Acid hydrolysis constants

Table III. Acid Hydrolysis Constants for Various Cellulosic Materials...

TABLE 1.5 Acid Hydrolysis Constants (pAas) for Some Aquo Ions and Complex Metal Ions at 25 °C (Selected from Basolo and Pearson,22 and pH Precipitation Ranges of Hydroxides or Hydrous Oxides (Adapted from Walton23)... 

Acid Hydrolysis Constants (pK s) for Some Aqua Ions at 298 K and pH Precipitation Range of Hydroxides or Hydrous Oxides... 

Base-catalyzed hydrolysis in PET is important for fiber manufacture, because both organic and inorganic bases are used for dyeing, subsequent treatment, and during washing. The rate constant for base-catalyzed hydrolysis of dibasic esters is smaller than the acid hydrolysis constant, resulting in a higher stability of PET fibers in alkaline solutions than in acid solutions. 

The acid hydrolysis constant of trioxane, as determined by Skrabal, Stockmair and Schreinei at -arious temperatures in the presence of A p-toluene sulfonic acid, is shown below ... 

K2 is called the hydrolysis constant for sodium ethanoate. Hydrolysis occurs when salts involving weak acids or bases are dissolved in water. It is often also found with metal ions in solution. The ion [M(H20) ] dissociates to the hydroxy species [M(H20) , (OH)]f 1. ... 

Double Polarization. The Clerget double polarization method is a procedure that attempts to account for the presence of interfering optically active compounds. Two polarizations are obtained a direct polarization, followed by acid hydrolysis and a second polarization. The rotation of substances other than sucrose remains constant, and the change in polarization is the result of inversion (hydrolysis) of the sucrose. 

Fig. 4.2. Conelation of acid dissociation constants of benzoic acids with rates of alkaline hydrolysis of ethyl benzoates. [From L. P. Hammett, J. Am. Chem. Soc. 59 96 (1937).]...

The hydrolysis constant is thus related to the ionic product of water and the ionisation constant of the acid. Since Ka varies slightly and Kw varies considerably with temperature, Kh and consequently the degree of hydrolysis will be largely influenced by changes of temperature. 

The species [organohn(IV)] (n — 1-3) are considered to be Lewis acids of different strength, depending on the groups bound to the tin atom. As a consequence, they promptly hydrolyze in aqueous solution, as first demonstrated by Tobias. Later studies on the interactions of [MeiSndV)] " with hgands containing different donor atoms ( O, N, S, etc.) necessitated determination of the hydrolysis constants the evaluation of such complex formation constants was based on the data obtained earlier from independent measurements. Some data are compared in Table 1. 

In 1961, Roig and Dodson carried out a further study of the exchange in perchlorate media under identical conditions (25 °C, fi = 3.0 M) to those in the Tl(III) hydrolysis studyThe isotope was used, with a separation procedure based on extracting TI(III) from reaction mixtures with either methyl isobutyl ketone or diethyl ether. The exchange was examined in the absence of light, and a correction procedure to eliminate the catalytic effects of traces of chloride ions was used since Tl(III) concentrations of 10 M were necessary at the very low acidities employed. Using the known values of the first and second hydrolysis constants of Tl(III) (K2 and K3)... 

Considering the titration end-point or equivalence point, we in fact have to deal with the salt of a weak acid and a strong base or the reverse. Such a salt undergoes hydrolysis, e.g., for NaA, A + H20 HA + OH, so that the hydrolysis constant can be written as... 

Some compounds exhibit pH behavior in which a bell-shaped curve is obtained with maximum instability at the peak [107]. The peak corresponds to the intersection of two sigmoidal curves that are mirror images. The two inflection points imply two acid and base dissociations responsible for the reaction. For a dibasic acid (H2A) for which the monobasic species (HA-) is most reactive, the rate will rise with pH as [HA-] increases. The maximum rate occurs at pH = (pA) + pK2)/2 (the mean of the two acid dissociation constants). Where an acid and base react, the two inflections arise from the two different molecules. The hydrolysis of penicillin G catalyzed by 3,6-bis(di-methylaminomethyl)catechol [108], is a typical example. For a systematic interpretation of pH-degradation profiles, see the review papers by van der Houwen et al. [109] and Connors [110]. 

The second termination reaction is alkyl chain end transfer from the active species to aluminium [155]. This termination becomes major one at lower temperatures in the catalyst systems activated by MAO. XH and 13CNMR analysis of the polymer obtained by the cyclopolymerization of 1,5-hexadiene, catalyzed by Cp ZrCl2/MAO, afforded signals due to methylenecyclopentane, cyclopentane, and methylcyclopentane end groups upon acidic hydrolysis, indicating that chain transfer occurs both by /Miydrogen elimination and chain transfer to aluminium in the ratio of 2 8, and the latter process is predominant when the polymerization is carried out at — 25°C [156]. The values of rate constants for Cp2ZrCl2/MAO at 70°C are reported to be kp = 168-1670 (Ms) 1, kfr = 0.021 - 0.81 s 1, and kfr = 0.28 s-1 [155]. 

Thereafter, the reaction between the coordinated dienoate ligand in 106 and acrylonitrile was examined (Scheme 12). Surprisingly, this reaction is complete within 56 h (pseudo-first-order rate constant k — 1.4 x 10-5 s-1, ti/2 ca. 0.5 day) and affords only two products 107a and 107b in a ratio of 57 43 (or the correepsonding acids 103a,b via acid hydrolysis). Thus, in... 

The mathematical relationship between ATa, the ionization constant for a weak acid, and Kb, the base hydrolysis constant for the anion of the weak acid is = ATa x Kt,. 

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. 

Alternatively one could suggest that a micellized sulfuric or sulfonic acid is not strong. For example, apparent acid dissociation constants of weak acids decrease when the acids are bound to anionic micelles (Hartley, 1948), and the rapid hydrolysis of micellized alkyl sulfates at low pH is consistent with... 

S. Kobayashi, S. Nagayama, T. Busujima, Lewis Acid Catalysts Stable in Water. Correlation between Catalytic Activity in Water and Hydrolysis Constants and Exchange Rate Constants for Substitution of Inner-Sphere Water Ligands J. Am. Chern. Soc 1998, 120, 8287-8288. 

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