The thermolysis and photolysis of malonic acid in the gas phase

1986 ◽  
Vol 64 (5) ◽  
pp. 967-968 ◽  
Author(s):  
J.-R. Cao ◽  
R. A. Back
Keyword(s):  
Acetic Acid ◽  
Hydrogen Atom ◽  
Transition State ◽  
Gas Phase ◽  
Malonic Acid ◽  
Rate Constants ◽  
Hydrogen Atom Transfer ◽  
Arrhenius Parameters ◽  
First Order ◽  
Order Rate

The thermolysis of malonic acid has been studied briefly in the gas phase at temperatures from 92 to 151 °C at pressures around 0.1 Torr. Major products were CO2 and acetic acid, while smaller amounts (< 5% of the CO2) of CO, acetone, C2H6, and CH4 were formed. Arrhenius parameters of E = 30.9 kcal/mol and log A (s−1) = 13.27 were obtained, based on first-order rate constants for the formation of CO2. It is suggested that the major products are formed by an internal hydrogen-atom transfer through a 4-centre transition state. The gas-phase photolysis was examined briefly using light of 228.8 nm, and gave products very similar to those of the thermolysis.

scholarly journals Absolute rate constants for hydrocarbon autoxidation. 26. Rate constants for reaction of the tert-butylperoxy radical with 1-bromo-2-methylbutane and 1-bromo-3-methylbutane and some related substituted butanes

1979 ◽  
Vol 57 (18) ◽  
pp. 2484-2490 ◽  
Author(s):  
J. A. Howard ◽  
J. H. B. Chenier
Keyword(s):  
Hydrogen Atom ◽  
Transition State ◽  
Kinetic Parameters ◽  
Rate Constants ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Absolute Rate ◽  
Arrhenius Parameters

Rate constants and Arrhenius parameters for reaction of the tert-butylperoxy radical with 1-bromo-2-methylbutane and 1-bromo-3-methylbutane in solution from 30–80 °C have been estimated. The magnitude of these kinetic parameters are consistent with activation of the tertiary hydrogen vicinal to the bromine substituent and the involvement of a "bridged" transition state in the hydrogen atom transfer reaction.Chloro, trimethylsilyl, and trimethylstannyl substituents also activate a vicinal tertiary hydrogen and activation increases in the order trimethylsilyl ∼ trimethylstannyl < chloro < bromo.

The thermal decompositions of carbamates. I. Ethyl N-Methyl-N-phenylcarbamate

1971 ◽  
Vol 24 (12) ◽  
pp. 2541 ◽  
Author(s):  
NJ Daly ◽  
F Ziolkowski
Keyword(s):  
Carbon Dioxide ◽  
Gas Phase ◽  
Rate Constants ◽  
Volume Ratio ◽  
Reaction Vessel ◽  
First Order ◽  
Order Rate

Ethyl N-methyl-N-phenylcarbamate decomposes in the gas phase over the range 329-380� to give N-methylaniline, carbon dioxide, and ethylene. The reaction is quantitative, and is first order in the carbamate. First-order rate constants are described by the equation ������������������� k1 = 1012.44 exp(-45,380/RT) (s-1) and are unaffected by the addition of cyclohexene or by increase in the surface to volume ratio of the reaction vessel. The reaction is considered to be unimolecular and likely to proceed by means of a mechanism of the type represented by the pyrolyses of acetates, xanthates, and carbonates.

Pyrimidine reactions. XI. Amination rates for two chlorodimethylprimidines without solvent

1965 ◽  
Vol 18 (11) ◽  
pp. 1811 ◽  
Author(s):  
DJ Brown ◽  
JM Lyall
Keyword(s):  
Rate Constants ◽  
Second Order ◽  
Arrhenius Parameters ◽  
First Order ◽  
Order Rate

Second-order rate constants, Arrhenius parameters, and isokinetic temperatures are presented for the reactions of 2-chloro-4,6-dimethylpyrimidine and 4-chloro-2,6-dimethylpyrimidine with some n-alkyl-, branched alkyl-, and dialkylamines in the absence of a solvent. The differences between these values and those available for the same reactions in a solvent are briefly discussed. An equation is derived for satisfactorily converting the apparent first-order rate constants previously reported by us into second-order rate constants.

Catalysis by hydrogen halides in the gas phase. XVII. Isobutyric acid and hydrogen bromide

1968 ◽  
Vol 21 (3) ◽  
pp. 725 ◽  
Author(s):  
JTD Cross ◽  
VR Stimson
Keyword(s):  
Carbon Monoxide ◽  
Gas Phase ◽  
Rate Constants ◽  
Hydrogen Bromide ◽  
Isobutyric Acid ◽  
Kcal Mole ◽  
Hydrogen Halides ◽  
Arrhenius Parameters ◽  
First Order ◽  
Added Water

Hydrogen bromide catalyses the decomposition of isobutyric acid into propene, carbon monoxide, and water at 369-454�. Hydrogen bromide is not lost. Individual runs follow the first-order rate law, and the rate constants are proportional to the hydrogen bromide pressure. The Arrhenius parameters are: E = 33.17 kcal mole-1 and A = 1012.87 sec-1 ml mole-1, and the reaction is homogeneous and molecular. Added water or methanol retards the reaction.

