scholarly journals The neutral hydrolysis of methyl acetate — Part 2. Is there a tetrahedral intermediate?

2009 ◽  
Vol 87 (4) ◽  
pp. 544-555 ◽  
Author(s):  
Zheng Shi ◽  
Yih-huang Hsieh ◽  
Noham Weinberg ◽  
Saul Wolfe
Keyword(s):  
Acetic Acid ◽  
Methyl Acetate ◽  
Acid Catalysis ◽  
Experimental Result ◽  
Acid Product ◽  
General Acid ◽  
One Step ◽  
Hydrolysis Of ◽  
Step Mechanism ◽  
Tetrahedral Intermediates

A computational strategy that reproduces the experimental rates of hydration of formaldehyde, acetaldehyde, acetone, and cyclohexanone and the rates of acetic acid and 2-hydroxypyridine-catalyzed hydration of acetone has been extended to the results of the neutral hydrolysis of methyl acetate reported in Part 1. Calculations have been performed for one-step and two-step mechanisms, with cooperative assistance from one to three additional water molecules in the presence and absence of the acetic acid product. The calculations predict that, for the neutral reaction, a one-step mechanism will be favoured if tetrahedral intermediates have a short lifetime and do not interconvert prior to breakdown (case A), and a two-step mechanism will be operative if tetrahedral intermediates are allowed to interconvert prior to breakdown (case B). The experimental results are consistent with the predictions of case A. In the presence of acetic acid, case A predicts that the acid will contribute only 1.6% to the overall rate, a negligible acceleration over the noncatalytic process, and case B predicts general acid catalysis to be an order of magnitude greater than the experimental result. It is concluded that the neutral hydrolysis of methyl acetate is mainly a cooperative one-step process, and that general acid catalysis by the acetic acid product does not occur.

The neutral hydrolysis of methyl acetate — Part 1. Kinetic experiments

2009 ◽  
Vol 87 (4) ◽  
pp. 539-543 ◽  
Author(s):  
Yih-Huang Hsieh ◽  
Noham Weinberg ◽  
Saul Wolfe
Keyword(s):  
Acetic Acid ◽  
Hydrochloric Acid ◽  
Rate Constant ◽  
Rate Constants ◽  
Methyl Acetate ◽  
Acid Catalysis ◽  
Acid Product ◽  
Neutral Reaction ◽  
Uncatalyzed Reaction ◽  
Hydrolysis Of

The neutral hydrolysis of methyl acetate and catalysis of the reaction by the acetic acid product have been studied in the temperature range 90–110 °C. Extrapolated to 25 °C, the rate constants are 0.17 × 10−8 s–1 for the uncatalyzed reaction and 1.4 × 10−4 (mol/L)–1s–1 for the catalyzed reaction. The acid catalysis is specific not general: at 90 °C the rate constants for hydrochloric acid catalysis and catalysis by ionized acetic acid are the same as the rate constant, kH = 1.4 × 10−2 (mol/L)–1s–1, determined in the neutral reaction.

Hydrolysis of thioimidate esters. Tetrahedral intermediates and general acid catalysis

1967 ◽  
Vol 89 (26) ◽  
pp. 6984-6993 ◽  
Author(s):  
Rama K. Chaturvedi ◽  
Andrew E. MacMahon ◽  
Gaston L. Schmir
Keyword(s):  
Acid Catalysis ◽  
General Acid ◽  
Hydrolysis Of ◽  
Tetrahedral Intermediates

Efficient intramolecular general acid catalysis of the hydrolysis of a dialkyl acetal

1996 ◽  
pp. 2355 ◽  
Author(s):  
Christopher J. Brown ◽  
Anthony J. Kirby
Keyword(s):  
Acid Catalysis ◽  
General Acid ◽  
Hydrolysis Of

General acid catalysis of ketal hydrolysis. The hydrolysis of tropone diethyl ketal

1969 ◽  
Vol 91 (25) ◽  
pp. 7163-7166 ◽  
Author(s):  
Edwin Anderson ◽  
Thomas H. Fife
Keyword(s):  
Acid Catalysis ◽  
General Acid ◽  
Hydrolysis Of

General acid catalysis in the hydrolysis of benzo[a]pyrene 7,8-diol 9,10-epoxides

1979 ◽  
Vol 101 (17) ◽  
pp. 5086-5088 ◽  
Author(s):  
Dale L. Whalen ◽  
Angela M. Ross ◽  
Jean A. Montemarano ◽  
Dhiren R. Thakker ◽  
Harukiko Yagi ◽  
...  
Keyword(s):  
Acid Catalysis ◽  
General Acid ◽  
Hydrolysis Of

Kinetics of the hydrolysis of the dichromate ion. V. General acid catalysis

1969 ◽  
Vol 73 (12) ◽  
pp. 4391-4394 ◽  
Author(s):  
R. Baharad ◽  
Berta Perlmutter-Hayman ◽  
Michael A. Wolff
Keyword(s):  
Acid Catalysis ◽  
General Acid ◽  
Kinetics Of ◽  
Hydrolysis Of

General acid catalysis and the pH-independent hydrolysis of 2-(p-nitrophenoxy) tetrahydropyran

1970 ◽  
Vol 92 (6) ◽  
pp. 1681-1684 ◽  
Author(s):  
Thomas H. Fife ◽  
Lily H. Brod
Keyword(s):  
Acid Catalysis ◽  
General Acid ◽  
Hydrolysis Of

scholarly journals pH-dependence and structure–activity relationships in the papain-catalysed hydrolysis of anilides

1971 ◽  
Vol 124 (1) ◽  
pp. 117-122 ◽  
Author(s):  
G. Lowe ◽  
Y. Yuthavong
Keyword(s):  
Acid Catalysis ◽  
Ph Dependence ◽  
Base Catalysis ◽  
General Base ◽  
Structure Activity ◽  
Equilibrium Binding ◽  
General Acid ◽  
Leaving Group ◽  
Hydrolysis Of ◽  
Equilibrium Binding Constant

The pH-dependence of the Michaelis–Menten parameters for the papain-catalysed hydrolysis of N-acetyl-l-phenylalanylglycine p-nitroanilide was determined. The equilibrium binding constant, Ks, is independent of pH between 3.7 and 9.3, whereas the acylation constant, k+2, shows bell-shaped pH-dependence with apparent pKa values of 4.2 and 8.2. The effect of substituents in the leaving group on the acylation constant of the papain-catalysed hydrolysis of hippuryl anilides and N-acetyl-l-phenylalanylglycine anilides gives rise in both series to a Hammett ρ value of -1.04. This indicates that the enzyme provides electrophilic, probably general-acid, catalysis, as well as the nucleophilic or general-base catalysis previously found. A mechanism involving a tetrahedral intermediate whose formation is general-base-catalysed and whose breakdown is general-acid-catalysed seems most likely. The similarity of the Hammett ρ values appears to exclude facilitated proton transfer as a means through which the specificity of papain is expressed.

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