Reaction of t-Butoxy Radicals With Cyclic Alkenes Studied by the Nitroxide Radical-Trapping Technique

1991 ◽  
Vol 44 (10) ◽  
pp. 1407 ◽  
Author(s):  
WK Busfield ◽  
DI Grice ◽  
ID Jenkins ◽  
SH Thang
Keyword(s):  
Reaction Pathway ◽  
Nitroxide Radical ◽  
Radical Addition ◽  
Reaction Pathways ◽  
Allylic Substitution ◽  
Major Pathway ◽  
Radical Trapping ◽  
Major Reaction ◽  
Minor Reaction ◽  
Cyclic Alkenes

The pattern of reactions occurring between t- butoxy radicals and a number of cyclic alkenes has been investigated by the nitroxide radical-trapping technique. The major reaction pathway is allylic abstraction unless this position is at a bridgehead as in norbornene where the major pathway is radical addition. The technique is sufficiently sensitive to identify minor reaction pathways of non-allylic substitution and radical addition when in the presence of extensive allylic substitution. Some stereoselective effects are also detected.

ChemInform Abstract: Reaction of t-Butoxy Radicals with Cyclic Alkenes Studied by the Nitroxide Radical-Trapping Technique.

ChemInform ◽  
2010 ◽  
Vol 23 (3) ◽  
pp. no-no
Author(s):  
W. K. BUSFIELD ◽  
D. I. GRICE ◽  
I. D. JENKINS ◽  
S. H. THANG
Keyword(s):  
Nitroxide Radical ◽  
Radical Trapping ◽  
Cyclic Alkenes

The Chemistry of the Zinc Oxide Cure of Halobutyl

1984 ◽  
Vol 57 (4) ◽  
pp. 813-825 ◽  
Author(s):  
I. Kuntz ◽  
R. L. Zapp ◽  
R. J. Pancirov
Keyword(s):  
Zinc Oxide ◽  
Zinc Chloride ◽  
Reaction Pathway ◽  
Diels Alder ◽  
Crosslinking Reaction ◽  
Conjugated Diene ◽  
Carbon Carbon Bonds ◽  
Carbon Bonds ◽  
Chloride Catalyst ◽  
Major Reaction

Abstract The studies described in this papier lead to certain conclusions. The crosslinking reaction of halobutyl with zinc oxide does not give rise to ether crosslinks. All the evidence indicates that the chemistry involves the formation of carbon-carbon bonds by an alkylation type chemistry. The dehydrohalogenation of the halobutyl to form a zinc chloride catalyst is a key feature of the crosslinking chemistry. But conjugated diene butyl and Diels-Alder reactions are not the major reaction pathway for the zinc oxide crosslinking reaction. These conclusions have significance for the zinc oxide cure of CR which has an active allylic halide structure formed by 1,2-monomer enchainment.

One-step hydroprocessing of fatty acids into renewable aromatic hydrocarbons over Ni/HZSM-5: insights into the major reaction pathways

2017 ◽  
Vol 19 (4) ◽  
pp. 2961-2973 ◽  
Author(s):  
Shiyou Xing ◽  
Pengmei Lv ◽  
Jiayan Wang ◽  
Junying Fu ◽  
Pei Fan ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Aromatic Hydrocarbons ◽  
Reaction Pathways ◽  
Major Reaction ◽  
One Step ◽  
Catalytic Mechanisms

We describe the production of renewable aromatic hydrocarbons by a new facile one-step hydroprocessing of fatty acids with an in-depth exploration of the major reaction pathways and catalytic mechanisms.

