Kinetics of Base-Catalysed Hydrolysis and Cyclisation of Substituted Acetamide and Benzamide O-(Phenoxycarbonyl)oximes

1999 ◽  
Vol 64 (10) ◽  
pp. 1641-1653 ◽  
Author(s):  
Jaromír Mindl ◽  
Jaromír Kaválek ◽  
Helena Straková ◽  
Vojeslav Štěrba
Keyword(s):  
Reaction Mechanism ◽  
Ph Dependence ◽  
Bond Formation ◽  
Reaction Step ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Substituted Benzamide ◽  
Ph Range ◽  
Rate Limiting ◽  
Kinetics Of

The reaction kinetics of acetamide O-(4-nitrophenoxycarbonyl)oxime have been studied in aqueous buffers at pH 2-11. At pH > 9, the pH dependence of kobs is linear with slope 1, the cyclisation to 3-methyl-1,2,4-oxadiazol-5(4H)-one and 4-nitrophenol being the only reaction. At pH < 7.5, the only reaction is the hydrolysis giving 4-nitrophenol and acetamidoxime. The dependence of kobs on pH has been used to determine the rate equation and to propose the reaction mechanism. The cyclisation kinetics of substituted benzamide O-(phenoxycarbonyl)oximes have been studied in the pH range from 9.25 to 11. The reaction mechanism has been proposed based on the ρ constants found. In the first reaction step, the proton is split off from the NH2 group; the subsequent, rate-limiting step involves simultaneous N-C bond formation and C-O bond splitting.

scholarly journals A study of the oxidation of butan-1-ol and propan-2-ol by nicotinamide-adenine dinucleotide catalysed by yeast alcohol dehydrogenase.

1975 ◽  
Vol 147 (3) ◽  
pp. 541-547 ◽  
Author(s):  
C J Dickenson ◽  
F M Dickinson
Keyword(s):  
Alcohol Dehydrogenase ◽  
Ternary Complexes ◽  
Kinetics Of Oxidation ◽  
Yeast Alcohol Dehydrogenase ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Ph Range ◽  
Rate Limiting ◽  
Kinetics Of ◽  
Flow Experiments

1. The kinetics of oxidation of butan-1-ol and propan-2-ol by NAD+, catalysed by yeast alcohol dehydrogenase, were studied at 25 degrees C from pH 5.5 to 10, and at pH 7.05 from 14 degrees to 44 degrees C, 2. Under all conditions studied the results are consistent with a mechanism whereby some dissociation of coenzyme from the active enzyme-NAD+-alcohol ternary complexes occurs, and the mechanism is therefore not strictly compulsory order. 3. A primary 2H isotopic effect on the maximum rates of oxidation of [1-2H2]butan-1-ol and [2H7]propan-2-ol was found at 25 degrees C over the pH range 5.5-10. Further, in stopped-flow experiments at pH 7.05 and 25 degrees C, there was no transient formation of NADH in the oxidation of butan-1-ol and propan-2-ol. The principal rate-limiting step in the oxidation of dependence on pH of the maximum rates of oxidation of butan-1-ol and propan-2-ol is consisten with the possibility that histidine and cysteine residues may affect or control catalysis.

Kinetics of cyclization of S-ethoxycarbonylmethylisothiouronium chloride to 2-imino-4-thiazolidone

1979 ◽  
Vol 44 (3) ◽  
pp. 912-917 ◽  
Author(s):  
Vladimír Macháček ◽  
Said A. El-bahai ◽  
Vojeslav Štěrba
Keyword(s):  
Hydrochloric Acid ◽  
Dilute Hydrochloric Acid ◽  
Base Catalysis ◽  
General Base ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Kinetics Of Formation ◽  
Acid Catalyzed ◽  
Rate Limiting ◽  
Kinetics Of

Kinetics of formation of 2-imino-4-thiazolidone from S-ethoxycarbonylmethylisothiouronium chloride has been studied in aqueous buffers and dilute hydrochloric acid. The reaction is subject to general base catalysis, the β value being 0.65. Its rate limiting step consists in acid-catalyzed splitting off of ethoxide ion from dipolar tetrahedral intermediate. At pH < 2 formation of this intermediate becomes rate-limiting; rate constant of its formation is 2 . 104 s-1.

