Absolute rate constants for hydrocarbon autoxidation. XVIII. Oxidation of some acyclic ethers

1970 ◽  
Vol 48 (6) ◽  
pp. 873-880 ◽  
Author(s):  
J. A. Howard ◽  
K. U. Ingold
Keyword(s):  
Rate Constants ◽  
Propagation Rate ◽  
Phenyl Ether ◽  
Isopropyl Ether ◽  
Benzyl Ether ◽  
Absolute Rate ◽  
Butyl Ether ◽  
Termination Rate ◽  
Benzyl Phenyl Ether

Propagation and termination rate constants have been measured for autoxidation of benzyl phenyl ether, benzyl-t-butyl ether, isopropyl ether, and benzyl ether. In the case of isopropyl ether and benzyl ether, estimates have been made of inter- and intramolecular propagation rate constants. Reactivities of acyclic ethers towards the t-butylperoxy radical have been determined. Rate constants for autoxidation of cyclic and acylic ethers have been summarized and compared.

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.

ABSOLUTE RATE CONSTANTS FOR HYDROCARBON AUTOXIDATION: II. DEUTERO STYRENES AND RING-SUBSTITUTED STYRENES

1965 ◽  
Vol 43 (10) ◽  
pp. 2737-2743 ◽  
Author(s):  
J. A. Howard ◽  
K. U. Ingold
Keyword(s):  
Rate Constants ◽  
Isotope Effects ◽  
Peroxy Radical ◽  
Propagation Rate ◽  
Chain Termination ◽  
Absolute Rate ◽  
First Order ◽  
Oxidation Rates ◽  
Deuterium Substitution ◽  
Termination Process

The effect of deuterium substitution on the absolute rate constants for the bimolecular chain termination process in the oxidation of styrene indicates that the α-hydrogen is abstracted in this reaction. The first order chain termination process is suppressed both by deuteration of styrene at the α-position and by the addition of heavy water. A possible mechanism for this termination is proposed. There appear to be small secondary deuterium isotope effects in the propagation reaction.The overall oxidation rates and the propagation rate constants are increased by the addition to the aromatic ring of both electron-attracting and electron-releasing substituents. This is attributed in the former case to the increased stability of the resulting styryl radicals and in the latter case to the increased stability of a dipolar transition state. In hydrogen atom abstraction from 2,6-di-t-butyl-4-methylphenol, the peroxy radical from 3-chlorostyrene is more reactive than that from styrene which, in turn, is more reactive than the peroxy radical from 4-methoxy-styrene.

ABSOLUTE RATE CONSTANTS FOR HYDROCARBON AUTOXIDATION: III. α-METHYLSTYRENE, β-METHYLSTYRENE, AND INDENE

1966 ◽  
Vol 44 (10) ◽  
pp. 1113-1118 ◽  
Author(s):  
J. A. Howard ◽  
K. U. Ingold
Keyword(s):  
Isotope Effect ◽  
Rate Constant ◽  
Rate Constants ◽  
Propagation Rate ◽  
Absolute Rate ◽  
Order Process ◽  
Deuterium Isotope Effect ◽  
First Order ◽  
Process Rate Constant ◽  
Propagation Rate Constant

Absolute rate constants for the copolymerization of α-methylstyrene and oxygen have been measured from 13 to 50 °C. The propagation and termination rate constants can be represented by[Formula: see text]Experiments with 2,6-di-t-butyl-4-methylphenol at 65 °C have shown that C6H5C(CH3):CH2 and C6H5C(CD3):CD2 have the same propagation rate constant but that chain termination involves a deuterium isotope effect (kt)H/(kt)D ≈ 1.5.Absolute rate constants for the copolymerization of oxygen with β-methylstyrene and with indene at 30 °C showed that a significant fraction of the oxidation chains were terminated by a kinetically first order process (rate constant kx). The rate constants for β-methylstyrene and indene at 30 °C are kp = 51 and 142 l mole−1 s−1, kt = 1.6 × 107 and 2.5 × 107 l mole−1 s−1, and kx = 0.61 and 1.2 s−1, respectively. The propagation rate constant for indene can be separated into a rate constant for the copolymerization with oxygen (kadd = 128 l mole−1 s−1) and a rate constant for hydrogen atom abstraction (kabstr = 14 l mole−1 s−1). In the presence of heavy water the first order process for indene had a deuterium isotope effect (kx)/(kx)D2O ≈ 3.