The thermal decompositions of carbamates. II. Methyl N-methylcarbamate

1972 ◽  
Vol 25 (7) ◽  
pp. 1453 ◽  
Author(s):  
NJ Daly ◽  
F Ziolkowski
Keyword(s):  
Activation Energy ◽  
Transition State ◽  
Gas Phase ◽  
Rate Constants ◽  
Volume Ratio ◽  
Reaction Vessel ◽  
Phase Reaction ◽  
Methyl Isocyanate ◽  
Gas Phase Reaction ◽  
First Order

Methyl N-methyloarbamate decomposes in the range 370-422� to give methyl isocyanate and methanol. The reaction is first order in carbamate, and the variation of the rate constants with temperature is given by the equation. k = 1012.39 exp(-4806O/RT) (s-l; activation energy in cal mol-l) Rate constants are unaffected by the addition of isobutene or by increase in the surface to volume ratio of the reaction vessel. The addition of alcohols or amines does not reverse the process. The decomposition is considered to be a homogeneous, unimolecular gas-phase reaction, probably proceeding through a four-centred transition state.

Hydrogen Atom Transfer Reaction Free Energy as a Predictor of Abiotic Nitroaromatic Reduction Rate Constants: A Comprehensive Analysis

2019 ◽  
Author(s):  
Dominic Di Toro ◽  
Kevin P. Hickey ◽  
Herbert E. Allen ◽  
Richard F. Carbonaro ◽  
Pei C. Chiu
Keyword(s):  
Free Energy ◽  
Hydrogen Atom ◽  
Hydrogen Atom Transfer ◽  
Energy Model ◽  
Second Order ◽  
Transfer Model ◽  
Atom Transfer ◽  
Order Rate ◽  
Linear Free Energy ◽  
Free Energy Model

<div>A linear free energy model is presented that predicts the second order rate constant for the abiotic reduction of nitroaromatic compounds (NACs). For this situation previously presented models use the one electron reduction potential of the NAC reaction. If such value is not available, it has been has been proposed that it could be computed directly or estimated from the electron affinity (EA). The model proposed herein uses the Gibbs free energy of the hydrogen atom transfer (HAT) as the parameter in the linear free energy model. Both models employ quantum chemical computations for the required thermodynamic parameters. The available and proposed models are compared using second order rate constants obtained from five investigations reported in the literature in which a variety of NACs were exposed to a variety of reductants. A comprehensive analysis utilizing all the NACs and reductants demonstrate that the computed hydrogen atom transfer model and the experimental one electron reduction potential model have similar root mean square errors and residual error probability distributions. In contrast, the model using the computed electron affinity has a more variable residual error distribution with a significant number of outliers. The results suggest that a linear free energy model utilizing computed hydrogen transfer reaction free energy produces a more reliable prediction of the NAC abiotic reduction second order rate constant than previously available methods. The advantages of the proposed hydrogen atom transfer model and its mechanistic implications are discussed as well.</div>

scholarly journals Kinetics and Mechanism of the Change of the 4-Nitrobenzylthio-System into 4,4′-Diformylazoxybenzene in Alkaline Dioxane-Water Media

1985 ◽  
Vol 40 (11) ◽  
pp. 1128-1132
Author(s):  
Y. Riad ◽  
Adel N. Asaad ◽  
G.-A. S. Gohar ◽  
A. A. Abdallah
Keyword(s):  
Acetic Acid ◽  
Sodium Hydroxide ◽  
Rate Constants ◽  
Main Product ◽  
Reaction Medium ◽  
Aqueous Dioxane ◽  
Proton Abstraction ◽  
First Order ◽  
Water Media ◽  
Different Temperatures

Sodium hydroxide reacts with α -(4-nitrobenzylthio)-acetic acid in aqueous-dioxane media to give 4,4'-diformylazoxybenzene as the main product besides 4,4'-dicarboxyazoxybenzene and a nitrone acid. This reaction was kinetically studied in presence of excess of alkali in different dioxane-water media at different temperatures. It started by a fast reversible a-proton abstraction step followed by two consecutive irreversible first-order steps forming two intermediates (α -hydroxy, 4-nitrosobenzylthio)-acetic acid and 4-nitrosobenzaldehyde. The latter underwent a Cannizzaro's reaction, the products of which changed in the reaction medium into 4,4'-diformylazoxybenzene and 4,4'-dicarboxyazoxybenzene. The rate constants and the thermodynamic parameters of the two consecutive steps were calculated and discussed. A mechanism was put forward for the formation of the nitrone acid.Other six 4-nitrobenzyl, aryl sulphides were qualitatively studied and they gave mainly 4,4'-diformylazoxybenzene beside 4,4'-dicarboxyazoxybenzene or its corresponding azo acid.

A kinetic standard for precise calibration of spectrophotometer cell temperature.

1981 ◽  
Vol 27 (5) ◽  
pp. 753-755 ◽  
Author(s):  
P A Adams ◽  
M C Berman
Keyword(s):  
Temperature Dependence ◽  
Rate Constants ◽  
Cell Temperature ◽  
First Order ◽  
Order Rate ◽  
Acid Catalyzed ◽  
Pseudo First Order ◽  
Hydrolysis Of

Abstract We describe a simple, highly reproducible kinetic technique for precisely measuring temperature in spectrophotometric systems having reaction cells that are inaccessible to conventional temperature probes. The method is based on the temperature dependence of pseudo-first-order rate constants for the acid-catalyzed hydrolysis of N-o-tolyl-D-glucosylamine. Temperatures of reaction cuvette contents are measured with a precision of +/- 0.05 degrees C (1 SD).

Sign in / Sign up

Export Citation Format

Share Document