Reaction Pathways to 2-Aminothiophenes and Thiophene-3-carbonitriles

2009 ◽  
Vol 62 (5) ◽  
pp. 402 ◽  
Author(s):  
Luigi Aurelio ◽  
Bernard L. Flynn ◽  
Peter J. Scammells
Keyword(s):  
Comparative Studies ◽  
Reaction Pathway ◽  
Reaction Pathways ◽  
Synthesis And Characterization ◽  
The Past ◽  
Adenosine A1 ◽  
Unexpected Reaction ◽  
Potential Applications ◽  
A1 Receptor

Over the past two decades 2-amino-3-benzoylthiophenes have been found to act as allosteric enhancers of the adenosine A1 receptor (A1AR). As such, compounds of this type have potential applications in the therapy of a variety of disorders by enhancing A1AR activation. Initial studies in this field identified various 2-amino-3-benzoylthiophenes as potential leads and of these PD 81723 1a has become the benchmark for comparative studies due to its favourable ratio of allosteric enhancement to antagonism. Surprisingly the synthesis and characterization of PD 81723 1a has not been previously reported. Herein we report the synthesis and characterization of this important A1AR allosteric enhancer. As part of this study we also found an unexpected reaction pathway to 2-phenylthiophene-3-carbonitriles.

Back Cover: Insights into the Major Reaction Pathways of Vapor-Phase Hydrodeoxygenation of m -Cresol on a Pt/HBeta Catalyst (ChemCatChem 3/2016)

ChemCatChem ◽  
2016 ◽  
Vol 8 (3) ◽  
pp. 656-656
Author(s):  
Qianqian Sun ◽  
Guanyi Chen ◽  
Hua Wang ◽  
Xiao Liu ◽  
Jinyu Han ◽  
...  
Keyword(s):  
Vapor Phase ◽  
Reaction Pathways ◽  
Back Cover ◽  
Major Reaction

1999 R.U. Lemieux Award Lecture Adventures with azo-, azoxy-, and hydrazoarenes: from the Wallach to the benzidine rearrangement. Molecular electronics

2000 ◽  
Vol 78 (10) ◽  
pp. 1251-1271 ◽  
Author(s):  
Erwin Buncel
Keyword(s):  
Molecular Electronics ◽  
Rate Constant ◽  
Reaction Pathway ◽  
Solvent Polarity ◽  
Molecular Switch ◽  
Reaction Pathways ◽  
Optical Data ◽  
Constant Ratio ◽  
Rate Constant Ratio ◽  
Acid Catalyzed