Absolute rate constants for hydrocarbon autoxidation. XVII. The oxidation of some cyclic ethers

1969 ◽  
Vol 47 (20) ◽  
pp. 3809-3815 ◽  
Author(s):  
J. A. Howard ◽  
K. U. Ingold
Keyword(s):  
Hydrogen Atom ◽  
Rate Constants ◽  
Transfer Rate ◽  
Chain Transfer ◽  
Hydrogen Atom Abstraction ◽  
Cyclic Ethers ◽  
Peroxy Radicals ◽  
Absolute Rate ◽  
Termination Rate

The propagation and termination rate constants have been determined for the autoxidation of 1,4-dioxan, tetrahydropyran, tetrahydrofuran, 2,5-dimethyltetrahydrofuran, and phthalan. The rate constants for α-hydrogen atom abstraction from some of the ethers by the tetralylperoxy radical and from tetralin by some ether peroxy radicals have been measured and compared. The chain transfer rate constants have been estimated for the reaction of the cumylperoxy radical with α-hydroperoxytetrahydrofuran, α-hydroperoxytetrahydropyran, and α-ethoxyethyl hydroperoxide.

Quantitative studies of the autoxidation of linoleate monomers sequestered in phosphatidylcholine bilayers. Absolute rate constants in bilayers

1985 ◽  
Vol 63 (10) ◽  
pp. 2633-2638 ◽  
Author(s):  
Lawrence Ross Coates Barclay ◽  
Steven Jeffrey Locke ◽  
Joseph Mark MacNeil ◽  
Joann Vankessel
Keyword(s):  
Linoleic Acid ◽  
Methyl Linoleate ◽  
Rate Constant ◽  
Rate Constants ◽  
Homogeneous Solution ◽  
Propagation Rate ◽  
Water Soluble ◽  
Peroxyl Radicals ◽  
Absolute Rate ◽  
Hydrophobic Region

The kinetics of autoxidation of linoleic acid in dimyristoylphosphatidylcholine (DMPC) bilayers were studied at 30 °C and pH 7 under 760 Torr O2. Reactions were initiated using either the lipid-soluble di-tert-butylhyponitrite (DBHN) or water-soluble azobis(2-amidinopropane)•HCl (ABAP). Rates of chain initiation, Ri, were measured with a lipid-soluble antioxidant, a-tocopherol, or a water-soluble one, 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylate (Trolox). The slightly higher oxidizability obtained [Formula: see text] compared to methyl linoleate in chlorobenzene [Formula: see text] is attributed to a moderate polar solvent effect on ionized linoleate near the bilayer surface. A low initiator efficiency, e = 0.0895 for DBHN in DMPC, is attributed to the cage effect in the bilayer of high microviscosity. Similar autoxidation experiments on methyl linoleate in DMPC bilayers gave a lower oxidizability [Formula: see text], indicating that the ester is sequestered deeper in the hydrophobic region of DMPC than is ionized linoleate. Some absolute rate constants are determined using the rotating sector technique for linoleic acid in 0.50 M SDS micelles, and egg lecithin and dilinoleoylphosphatidylcholine (DLPC) bilayers. A hundredfold decrease in the termination rate constant, 2kt for DLPC bilayer compared to homogeneous solution is attributed to chain termination in a bilayer region of high polarity. A concomitant reduction (up to tenfold) in the propagation rate constant, kp, is attributed to diffusion of polar peroxyl radicals away from the oxidizable region of the bilayer.

Absolute rate constants for hydrocarbon autoxidation. XIX. Oxidation of some α-substituted toluenes

1970 ◽  
Vol 48 (14) ◽  
pp. 2165-2172 ◽  
Author(s):  
J. A. Howard ◽  
S. Korcek
Keyword(s):  
Liquid Phase ◽  
Rate Constants ◽  
Bromine Atom ◽  
Peroxy Radical ◽  
Phenyl Radical ◽  
Absolute Rate ◽  
Termination Rate ◽  
Substituted Toluenes

Absolute propagation and termination rate constants have been measured for the liquid phase autoxidation of some α-substituted toluenes at 30 °C. Rate constants for reaction of α-substituted toluenes with their own peroxy radical and with the t-butylperoxy radical have been compared. It would appear that the reactivity of an α-substituted benzylperoxy radical depends on the nature of the α-substituent.Reactivities of α-substituted toluenes towards the t-butylperoxy radical, the bromine atom, and the phenyl radical have been compared.

