The kinetics of the photo-oxidation of benzaldehyde

1953 ◽  
Vol 218 (1133) ◽  
pp. 175-189 ◽  
Keyword(s):  
Rate Constants ◽  
Peroxy Radical ◽  
Photochemical Oxidation ◽  
Square Root ◽  
Peroxy Radicals ◽  
Photo Oxidation ◽  
Rate Determining Step ◽  
Perbenzoic Acid ◽  
Kinetics Of ◽  
Overall Kinetics

The direct photochemical oxidation of liquid benzaldehyde in n -decane solution has been investigated at temperatures from 5 to 20° C, the primary product being perbenzoic acid. The overall kinetics of the reaction are simple, the rate being proportional to the first power of the concentration of the aldehyde and to the square root of the intensity of the absorbed light. The rate is independent of oxygen pressure. These kinetics indicate that the dehydrogenation of the aldehyde by the peroxy radical is the rate-determining step in propagation. The termination step involves the interaction of two peroxy radicals. By means of the retardation and sector techniques the rate of initiation of the oxidation and the values of the rate constants have been determined.

The kinetics of the oxidation of mixtures of benzaldehyde and n -decanal

1953 ◽  
Vol 218 (1133) ◽  
pp. 163-175 ◽  
Keyword(s):  
Co Oxidation ◽  
Rate Constants ◽  
Peroxy Radical ◽  
Peroxy Radicals ◽  
Absolute Rate ◽  
Kinetic Chain ◽  
Reaction Coefficient ◽  
The Individual ◽  
Kinetics Of ◽  
Oxidation System

The photo-induced co-oxidation of liquid benzaldehyde and decanal mixtures has been investigated as representative of a co-oxidation system of two components. The kinetics of the reaction clearly show that these aldehydes do not separately oxidize; instead, both molecules are involved in a single kinetic chain. The system is analogous to that encountered in copolymerization. By analysis of the aldehyde ratio during oxidation the relative reactivity of the two aldehydes to a given peroxy radical may be determined. Utilizing the rate constants for the oxidation of the individual aldehydes, the absolute rate constants for the four propagation steps in the co-oxidation system can be calculated. By making use of the retarder technique the rate of initiation of oxidation has been determined as a function of aldehyde composition. The measurement of the overall rate of oxidation makes it possible to determine the cross-reaction coefficient for the interaction of the peroxy radicals. A so-called Φ value for this coefficient is 4.

Absolute rate constants for hydrocarbon autoxidation. VI. Alkyl aromatic and olefinic hydrocarbons

1967 ◽  
Vol 45 (8) ◽  
pp. 793-802 ◽  
Author(s):  
J. A. Howard ◽  
K. U. Ingold
Keyword(s):  
Hydrogen Atom ◽  
Steric Hindrance ◽  
Rate Constants ◽  
Peroxy Radical ◽  
Electron System ◽  
Chain Termination ◽  
The Self ◽  
Hydrogen Atom Abstraction ◽  
Peroxy Radicals ◽  
Absolute Rate

Absolute rate constants have been measured for the autoxidation of a large number of hydrocarbons at 30 °C. The chain-propagating and chain-terminating rate constants depend on the structure of the hydrocarbon and also on the structure of the chain-carrying peroxy radical. With certain notable exceptions which are mainly due to steric hindrance, the rate constants for hydrogen-atom abstraction increase in the order primary < secondary < tertiary; and, for compounds losing a secondary hydrogen atom, the rate constants increase in the order unactivated < acyclic activated by a single π-electron system < cyclic activated by a single Π-system < acyclic activated by two π-systems < cyclic activated by two π-systems. The rate constants for chain termination by the self-reaction of two peroxy radicals generally increase in the order tertiary peroxy radicals < acyclic allylic secondary  [Formula: see text] cyclic secondary  [Formula: see text] acyclic benzylic secondary < primary peroxy radicals < hydroperoxy radicals.

