Synthetic application of α-hydroxydiazene systems. II. Uncatalyzed and phenol catalyzed radical chain hydro-tert-butylation of unsaturated compounds with tert-butylazodiphenylcarbinol

1976 ◽  
Vol 54 (9) ◽  
pp. 1345-1348 ◽  
Author(s):  
Dominic W. K. Yeung ◽  
John Warkentin
Keyword(s):  
Benzene Solution ◽  
Chain Process ◽  
The Novel ◽  
Radical Chain ◽  
Tert Butyl ◽  
Radical Adduct ◽  
Butyl Radical ◽  
A Chain ◽  
Radical Traps ◽  
Synthetic Application

tert-Butylazodiphenylcarbinol 1 decomposes in benzene solution by a chain mechanism involving tert-butyl radicals. Many olefinic compounds and azobenzene act as radical traps and are hydro-tert-butylated by 1. The regiochemistry of hydro-tert-butylation of unsymmetric alkenes is that expected for a mechanism which involves addition of tert-butyl radical so as to form the most stable radical adduct, which subsequently abstracts hydrogen from 1.In some cases phenol acts as a catalyst for the hydroalkylation process. The novel catalytic effect of phenol in a radical chain process is attributed to the favourable thermochemistry for induced, concerted decomposition of 1 by radical attack at hydroxyl hydrogen.

RADIATION-INDUCED CHANGES IN THE UNSATURATION OF POLYISOPRENE

1965 ◽  
Vol 43 (10) ◽  
pp. 2772-2785 ◽  
Author(s):  
Morton. A. Golub ◽  
Jeanne. Danon
Keyword(s):  
Energy Transfer ◽  
Solid State ◽  
Benzene Solution ◽  
Chain Process ◽  
Energy Transfer Mechanism ◽  
Carbonium Ions ◽  
Intermolecular Energy ◽  
Radiation Induced ◽  
A Chain ◽  
Induced Changes

Polyisoprene in the solid state and in benzene solution undergoes radiation-induced cis-trans isomerization and loss of unsaturation. Starting with various cis or trans polymers, the isomerization approaches an equilibrium in which the cis/trans ratio is around 50/50 for polyisoprenes irradiated in solution or in the solid state. The G(isom.) values for either cis → trans or trans → cis isomerization, i.e., the number of cis (or trans) units isomerized initially per 100 eV absorbed by both polymer and solvent, in 1% solution, and by polymer alone, in the solid state, are about 1.0 and 10, respectively. The energy transfer mechanism proposed previously for polybutadiene and squalene isomerization is assumed to hold for polyisoprene as well. The loss of unsaturation in films irradiated with electrons under nitrogen is twice as rapid as in films γ-irradiated in vacuo, the G(-d.b.) (d.b. = double bond) values being 13.4 and 6.7, respectively. Correspondingly, G(-d.b.) for a γ-irradiated solution is 27, calculated in terms of energy absorbed directly by the polymer; intermolecular energy transfer is again indicated, although phenylation may also contribute to the loss of double bonds in solution. The large drop in unsaturation in solution and in the solid state is attributed to a chain process involving cyclization and some cross-linking, with the participation of both free radicals and carbonium ions. Work with polyisoprene-3-d confirmed the importance of isomerization and loss of unsaturation and gave an activation energy of 1.1 kcal/mole for the latter reaction.

A kinetic study of the reaction of adamantanethione with 2-adamantanethiol

1976 ◽  
Vol 54 (21) ◽  
pp. 3407-3411 ◽  
Author(s):  
J. C. Scaiano ◽  
J. P.-A. Tremblay ◽  
K. U. Ingold
Keyword(s):  
Benzene Solution ◽  
Hydrogen Abstraction ◽  
Chain Process ◽  
Radical Chain ◽  
Diffusion Controlled ◽  
Carbon Centered Radical ◽  
Photochemical Initiation ◽  
Kinetics Of ◽  
Radical Chain Process ◽  
Termination Process

The title reaction is a free radical chain process which yields di(2-adamantyl)disulfide(2). The kinetics of this reaction have been studied in benzene solution at 50 °C using both thermal and photochemical initiation. Thermal initiators which yield resonance stabilized carbon-centered radicals were surprisingly inefficient at starting the reaction. The kinetics indicate that the rate controlling propagation step is hydrogen abstraction from the thiol, AdHSH, by the carbon-centered radical, AdHSSAd•. Rotating sector studies gave a rate constant for this step, k2 = 4 × 104 M−1 s−1. There is some kinetically first order chain termination, but the predominant termination process involves the diffusion-controlled bimolecular self-reactions of AdHSSAd• radicals, 2kt = 1.8 × 1010 M−1 s−1.

