for binding of the ester and the rate constant for the hydrolysis of the resulting complex both decrease in the presence of ligands. Similar conclusions have been reached by Hay and Morris, who studied the effect of ethylenediamine... 

Preparation and chemistry of chromium compounds can be found ia several standard reference books and advanced texts (7,11,12,14). Standard reduction potentials for select chromium species are given ia Table 2 whereas Table 3 is a summary of hydrolysis, complex formation, or other equilibrium constants for oxidation states II, III, and VI. 

The other C=N systems included in Scheme 8.2 are more stable to aqueous hydrolysis than are the imines. For many of these compounds, the equilibrium constants for formation are high, even in aqueous solution. The additional stability can be attributed to the participation of the atom adjacent to the nitrogen in delocalized bonding. This resonance interaction tends to increase electron density at the sp carbon and reduces its reactivity toward nucleophiles. 

The rates of both formation and hydrolysis of dimethyl acetals of -substituted benzaldehydes are substituent-dependent. Do you expect to increase or decrease with increasing electron-attracting capacity of the pam substituent Do you expect the Ahydroi to increase or decrease with the electron-attracting power of the substituent How do you expect K, the equilibrium constant for acetal formation, to vary with the nature of the substituent ... 

Most biological environments contain substantial amounts of divalent and monovalent metal ions, including Mg, Ca, Na, K, and so on. What effect do metal ions have on the equilibrium constant for ATP hydrolysis and the... 

Write the equilibrium constant, for the hydrolysis of creatine phosphate and calculate a value for at 25°C from the value of AG° in Table 3.3. 

Assuming that these quantities are independent of temperature, calculate the temperature at which the equilibrium constant for the hydrolysis of ATP becomes greater than 1. 

The reaction between cellulose and acrylamide was studied by quantitative, chromatographic separation of the substituted D-glucoses obtained on acid hydrolysis of the reaction product,320 followed by an analysis by Spurlin s method.249 Although, apparently, no check was made on the stability of the ethers to the conditions of hydrolysis, it might be expected that the ethers would isomerize only under basic conditions. The ratios of the relative equilibrium-constants for reaction at 0-2, 0-3, and 0-6 were 9 1 19, and these are attributable to the high, relative stability of the primary ether, together with the low reactivity of 0-3, also observed in rate-controlled reactions. 

Since the value of the equilibrium constant for the hydrolysis reaction of cyanide ion is larger than that for the hydrolysis of ammonium ion, the cyanide ion hydrolysis reaction will proceed to a greater extent. The solution of NH4CN(aq) will be basic (alkaline). 

Equilibrium composition of solutions in contact with freshly precipitated, Al(OH)3 and Fe(OH)3, calculated, using representative values for the equilibrium constants for solubility and hydrolysis equilibria. Shaded areas are approximate operating regions in water treatment practice coagulation in these systems occurs under conditions of oversaturation with respect to the metal hydroxide. 

The second relevant set of data is for the formation of the anhydride from substituted succinic acid derivatives. Equilibrium constants for the formation of the anhydride from the acid are available for the various methyl-substituted compounds (Table A.l) and the derived EM s are compared in Table 5 with those for intramolecular nucleophilic catalysis in the hydrolysis of half-esters... 

The equilibrium constant for the hydrolysis of C204 is best represented by which of the following ... 

In Figure 2.4, data for the equilibrium constants of esterification/hydrolysis and transesterification/glycolysis from different publications [21-24] are compared. In addition, the equilibrium constant data for the reaction TPA + 2EG BHET + 2W, as calculated by a Gibbs reactor model included in the commercial process simulator Chemcad, are also shown. The equilibrium constants for the respective reactions show the same tendency, although the correspondence is not as good as required for a reliable rigorous modelling of the esterification process. The thermodynamic data, as well as the dependency of the equilibrium constants on temperature, indicate that the esterification reactions of the model compounds are moderately endothermic. The transesterification process is a moderately exothermic reaction. 

As noted earlier, it is conceivable that the rate constants at each end are different however, Wegner noted that in the absence of nucleotide hydrolysis the assembly and disassembly reactions are in fact reversible. The rate constants are directly related to the equilibrium constants for protomer-polymer interactions at each end ... 

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