The retroaldol reaction of 3-methyl-2-butenal

1983 ◽  
Vol 61 (1) ◽  
pp. 171-178 ◽  
Author(s):  
J. Peter Guthrie ◽  
Brian A. Dawson
Keyword(s):  
Sodium Hydroxide ◽  
Equilibrium Constant ◽  
Rate Constants ◽  
Equilibrium Constants ◽  
Aqueous Sodium Hydroxide ◽  
Initial Increase ◽  
Aqueous Sodium ◽  
Rate Determining Step ◽  
Kinetics Of

In aqueous sodium hydroxide solutions at 25 °C, 3-methyl-2-butenal, 1c, undergoes retroaldol cleavage to acetone and acetaldehyde. The kinetics of the retroaldol reaction were followed spectrophotometrically at 242 nm and showed simple first order behavior. When 3-methyl-3-hydroxybutanal, 2c, was added to aqueous sodium hydroxide solutions at 25 °C, there was an initial increase in absorbance at 242 nm, attributed to formation of 1c, followed by a 20-fold slower decrease; the rate of the slow decrease matches the rate of disappearance of 1c under the same conditions. Analysis of the kinetics allows determination of the three rate constants needed to describe the system: khyd = 0.00342; kdehyd = 0.00832; kretro = 0.0564; all M−1 s−1. The equilibrium constant for enone hydration is 0.41. Rate constants for the analogous reactions for acrolein and crotonaldehyde could be obtained from the literature. There is a reasonable rate–equilibrium correlation for the retroaldol step. For the enone hydration step, rate and equilibrium constants respond differently to replacement of hydrogen by methyl. It is proposed that this results from release of strain after the rate-determining step by rotation about a single bond; this decrease in strain is reflected in the equilibrium constant but not in the rate constant.

Mechanism of bromination of a quaternary pyrimidinium cation. Change of rate determining step with acidity

1978 ◽  
Vol 56 (23) ◽  
pp. 2970-2976 ◽  
Author(s):  
Oswald S. Tee ◽  
David C. Thackray ◽  
Charles G. Berks
Keyword(s):  
Kinetic Study ◽  
Rate Constants ◽  
Aqueous Media ◽  
Stopped Flow ◽  
Flow Method ◽  
High Acidity ◽  
Rate Determining Step ◽  
Kinetics Of ◽  
Good Agreement

The kinetics of bromination of the 1,2-dihydro-1,3-dimethyl-2-oxopyrimidinium cation (Q+) in aqueous media (pH 0–5) have been studied using the stopped-flow method. At the higher acidities (pH < 2) the results are consistent with rate determining attack by bromine upon the pseudobase (QOH), whereas at low acidities (pH > 4) it appears that pseudobase formation is rate determining. The change occurs because at high acidity the reversal of the pseudobase QOH to the cation is fast relative to bromine attack, whereas at low acidity the converse is true. Results obtained at intermediate acidities (pH 2–4) are consistent with this interpretation.A separate kinetic study of pseudobase formation (and decomposition) yielded rate constants in good agreement with those derived from the bromination study.

Alkoxyphosphonium ions. 5. Kinetics of the Michaelis–Arbuzov intermediate

1986 ◽  
Vol 64 (6) ◽  
pp. 1156-1160 ◽  
Author(s):  
Edward S. Lewis ◽  
Bridget A. McCortney
Keyword(s):  
Propylene Carbonate ◽  
Methyl Iodide ◽  
Rate Constants ◽  
Methyl Esters ◽  
Ion Pairing ◽  
Stable Model ◽  
Trivalent Phosphorus ◽  
Conductivity Method ◽  
Rate Determining Step ◽  
Kinetics Of

Rates of formation and destruction of the alkoxyphosphonium ion, the intermediate in the Michaelis–Arbuzov reactions of some methyl esters of trivalent phosphorus acids with methyl iodide, are followed by a conductivity method in the solvent propylene carbonate. Specific conductances of the unstable intermediates are well estimated through stable model salts. Rate constants for both the alkylation of the reagent and the dealkylation of the intermediate are obtained. The conductivity time curves are simulated by adjusting rate constants for two sequential second order reactions, assuming no ion pairing at the concentrations used. In these measurements of the intermediate only, there is no rate-determining step; for the overall reaction the first step is in most cases rate-determining.