Azaborolyl-Komplexe, 27 / Azaborolyl Complexes, 27

1992 ◽  
Vol 47 (5) ◽  
pp. 635-639 ◽  
Author(s):  
Günter Schmid ◽  
Wolfgang Meyer-Zaika
Keyword(s):  
Mass Spectrometry ◽  
Benzene Solution ◽  
Stable Complex ◽  
Intramolecular Rearrangement ◽  
The Novel ◽  
Intramolecular Coordination ◽  
Tert Butyl ◽  
Nmr Data ◽  
Stereoselective Reactions ◽  
Ab Ring

Alkenyl substituted 1H-1,2-azaborolyl (Ab) complexes are promising candidates for stereoselective reactions, due to the chirality of the AbM moiety and the intramolecular coordination of the alkenyl group to the metal atom. The synthesis of [1-tert-butyl-2-methy1-3-(4-penten- l -y1)-η5-1H-1,2-azaborolyl]-bis(triphenylphosphine)rhodium (3) is achieved by the reaction of AbLi (2) [from AbH (1)] with (Ph3P)3RhCl. In benzene solution one PPh3 ligand of 3 is substituted by the C=C group of the pentenyl substituent. Simultaneously the η5-coordination of the Ab ring changes to an allylic η3-coordination forming 4. Steric reasons seem to be responsible for this intramolecular rearrangement. The shorter 2-propen-1-yl substituent is unable to act in the same way and therefore only forms the stable complex [1-tert-butyl-2-methyl-3-(2-propen- l -yl)-η5-1H-1,2-azaborolyl]-bis(triphenylphosphine)rhodium (7). Mass spectrometry, 1H, 11B and 31P NMR data were used to characterize the novel complexes.

Metal complexes as antioxidants. IV. Reaction of cupric dialkyldithiophosphates and dialkyldithiocarbamates with alkyl hydroperoxides

1977 ◽  
Vol 55 (10) ◽  
pp. 1644-1652 ◽  
Author(s):  
Joseph Hector Bernard Chenier ◽  
James Anthony Howard ◽  
John Charles Tait
Keyword(s):  
Time Profile ◽  
Second Order ◽  
Initial Reaction ◽  
Chain Process ◽  
Peroxy Radicals ◽  
Radical Chain ◽  
Butyl Hydroperoxide ◽  
Tert Butyl ◽  
Tert Butyl Hydroperoxide ◽  
Alkylperoxy Radicals

The initial reaction of cupric dialkyldithiophosphates and dialkyldithiocarbamates with tert-butyl hydroperoxide and α-cumyl hydroperoxide is a free radical chain process. Initiation is achieved by a redox reaction between the complex and the hydroperoxide to give alkoxy and alkylperoxy radicals. The alkoxy radicals then abstract a hydrogen from excess hydroperoxide to give alkylperoxy radicals. The cupric complexes are converted to copper sulphate by reaction with peroxy radicals while the hydroperoxide is reduced to alcohol. About 5 mol of hydroperoxide are decomposed by each mole of complex. The decomposition of tert-butyl hydroperoxide then stops whereas complete destruction of α-cumene hydroperoxide occurs by a heterogeneous ionic reaction.The kinetics of the initial reaction are second-order for both complexes. The dithiophosphate reaction is first-order in each reactant while the dithiocarbamate reaction is zero-order in the complex concentration and second-order in the hydroperoxide concentration. Simple kinetics, however, only hold for the initial rates of complex disappearance. Total dithiophosphate decomposition exhibits three stages, an initial fast reaction followed by an induction period and a rapid third stage. The concentration–time profile for dithiocarbamate decomposition is quite different and the overall rate of reaction in some instances increases as the complex concentration decreases.

The pyrolytic reactions of acetaldehyde in presence of nitric oxide

1958 ◽  
Vol 245 (1243) ◽  
pp. 456-469 ◽  
Keyword(s):  
Nitric Oxide ◽  
Hydrogen Abstraction ◽  
Chain Process ◽  
Molecular Rearrangement ◽  
Radical Chain ◽  
Low Concentrations ◽  
Rearrangement Mechanism ◽  
A Chain ◽  
Induced Decomposition ◽  
Radical Chain Process

Except at very low concentrations where a slight inhibition is observable nitric oxide strongly catalyses the decomposition of acetaldehyde. The rate of the induced reaction is approximately proportional to [aldehyde] 3/2 [NO] ½ . The ratio of nitric oxide consumed to aldehyde decomposed remains small even in conditions where the corresponding ratio for the nitric-oxide-induced ether decomposition approaches unity. The induced decomposition is reduced in rate to a limit by the addition of propylene. From kinetic and analytical measurements it is concluded that the thermal acetaldehyde decomposition occurs partly by a molecular rearrangement mechanism and partly by a radical chain process. The catalysis by nitric oxide involves a chain reaction initiated by hydrogen abstraction, and probably also an acceleration of the molecular process under the influence of collisions with the nitric oxide. The steps of the nitric-oxide-induced chain process are discussed.

Persuasion: Fellow Creatures

2017 ◽  
Author(s):  
Pam Morris
Keyword(s):  
The Self ◽  
The Novel ◽  
Class Relations ◽  
Narrative Perspective ◽  
Class Hierarchies ◽  
A Chain ◽  
Porous Boundaries

Persuasion overtly foregrounds the self as embodied: physical accidents and sickness are recurrent. Sir Walter Eliot’s belief in the time-defying bodily grace of nobility is subject to Austen’s harshest irony. The transition from vertically ordered place to horizontal space in Persuasion is more extreme than in any other of the completed novels. Anne Elliot’s movement from social exclusiveness to socially inclusive possibility allows Austen to challenge gender and class hierarchies traditionally held to be inborn. Her writerly experimentation expands the possibilities of narrative perspective to encompass the porous boundaries of the physical, the emotional and the rational that constitute any moment of consciousness. Her focalisation techniques in the text look directly towards Woolf’s stylist innovations. A chain of references to guns and shooting gathers into the novel contentious contemporary discursive networks on class relations, notions of masculinity and the nature of creaturely life.

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