Bronsted catalysis law

For general acid catalysis, the relationship between the acidity of each acid present and the rate constant of the reaction is given by the Bronsted catalysis law.  

Taking the logarithm of both sides of equation 7.55 produces equation 7.56. 

there should be a linear relationship between the logs of the rate constants and the logs of the values for a general acid-catalyzed reaction involving a series of closely related compounds. Similarly, for general 

The procedure for extracting values of Jtha was described by Stewart (reference 18). 

Acid catalysis of the reaction of water-insoluble hydrocarbons with highly polar acid catalysts depends not only on Hg but also on the extent of stirring. For a discussion, see Busca, G. Chem. Rev. 2007,107,5366. 

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A number of studies of the acid-catalyzed mechanism of enolization have been done. The case of cyclohexanone is illustrative. The reaction is catalyzed by various carboxylic acids and substituted ammonium ions. The effectiveness of these proton donors as catalysts correlates with their pK values. When plotted according to the Bronsted catalysis law (Section 4.8), the value of the slope a is 0.74. When deuterium or tritium is introduced in the a position, there is a marked decrease in the rate of acid-catalyzed enolization h/ d 5. This kinetic isotope effect indicates that the C—H bond cleavage is part of the rate-determining step. The generally accepted mechanism for acid-catalyzed enolization pictures the rate-determining step as deprotonation of the protonated ketone ... 

Catalysis by proton transfer is significant in the snbsnrface and associated environment and is common in homogeneous reactions. The strength of the acid or base is determined by the ionization constant, while its efficiency as a catalyst is controlled by the reaction rate. This relation, known as the Bronsted catalysis law, is expressed as... 

Figure 3.4 Hypothetical free energy vs. reaction coordinate curves for proton transfer from four different acids, AxH, A2H, A3H, A4II, to base B. The Bronsted catalysis law presumes that the effects of structural change on the transition-state free energies will be some constant fraction of their effects on the overall free-energy changes.

The Bronsted catalysis law states that the individual catalytic constants, kn, should be related to the equilibrium acidities by Equation 8.12, or, for a base-catalyzed process, by Equation 8.13. (See Section 3.3, p. 141, for further dis-... 

Equation 8.18 and find relation 8.21 between activation free energy, AG, and standard free energy change, AG°. This equation is equivalent to the Bronsted catalysis law as was shown in Section 3.3 (Equations 3.49 and 3.53), and we may conclude that an interpretation of a as a measure of the position of the transition state is consistent with the Hammond postulate. 

The base-catalysed decomposition of nitramide (3 in Scheme 1.4) is of special historical importance as it was the reaction used to establish the Bronsted catalysis law. The reaction has been studied over manyyears and considerable evidence indicates that the decomposition... 

III. Solvent Isotope Effects in Relation to the Bronsted Catalysis Law. . 277... 

It should be noted that it is, of course, not permissible to use the Bronsted catalysis law to relate rates of proton transfers to rates of deuteron transfers. No such suggestion is implied by the application of equations (68) and (69). 

If a proton-transfer reaction is visualized as a three-body process (Bell, 1959b), a linear free energy relationship is predicted between the acid dissociation constant, Aha, and the catalytic coefficient for the proton-transfer reaction, HA. Figure I shows the relationships between ground-state energies and transition-state energies. This is a particular case of the Bronsted Catalysis Law (Bronsted and Pedersen, 1924) shown in equation (9). The quantities p and q are, respectively, the number of... 

The terms in equation (23) which are independent of the acid concentration show little or no solvent isotope effect. This and considerations following from the Bronsted Catalysis Law make it unlikely that these terms represent cleavage of the complexed substrate by water. A ratedetermining, unimolecular rearrangement from the a- to the v-allylic mercurial was suggested. Oxidative cleavage of some sort is another possibility. 

A similar mechanism is suggested for reaction of the intermediate. The extent of fission of the bond H-A in the transition state has been discussed by a number of authors 2, is, 27 basis of the Bronsted catalysis law. For both steps for... 

The reaction with pinacol is second order (first order with respect to each reactant) in the range pH 0-11 (Price ef a/. , Duke and Bulgrin Buist et al. ). In the same pH range there is no evidence for the formation of an intermediate in appreciable concentration. The dependence of the second-order rate coefficient on pH is complex (Fig. 3) and shows maxima at pH 1 and pH 9.5. In the range pH 2-10 the reaction is general acid-base catalysed (Zuman et al. , Buist et al. ) and for base catalysis the catalytic constants obey the Bronsted catalysis law with a slope of 0.69. Asnotedabove, thekineticsof pinacol oxidation resemble those... 

Spitael J, Kinget R, Naessens K. Dissolution rate of cellulose acetate phthalate and Bronsted catalysis law. Pharm Ind 1980 42 846-849. 

The relationship between the ability of a buffer component to catalyse hydrolysis, denoted by the catalytic coefficient, k, and its dissociation constant, K, may be expressed by the Bronsted catalysis law as... 

To proceed further it is necessary to make some assumption concerning the connection between acidity constant and rate constant of proton (deuteron) transfer (i L,o or dlio)- A connection is suggested by the Bronsted catalysis law (Bronsted and Pedersen, 1924 Bronsted, 1928) ... 

There is ample scope for further investigations of the mechanism of beta-eliminations yielding imines and nitriles. Some of the base-catalysed reactions may be examples of the carbanion mechanism and hydrogen isotope studies and the application of the Bronsted catalysis law to rates of elimination under various reaction conditions could prove informative. 

The rate constants for the dissolution of cellulose acetate phthalate in solutions of different basic salts were determined using an automatic pH-stat method. A linear relationship between the logarithm of the rate constants and the pRg of the basic salts was observed. Evidence was given that the rate of proton transfer, which leads to the dissociation and, consequently, to the dissolution of the polymer, is the rate determining step and is governed by the Bronsted catalysis law."... 

Since such an argument involves several critical assumptions about the shape of the potential-energy curves and the entropy of activation, it is not too surprising that the Bronsted catalysis law has not been found to be completely adequate [21]. This simple argument also predicts that different acids and bases should have rate constants which differ only because their activation energies differ. This prediction is not consistent with available experimental results. 

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