Absolute Rate Constants for Hydrocarbon Autoxidation. XXII. The Autoxidation of some Vinyl Compounds

1972 ◽  
Vol 50 (14) ◽  
pp. 2298-2304 ◽  
Author(s):  
J. A. Howard
Keyword(s):  
Rate Constants ◽  
Addition Reaction ◽  
Peroxy Radical ◽  
Stabilization Energy ◽  
Peroxy Radicals ◽  
Absolute Rate ◽  
Termination Rate ◽  
Vinyl Compound ◽  
Rate Constants For Addition

Absolute propagation and termination rate constants have been determined for the autoxidation of some vinyl compounds at 30°. Rates of propagation depend on the structure of both the peroxy radical and the vinyl compound. The reactivity of peroxy radicals towards addition increases as the electron-withdrawing capacity of the α-substituent increases. Rate constants for addition of t-butylperoxy radicals to vinyl compounds, [Formula: see text] fit the equation[Formula: see text]where Es is the estimated stabilization energy of the β-peroxyalkyl radical (in kcal/mol) formed in the addition reaction.

Detailed kinetics of tetrafluoroethene ozonolysis

2018 ◽  
Vol 20 (44) ◽  
pp. 28059-28067 ◽  
Author(s):  
Tam V.-T. Mai ◽  
Minh v. Duong ◽  
Hieu T. Nguyen ◽  
Lam K. Huynh
Keyword(s):  
Experimental Data ◽  
Reaction Mechanism ◽  
Kinetic Analysis ◽  
Rate Constants ◽  
Rate Model ◽  
Rate Determining Step ◽  
Calculated Rate ◽  
Detailed Kinetics ◽  
Kinetics Of

The reaction mechanism was explored at the CCSD(T)/CBS//B3LYP/aug-cc-pVTZ level. Detailed kinetic analysis was firstly carried out using an ME/RRKM rate model with the inclusion of anharmonic and tunneling treatments. 1,3-Cycloaddition is found to be the rate-determining step. Calculated rate constants confirm the latest experimental data.

Metal Complexes as Antioxidants. I. The Reaction of Zinc Dialkyldithiophosphates and Related Compounds with Peroxy Radicals

1973 ◽  
Vol 51 (10) ◽  
pp. 1543-1553 ◽  
Author(s):  
J. A. Howard ◽  
Y. Ohkatsu ◽  
J. H. B. Chenier ◽  
K. U. Ingold
Keyword(s):  
Electron Transfer ◽  
Metal Complexes ◽  
Rate Constants ◽  
Initial Rate ◽  
Peroxy Radicals ◽  
Zinc Dialkyldithiophosphates ◽  
Zinc Diethyldithiocarbamate ◽  
Inhibition Studies ◽  
Kinetics Of ◽  
Related Compounds

The kinetics of the inhibition of the autoxidation of several hydrocarbons by a number of zinc dialkyldithiophosphates and by zinc isopropylxanthate and zinc diethyldithiocarbamate have been studied at 30c and at 50c. The oxidations were generally auto-retarding but initial rate measurements showed that these compounds trapped peroxy radicals and allowed rate constants for this process to be calculated. Rate constants for the reaction of t-butylperoxy radicals with these compounds have been measured by a kinetic e.p.r. method in the temperature range 0c to −90c. Extrapolation of the e.p.r. data to the temperatures of the inhibition studies showed that the various experimental procedures yielded results in satisfactory agreement with one another.It is suggested that the reaction of peroxy radicals with zinc complexes involves reaction at the metal center either by an electron transfer or an SH2 process.

Effect of pH on the reaction of 1,3-dihydro-1-hydroxy-3-oxo-1,2-benziodoxole with 2-mercaptoethanol, 2-mercaptoethylamine, and glutathione

1970 ◽  
Vol 48 (19) ◽  
pp. 3104-3107 ◽  
Author(s):  
James Leslie
Keyword(s):  
Rate Constants ◽  
Ionic Species ◽  
Second Order ◽  
Hydrogen Ion ◽  
Effect Of Ph ◽  
Order Rate ◽  
Rate Determining Step ◽  
Ion Activity ◽  
Kinetics Of ◽  
Linear Manner

The kinetics of the oxidation of 2-mercaptoethanol, 2-mercaptoethylamine, and glutathione with 1,3-dihydro-1-hydroxy-3-oxo-1,2-benziodoxole (1) have been examined at pH 4–5.6. The reaction is second-order, which can be explained by a rate-determining step involving the reaction of one molecule of the thiol with one molecule of 1. The second-order rate constants vary in a linear manner with the reciprocal of the hydrogen ion activity. The ionic species involved in the reaction are discussed.

Sign in / Sign up

Export Citation Format

Share Document