The mechanism of the thermal decarbonylation of 2,2-dimethyl-3-butenal

1977 ◽  
Vol 55 (22) ◽  
pp. 3951-3954 ◽  
Author(s):  
Robert J. Crawford ◽  
Stuart Lutener ◽  
Hirokazu Tokunaga
Keyword(s):  
Carbon Monoxide ◽  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
First Order ◽  
First Order Kinetics ◽  
Kinetic Isotope ◽  
Hydrogen Deuterium ◽  
Thermal Decarbonylation

The thermal decarbonylation of 2,2-dimethyl-3-butenal is shown to be an intramolecular extrusion of carbon monoxide concerted with the transfer of hydrogen (deuterium) to the γ-position. The reaction displays a kinetic isotope effect of 2.8 (at 296.9 °C) and follows first order kinetics (Ea = 44.2 ± 0.2 kcal mol−1, log A = 13.4 ± 0.3).

ORTHO PARTICIPATION IN THE CONVERSION OF syn-BENZALDOXIME ESTERS TO NITRILES

1965 ◽  
Vol 43 (12) ◽  
pp. 3178-3187 ◽  
Author(s):  
Robert J. Crawford ◽  
Charles Woo
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Alcoholic Solution ◽  
First Order ◽  
Rate Determining Step ◽  
First Order Kinetics ◽  
Kinetic Isotope ◽  
Marked Enhancement

Substituted syn-benzaldoxime esters are transformed, in an alcoholic solution, to the corresponding nitriles according to first-order kinetics. All ortho substituents were observed to accelerate the rate of nitrile formation relative to the corresponding para derivative. While the ko/kp ratios for the bromo, chloro, fluoro, methoxy, and methyl substituents fall within the range of 2 to 9, the iodo and methylthio substituents are 119 and 11 000 respectively. Isotopic replacement of the aldoximino hydrogen by deuterium gives rise to a kinetic isotope effect, kH/kD being 5.21 for syn-o-chlorobenzaldoxime p-toluenesulfonate, 1.22 for syn-o-iodobenzaldoxime p-toluenesulfonate, and 1.23 for syn-o-methylthiobenzaldoxime o-iodobenzoate. The marked enhancement of rate and the absence of an appreciable isotope effect are considered to be associated with sulfur and iodine participation in the rate-determining step. A mechanism which is capable of explaining the results observed is suggested.

ChemInform Abstract: HYDROGEN/DEUTERIUM KINETIC ISOTOPE EFFECT IN THE METHANATION OF CARBON MONOXIDE ON A NICKEL-SILICA CATALYST

1983 ◽  
Vol 14 (43) ◽  
Author(s):  
P. F. M. T. VAN NISSELROOIJ ◽  
J. A. M. LUTTIKHOLT ◽  
R. Z. C. VAN MEERTEN ◽  
M. H. J. M. DE CROON ◽  
J. W. E. COENEN
Keyword(s):  
Carbon Monoxide ◽  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Kinetic Isotope ◽  
Hydrogen Deuterium

Hydrogen/deuterium kinetic isotope effect in the methanation of carbon monoxide on a nickel-silica catalyst

1983 ◽  
Vol 6 (3) ◽  
pp. 271-281 ◽  
Author(s):  
P.F.M.T. van Nisselrooij ◽  
J.A.M. Luttikholt ◽  
R.Z.C. van Meerten ◽  
M.H.J.M. de Croon ◽  
J.W.E. Coenen
Keyword(s):  
Carbon Monoxide ◽  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Kinetic Isotope ◽  
Hydrogen Deuterium

Primary kinetic isotope effect in the gas phase photochlorination of ethyl chloride-1-d1

1984 ◽  
Vol 62 (5) ◽  
pp. 899-906 ◽  
Author(s):  
Jan Niedzielski ◽  
T. Yano ◽  
E. Tschuikow-Roux
Keyword(s):  
Activation Energy ◽  
Gas Phase ◽  
Isotope Effect ◽  
Ground State ◽  
Rate Constants ◽  
Kinetic Isotope Effect ◽  
Kinetic Isotope ◽  
Primary Reference ◽  
Hydrogen Deuterium ◽  
Increasing Temperature