Absolute rate constants for hydrocarbon autoxidation. XIII. Aldehydes: photo-oxidation, co-oxidation, and inhibition

1969 ◽  
Vol 47 (16) ◽  
pp. 3017-3029 ◽  
Author(s):  
G. E. Zaikov ◽  
J. A. Howard ◽  
K. U. Ingold
Keyword(s):  
Rate Constants ◽  
Cumene Hydroperoxide ◽  
Propagation Rate ◽  
High Reactivity ◽  
Peroxy Radicals ◽  
Absolute Rate ◽  
Product Analysis ◽  
Hydroperoxy Radical ◽  
Great Ease ◽  
Absolute Rate Constant

The oxidations of acetaldehyde, heptanal, octanal, cyclohexanecarboxaldehyde, pivaldehyde, and benzaldehyde in chlorobenzene at 0 °C have been studied. These aldehydes oxidize at similar rates under similar conditions because there are compensating changes in the rate constants for chain propagation (kp) and chain termination (2kt). The termination rate constants increase from ∼7 × 106 M−1 s−1 for pivaldehyde and cyclohexanecarboxaldehyde to ∼2 × 109 M−1 s−1 for benzaldehyde. The propagation rate constants increase from ∼1 × 103 M−1 s−1 for pivaldehyde to ∼1 × 104 M−1 s−1 for benzaldehyde.The rate of oxidation of the aldehydes was decreased by the addition of 1,4-cyclohexadiene, tetralin, tetralin hydroperoxide, cumene, cumene hydroperoxide, t-butyl hydroperoxide, and 2,6-di-t-butyl-4-methylphenol. As a result of product analysis and absolute rate constant measurements, it is concluded that the peroxy radicals derived from aldehydes are considerably more reactive in hydrogen atom abstraction from hydrocarbons than are the peroxy radicals derived from the hydrocarbons. In the abstraction from cyclohexadiene, the acylperoxy radicals appear to be from 15 to 70 times as reactive, and the benzoylperoxy radicals about 800–900 times as reactive, as the hydroperoxy radical. The differences in reactivity are very much less pronounced in the abstraction from 2,6-di-t-butyl-4-methylphenol.The great ease of oxidation of all aldehydes, and particularly benzaldehyde, is due at least in part to the high reactivity of the peroxy radicals formed in these reactions.

Absolute rate constants for hydrocarbon autoxidation. XIV. Termination rate constants for tertiary peroxy radicals

1969 ◽  
Vol 47 (20) ◽  
pp. 3793-3795 ◽  
Author(s):  
J. A. Howard ◽  
K. Adamic ◽  
K. U. Ingold
Keyword(s):  
Electron Spin Resonance ◽  
Rate Constants ◽  
Chain Termination ◽  
Peroxy Radicals ◽  
Absolute Rate ◽  
Termination Rate ◽  
Spin Resonance ◽  
After Effect ◽  
Effect Method ◽  
Good Agreement

Absolute rate constants for chain termination by ten t-peroxy radicals have been measured at 30° by the rotating sector technique, the photochemical pre- and after-effect method, and by electron spin resonance. The different methods generally give results in good agreement with one another. The termination rate constants vary from a low of ∼4 × 102 M−1 s−1 for t-butylperoxy to a high of ∼3 × 104 M−1 s−1 for 1,1-diphenylethylperoxy radicals.

ChemInform Abstract: ABSOLUTE RATE CONSTANTS FOR REACTIONS OF PHENYL RADICALS

1978 ◽  
Vol 9 (20) ◽  
Author(s):  
V. MADHAVAN ◽  
R. H. SCHULER ◽  
R. W. FESSENDEN
Keyword(s):  
Rate Constants ◽  
Absolute Rate ◽  
Phenyl Radicals
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