Reactivity of proton and general acid with 1,3-bis-(4-methylphenyl)triazene in aqueous methanol

1990 ◽  
Vol 55 (11) ◽  
pp. 2701-2706 ◽  
Author(s):  
Oldřich Pytela ◽  
Taťjana Nevěčná ◽  
Jaromír Kaválek
Keyword(s):  
Benzoic Acid ◽  
Transition State ◽  
Rate Constant ◽  
Acid Catalysis ◽  
Methanol Concentration ◽  
Binary Solvent ◽  
Aqueous Methanol ◽  
Solvent Water ◽  
General Acid ◽  
Activated Complex

The effect of concentration of benzoic acid and composition of the binary solvent water-methanol on the rate of decomposition of 1,3-bis(4-methylphenyl)triazene has been studied. It has been found that both general acid catalysis by undissociated benzoic acid and catalysis by the proton are significant. The rate constant kHA of general acid catalysis decreases monotonously with decreasing amount of water in the mixture due to preferred solvation of the activated complex as compared with the educts. The rate constant kH of the catalysis by proton in its dependence on methanol concentration exhibits a minimum for 80% (by wt.) of methanol in the mixture. This phenomenon is caused by formation of the conjugated acid from more basic methanol and proton with simultaneous solvation by water and methanol; the particle thus formed is a weaker acid as compared with the complexes existing in water or in methanol. The kH value is higher in methanol than in water due to preferred solvation of the educts as compared with that of the transition state.

Static Solvent Effects, Transition-State Theory

2018 ◽  
Author(s):  
Niels Engholm Henriksen ◽  
Flemming Yssing Hansen
Keyword(s):  
Transition State ◽  
Rate Constant ◽  
Solvent Effects ◽  
Transition State Theory ◽  
Equilibrium Structure ◽  
State Theory ◽  
Potential Of Mean Force ◽  
Distribution Functions ◽  
Average Force ◽  
Activated Complex

This chapter discusses static solvent effects on the rate constant for chemical reactions in solution. It starts with a brief discussion of the thermodynamic formulation of transition-state theory. The static equilibrium structure of the solvent will modify the potential energy surface for the chemical reaction. This effect is analyzed within the framework of transition-state theory. The rate constant is expressed in terms of the potential of mean force at the activated complex. Various definitions of this potential and their relations to n-particle- and pair-distribution functions are considered. The potential of mean force may, for example, be defined such that the gradient of the potential gives the average force on an atom in the activated complex, Boltzmann averaged over all configurations of the solvent. It concludes with a discussion of a relation between the rate constants in the gas phase and in solution.

Solubility and dielectric properties of benzoic acid in a binary solvent: Water-ethylene glycol

2003 ◽  
Vol 108 (1-3) ◽  
pp. 119-133 ◽  
Author(s):  
A. Yurquina ◽  
M.E. Manzur ◽  
P. Brito ◽  
R. Manzo ◽  
M.A.A. Molina
Keyword(s):  
Dielectric Properties ◽  
Ethylene Glycol ◽  
Benzoic Acid ◽  
Binary Solvent ◽  
Solvent Water

General acid catalysis in benzoic acid-Crystal Violet carbinol base reactions in toluene

2012 ◽  
Vol 44 (8) ◽  
pp. 570-576 ◽  
Author(s):  
Susanta K. Sen Gupta ◽  
Sangeeta Mishra ◽  
V. Radha Rani ◽  
Udai Arvind
Keyword(s):  
Benzoic Acid ◽  
Crystal Violet ◽  
Acid Catalysis ◽  
Acid Crystal ◽  
General Acid

Intramolecular general acid catalysis of sulfate transfer — Nucleophilic attack by oxyanions on the SO3– group

2005 ◽  
Vol 83 (9) ◽  
pp. 1629-1636 ◽  
Author(s):  
Anthony J Kirby ◽  
José Carlos Gesser ◽  
Florian Hollfelder ◽  
Jacks P Priebe ◽  
Faruk Nome
Keyword(s):  
Hydrogen Bond ◽  
Transition State ◽  
Acid Catalysis ◽  
Nucleophilic Attack ◽  
General Acid ◽  
State Transfer ◽  
Carboxylate Anions ◽  
Mechanism Of Hydrolysis ◽  
Intramolecular Hydrogen ◽  
Hydrolysis Of

The mechanism of hydrolysis of 8-N,N-dimethylaminonaphthyl sulfate closely resembles that of the corresponding phosphate monoester. Nucleophilic attack by water on the sulfate group of the zwitterion is catalyzed by the neighbouring dimethylammonium group, acting as a particularly efficient general acid through the intramolecular hydrogen bond. This hydrogen bond is present in both reactant and product, but is strongest in the transition state. Transfer of the sulfuryl group to oxygen nucleophiles, including water and carboxylate anions, shows steric and electrostatic effects, and a sensitivity to basicity which is low, but significantly higher than expected for uncatalyzed transfer of the SO3– group.Key words: sulfate, sulfatase, intramolecular, general acid catalysis, promiscuity.

Hydrolysis of 4-Nitro-2-(trifluoroacetylamino)benzoic acid: Buffer catalysis, micellar catalysis and intramolecular general acid catalysis

1984 ◽  
Vol 37 (5) ◽  
pp. 977
Author(s):  
TJ Broxton
Keyword(s):  
Benzoic Acid ◽  
Acid Catalysis ◽  
Acidic Solution ◽  
Micellar Catalysis ◽  
Bond Breaking ◽  
Solution Rate ◽  
Solution Ph ◽  
General Acid ◽  
Ph Range ◽  
Hydrolysis Of

The hydrolysis of 4-nitro-2-(trifluoroacetylamino)benzoic acid was studied over the pH range 0-13. In strongly acidic solution (pH 0-3), intramolecular general acid catalysis was observed. In alkaline solution, rate determining protonation of the nitrogen atom of the intermediate complex formed by attack of hydroxide ion on the substrate, was observed. The alkaline hydrolysis was subject to significant micellar catalysis and this was accompanied by a change of mechanism to solvent assisted C-N bond breaking. At intermediate pH (4-8), the reaction was subject to significant buffer catalysis, and deprotonation of the intermediate formed by the attack of water on the substrate was proposed.

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