Kinetics and mechanism of cyclization of N-(2-methoxycarbonylphenyl)-N’-methylsulphonamide to 3-methyl-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide

1991 ◽  
Vol 56 (8) ◽  
pp. 1701-1710 ◽  
Author(s):  
Jaromír Kaválek ◽  
Vladimír Macháček ◽  
Miloš Sedlák ◽  
Vojeslav Štěrba
Keyword(s):  
Potassium Hydroxide ◽  
Acid Catalysis ◽  
Potassium Hydroxide Solution ◽  
Hydroxide Solution ◽  
General Base ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Cyclization Kinetics ◽  
Rate Limiting ◽  
Kinetics Of

The cyclization kinetics of N-(2-methylcarbonylphenyl)-N’-methylsulfonamide (IIb) into 3-methyl-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide (Ib) has been studied in ethanolamine, morpholine, and butylamine buffers and in potassium hydroxide solution. The cyclization is subject to general base and general acid catalysis. The value of the Bronsted coefficient β is about 0.1, which indicates that splitting off of the proton from negatively charged tetrahedral intermediate represents the rate-limiting and thermodynamically favourable step. In the solutions of potassium hydroxide the cyclization of dianion of the starting ester IIb probably becomes the rate-limiting step.

scholarly journals Understanding the reaction mechanism of Kolbe electrolysis on Pt anodes

2021 ◽  
Author(s):  
Sihang Liu ◽  
Nitish Govindarajan ◽  
Hector Prats ◽  
Karen Chan
Keyword(s):  
Reaction Mechanism ◽  
Potential Range ◽  
Microkinetic Model ◽  
Rate Determining Step ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Tafel Slopes ◽  
Kolbe Electrolysis ◽  
Kolbe Reaction ◽  
Rate Limiting

Kolbe electrolysis has been proposed an efficient electrooxidation process to synthesize (un)symmetrical dimers from biomass-based carboxylic acids. However, the reaction mechanism of Kolbe electrolysis remains controversial. In this work, we develop a DFT- based microkinetic model to study the reaction mechanism of Kolbe electrolysis of acetic acid (CH3COOH) on both pristine and partially oxidized Pt anodes. We show that the shift in the rate-determining step of oxygen evolution reaction (OER) on Pt(111)@α-PtO2 surface from OH* formation to H2O adsorption gives rise to the large Tafel slopes, i.e., the inflection zones, observed at high anodic potentials in experiments on Pt anodes. The activity passivation as a result of the inflection zone is further exacerbated in the presence of Kolbe species (i.e., CH3COO* and CH3*). Our simulations find the CH3COO* decarboxylation and CH3* dimerization steps determine the activity of Kolbe reaction during inflection zone. In contrast to the Pt(111)@α-PtO2 surface, Pt(111) shows no activity towards Kolbe products as the CH3COO* decarboxylation step is limiting throughout the considered potential range. This work resolves major controversies in the mechanistic analyses of Kolbe electrolysis on Pt anodes: the origin of the inflection zone, and the identity of the rate limiting step.

scholarly journals Kinetic modelling of hydrogen transfer deoxygenation of a prototypical fatty acid over a bimetallic Pd60Cu40 catalyst: an investigation of the surface reaction mechanism and rate limiting step

2020 ◽  
Vol 5 (9) ◽  
pp. 1682-1693
Author(s):  
Kin Wai Cheah ◽  
Suzana Yusup ◽  
Martin J. Taylor ◽  
Bing Shen How ◽  
Amin Osatiashtiani ◽  
...  
Keyword(s):  
Oleic Acid ◽  
Reaction Mechanism ◽  
Hydrogen Transfer ◽  
Surface Reaction ◽  
Kinetic Modelling ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Cu Catalyst ◽  
P Application ◽  
Rate Limiting

Application of tetralin as a source of hydrogen for catalytic conversion of oleic acid to diesel-like hydrocarbons using a bimetallic Pd–Cu catalyst.

scholarly journals Unveiling the Rate-Limiting Step of the Bc1 Complex Reaction Mechanism

2019 ◽  
Vol 116 (3) ◽  
pp. 419a
Author(s):  
Angela M. Barragan ◽  
Alexander V. Soudackov ◽  
Zaida Luthey-Schulten ◽  
Klaus Schulten ◽  
Sharon Hammes-Schiffer ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Complex Reaction ◽  
Bc1 Complex ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

Oxidation of 1- and 2-acetylnaphthalenes by iodate - a kinetic study

1990 ◽  
Vol 55 (6) ◽  
pp. 1535-1540 ◽  
Author(s):  
Prerepa Manikyamba
Keyword(s):  
Solvent Effect ◽  
Enol Form ◽  
Aqueous Methanol ◽  
Kinetics Of Oxidation ◽  
First Order ◽  
Carbonium Ion ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting ◽  
Kinetics Of

Kinetics of oxidation of 1- and 2-acetylnaphthalenes by iodate in the presence of sulphuric acid in aqueous methanol has been studied. The reaction is first order with respect to both [iodate] and [acetylnaphthalene]. Solvent effect indicates a cation-dipole type of interaction in the rate limiting step. A mechanism is proposed with a slow attack of IO2+ on enol form of acetylnaphthalene forming an intermediate carbonium ion, which ultimately gives corresponding ω-hydroxyacetylnaphthalene. The higher reactivity of 2-acetyl isomer is attributed to the greater stability of the corresponding carbonium ion than that of 1-acetyl isomer.

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