The abstraction of hydrogen/deuterium from CH3CHDCl by ground state chlorine atoms produced photolytically from Cl2 has been investigated at temperatures betwen 280 and 368 K. The relative rates for the internal competition[Formula: see text]are found to conform to an Arrhenius rate law:[Formula: see text]These data, taken together with the external competition results for the C2H5Cl/CH3CHDCl system, in conjunction with the competitive results using CH4 as a primary reference, have yielded the rate constants (cm3 s−1):[Formula: see text]The relatively weak primary kinetic isotope effect, kH/kD, decreases with increasing temperature from 1,855 at 280 K to 1.66 at 365 K. The results are compared with those obtained based on the BEBO method. While both the trend and the magnitude of the kinetic isotope effect are satisfactorily predicted, the activation energy is not.

scholarly journals Kinetics and Mechanism of the Decarboxylation of Pyrrole-2-carboxylic Acid in Aqueous Solution

1971 ◽  
Vol 49 (7) ◽  
pp. 1032-1035 ◽  
Author(s):  
G. E. Dunn ◽  
Gordon K. J . Lee
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Carboxylic Acid ◽  
Isotope Effect ◽  
Anthranilic Acid ◽  
Kinetic Isotope Effect ◽  
Pyrrole Ring ◽  
First Order ◽  
Kinetic Isotope ◽  
Ph Range

The decarboxylation of pyrrole-2-carboxylic acid in aqueous buffers at 50° and ionic strength 1.0 has been found to be first order with respect to substrate at a fixed pH. As the pH is decreased, the rate constant increases slightly in the pH range 3–1, then rises rapidly from pH 1 to 10 M HCl. The 13C-carboxyl kinetic isotope effect is 2.8% in 4 M HClO4 and negligible at pH ~ 3. These observations can be accounted for by a mechanism, previously proposed for the decarboxylation of anthranilic acid, in which the species undergoing decarboxylation is the carboxylate ion protonated at the 2-position of the pyrrole ring. This intermediate can be formed both by ring-protonation of the carboxylate anion and by ionization of the ring-protonated acid. At low acidities ring-protonation is rate determining, but at higher acidities the rate of protonation exceeds that of decarboxylation.

scholarly journals Path Integral Calculation of the Hydrogen/Deuterium Kinetic Isotope Effect in Monoamine Oxidase A-Catalyzed Decomposition of Benzylamine

Molecules ◽  
2019 ◽  
Vol 24 (23) ◽  
pp. 4359 ◽  
Author(s):  
Mateusz Z. Brela ◽  
Alja Prah ◽  
Marek Boczar ◽  
Jernej Stare ◽  
Janez Mavri
Keyword(s):  
Monoamine Oxidase ◽  
Isotope Effect ◽  
Path Integral ◽  
Kinetic Isotope Effect ◽  
Monoamine Oxidase A ◽  
Kinetic Isotope ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Hydrogen Deuterium ◽  
Rate Limiting

Monoamine oxidase A (MAO A) is a well-known enzyme responsible for the oxidative deamination of several important monoaminergic neurotransmitters. The rate-limiting step of amine decomposition is hydride anion transfer from the substrate α–CH2 group to the N5 atom of the flavin cofactor moiety. In this work, we focus on MAO A-catalyzed benzylamine decomposition in order to elucidate nuclear quantum effects through the calculation of the hydrogen/deuterium (H/D) kinetic isotope effect. The rate-limiting step of the reaction was simulated using a multiscale approach at the empirical valence bond (EVB) level. We applied path integral quantization using the quantum classical path method (QCP) for the substrate benzylamine as well as the MAO cofactor flavin adenine dinucleotide. The calculated H/D kinetic isotope effect of 6.5 ± 1.4 is in reasonable agreement with the available experimental values.

Sign in / Sign up

Export Citation Format

Share Document