The author's studies with aromatic azo-, azoxy-, and hydrazo-dye molecules, comprising kinetic and equilibrium investigations, as well as synthesis of novel molecules having photogenic properties, are described under the following highlights: A. Wallach rearrangement and cognate studies with azoxyarenes — (1) Elucidation of the mechanism of the Wallach rearrangement of azoxybenzene through the kinetic observation of a two-proton process which, together with a pKa study, was interpreted on the basis of formation of a deoxygenated, dicationic, symmetrical species as a key, short-lived reaction intermediate. (2) The proposal of a general acid-catalyzed pathway in concentrated sulfuric acid (catalysis by H2SO4 and H3SO+4. (3) Elucidation of the consecutive sulfonations of reaction products of azoxybenzene in the 100% H2SO4 region, and the diprotonation equilibria for p-hydroxyazobenzene, thus shedding light on past reaction pathway and product studies. (4) The observation of a novel reaction pathway for 2,4,6,2',4',6'-hexamethy lazoxybenzene. (5) The observation of a dichotomy of reaction pathways for α- and β-2-phenylazoxynaphthalenes: reaction via the dicationic intermediate and via quinoid intermediate species; comprising two isomeric compounds reacting by different pathways to give the same product. (6) Identification and structure proof of α- and β-isomers observed for the first time in the peracid oxidation of phenylazopyridine. (7) Observation of a rate constant ratio of 22 000 in the rearrangement of these α- and β-isomers, and the proposal of differential barriers for transition states leading to a tricationic intermediate. B. Benzidine rearrangement and cognate studies — (8) Observation of the acid-catalyzed hydroxylation of phenylazopyridine to p-hydroxyphenylazopyridine and the proposal of an SNAr mechanism with formation of an intermediate hydrazo species in the reaction. (9) First study of benzidine type rearrangement-disproportionation of phenylhydrazopyridine in acid media. (10) Proposal of a A [Formula: see text] B [Formula: see text] C [Formula: see text] D type reaction profile for the consecutive hydroxylation[Formula: see text]disproportionation processes of phenylazopyridine in aq H2SO4. (11) Proposal of 10-π and 14π-electron electrocyclic processes in the benzidine type rearrangement-disproportionation of phenylhydrazopyridine. (12) Identification and structural elucidation of a dimer formed from phenylazopyridine as a minor product and proposal of a reaction mechanism. C. Facile acid-catalyzed demethylation via SNAr/A-SE2 mechanisms and studies of tautomerism — (13) Observation of an abnormally facile acid-catalyzed cleavage (demethylation) of 4-methoxyphenylazopyridine via an SNAr mechanism. (14) Observation of two reaction pathways, SNAr and A-SE2, for the consecutive demethylations of 3,4-dimethoxyphenylazopyridine, with rate constant ratio of 7 000:1 favoring the SNAr process. (15) Quantitation of the tautomeric and protonation equilibria of 4-hydroxyphenylazopyridine, produced in (13). D. A new solvent polarity scale, molecular switches, and molecular electronics — (16) Establishment of a π*azo solvent polarity scale based on solvatochromism of a series of azomerocyanine molecules ("Buncel's dye"). (17) Some glimpses are presented of current forays into molecular electronics, as emanating from the above studies: (a) spiropyran (SP) <—> merocyanine (MC) thermo- and photochromic "molecular switch" systems; (b) synthesis and characterization of azo-functionalized star-burst dendrimers with photoswitchable properties and potential applications in optical data storage systems, holographic gratings, and drug delivery systems as host molecules.Key words: Wallach rearrangement, benzidine disproportionation, azoarenes, azoxyarenes, dendrimers, hydrazoarenes, dendrimers, solvatochromism, photochromism, thermochromism, spiropyran-merocyanine molecular switch.

Study of different methods for enhancing the nitrate removal efficiency of a zero-valent metal process

2006 ◽  
Vol 53 (11) ◽  
pp. 81-87 ◽  
Author(s):  
S.F. Cheng ◽  
C.Y. Huang ◽  
J.Y. Liu
Keyword(s):  
Metal Surface ◽  
Removal Efficiency ◽  
Reaction Pathway ◽  
Nitrate Removal ◽  
Optimum Process ◽  
Process Conditions ◽  
Study Results ◽  
Major Reaction ◽  
Acid Wash ◽  
Main Determinants

This study explores the effect of several enhancing methods, namely acid wash pretreatment, ultrasound treatment and addition of nickel catalyst on the nitrate removal efficiency of three zero-valent metals – iron, aluminium and zinc. It is hoped that by learning about the major reaction pathways of nitrate removal with zero-valent metals and the main factors influencing the reactivity of those zero-valent metals, optimum process conditions may be identified. The study results show that direct transfer of electrons is the major reaction pathway. Thus increasing a clean, fresh metal surface and decreasing the thickness of the diffusion layer to accelerate mass transfer are the main determinants of reaction rate. In the absence of a clean, fresh metal surface, the catalytic reaction of nickel becomes the primary removal pathway.

Syntheses of azapolycyclic compounds by aminium radical routes: trapping of the radical intermediates

1978 ◽  
Vol 56 (22) ◽  
pp. 2906-2913 ◽  
Author(s):  
Richard A. Perry ◽  
Robert W. Lockhart ◽  
Masayuki Kitadani ◽  
Yuan L. Chow
Keyword(s):  
Nitrous Acid ◽  
Lone Pair ◽  
Reaction Pathways ◽  
Cleavage Reaction ◽  
Nitrate Esters ◽  
Radical Intermediates ◽  
Radical Trapping ◽  
Primary Products ