Absolute rate constants for hydrocarbon autoxidation. 32. On the self-reaction of 1,1-diphenylethylperoxyl in solution

1982 ◽  
Vol 60 (20) ◽  
pp. 2566-2572 ◽  
Author(s):  
J. A. Howard ◽  
J. H. B. Chenier ◽  
T. Yamada
Keyword(s):  
Free Radical ◽  
Rate Constants ◽  
The Self ◽  
Absolute Rate ◽  
Radical Process ◽  
First Order ◽  
Hydroperoxide Decomposition ◽  
Solvent Cage ◽  
Induced Decomposition ◽  
Free Radical Process

The major products of the self-reaction of 1,1-diphenylethylperoxyl have been determined from product studies of the autoxidation of 1,1-diphenylethane, induced decomposition of 1,1-diphenylethyl hydroperoxide, and decomposition of 2,2,3,3-tetraphenylbutane under an atmosphere of oxygen. Overall self-reaction is a complex free-radical process involving the intermediacy of 1,1-diphenylethoxyl and 1-phenyl-1-phenoxyethoxyl which undergo H-atom abstraction, β-scission and, in the case of the former radical, rearrangement. Hydroperoxide decomposition under an atmosphere of 36O2 has shown that 1,1-diphenylethylperoxyl undergoes β-scission faster than α-cumylperoxyl at 303 K in solution. The values of the rate constants for self-reaction of Ph2C(Me)O2• relative to those for tert-butylperoxyl are, however, not affected by this reaction. Furthermore they are not affected to any appreciable extent by the efficiency with which Ph2C(Me)O•, formed in nonterminating self-reactions, escape from the solvent cage. They are influenced principally by the first-order rate of decomposition of Ph2C(Me)OOOOC(Me)Ph2.

Absolute rate constants for hydrocarbon autoxidation. 33. A product study of the self-reaction of α-tetralylperoxyls in solution

1983 ◽  
Vol 61 (9) ◽  
pp. 2037-2043 ◽  
Author(s):  
A. Baignée ◽  
J. H. B. Chenier ◽  
J. A. Howard
Keyword(s):  
Steady State ◽  
Free Radical ◽  
Rate Constant ◽  
Rate Constants ◽  
The Self ◽  
Absolute Rate ◽  
Chain Reaction ◽  
Low Concentrations ◽  
A Chain ◽  
Product Study

The major initial products of the self-reaction of α-tetralylperoxyls (C10H11O2•) in chlorobenzene at 303–353 K are equal concentrations of α-tetralol and α-tetralone in ~90% yield based on the number of initiating radicals. These yields are consistent with the non-radical (Russell) mechanism for self-reaction. Low concentrations of bis(α-tetralyl) peroxide are produced, indicating that there is a small but detectable free-radical contribution towards termination. C10H11O2• undergoes β-scission in this temperature range but steady-state concentrations of C10H11• are too low to influence the termination rate constant 2kt, or react with C10H11O2• to give (C10H11O2. α-Tetralol to α-tetralone ratios and total yields of these products are significantly less than 1 and 100%, respectively, in methanol and acetonitrile. Formaldehyde is produced in methanol indicating the involvement of α-hydroxymethylperoxyls, derived from the solvent, in termination. There is no evidence for a chain reaction or a zwitterion intermediate for self-reaction of C10H11O2• in solution.

Pyrolysis of Aryl Azides.X. Effects of Azide Concentration on Rate Constants and Product Yields

1990 ◽  
Vol 43 (6) ◽  
pp. 997 ◽  
Author(s):  
LK Dyall ◽  
PAS Smith
Keyword(s):  
Free Radical ◽  
Rate Constants ◽  
Aryl Azides ◽  
Radical Chain ◽  
Initial Concentration ◽  
Azo Compound ◽  
Product Yields ◽  
First Order ◽  
Induced Decomposition ◽  
Group Effects

First-order rate constants (k1) have been measured for pyrolysis of azidobenzenes in decalin solution, in the presence of a free-radical chain inhibitor to prevent any induced decomposition. The new values of k1 for the spontaneous unimolecular thermolysis are lower than previously reported ones, and require revision of published neighbouring group effects. Product yields ( azo compound and primary amine) vary with initial concentration of azide in ways which suggest the species responsible for induced decomposition is not triplet arylnitrene , but a solvent-derived free radical. There is no evidence for induced decomposition when nitrobenzene is the solvent. For aryl azides with no neighbouring group effects operating in their pyrolysis, the Arrhenius parameters Eact and ΔSactobey a precise linear relationship.

Absolute rate constants for hydrocarbon autoxidation. XV. The induced decomposition of some t-hydroperoxides

1969 ◽  
Vol 47 (20) ◽  
pp. 3797-3801 ◽  
Author(s):  
J. A. Howard ◽  
K. U. Ingold
Keyword(s):  
Isotope Effect ◽  
Rate Constant ◽  
Rate Constants ◽  
The Self ◽  
Absolute Rate ◽  
Alkoxy Radical ◽  
Deuterium Isotope Effect ◽  
Alkoxy Radicals ◽  
Induced Decomposition ◽  
Alkylperoxy Radicals

The radical induced decomposition of several t-hydroperoxides at 30° has been studied. In the self reaction of t-alkylperoxy radicals the ratio of the rates of alkoxy radical diffusion from the cage to combination in the cage is essentially independent of the size of the t-alkyl group.The rate constant for abstraction from hydroperoxides of the hydroperoxidic hydrogen by alkoxy radicals is about 4 × 106 M−1 s−1 at 30°. This reaction has a deuterium isotope effect, kH/kD ≈ 5.The 1,1-diphenylethoxy radical undergoes a 1,2-phenyl shift to yield the 1-phenyl-1-phenoxyethyl radical more rapidly that it undergoes β-scission.

Determination of the Absolute Rate Constants in Free-Radical Polymerization of Zwitterionic Sulfobetaine Monomers

1993 ◽  
Vol 30 (1) ◽  
pp. 51-58 ◽  
Author(s):  
Der-jang Liaw ◽  
Jen-rong lin ◽  
Kwang-chih Chung
Keyword(s):  
Free Radical ◽  
Radical Polymerization ◽  
Rate Constants ◽  
Free Radical Polymerization ◽  
Absolute Rate ◽  
The Absolute

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.

scholarly journals Determination of the Absolute Rate Constants for Free-Radical Polymerization

1981 ◽  
Vol 13 (5) ◽  
pp. 453-457 ◽  
Author(s):  
Kuo Jen-Feng ◽  
Chen Chuh-Yung
Keyword(s):  
Free Radical ◽  
Radical Polymerization ◽  
Rate Constants ◽  
Free Radical Polymerization ◽  
Absolute Rate ◽  
The Absolute

Hydrogels based on pullulan derivatives crosslinked via a “living” free-radical process

2002 ◽  
Vol 203 (10-11) ◽  
pp. 1285-1291 ◽  
Author(s):  
Vittorio Crescenzi ◽  
Mariella Dentini ◽  
Debora Bontempo ◽  
Giancarlo Masci
Keyword(s):  
Free Radical ◽  
Radical Process ◽  
Free Radical Process
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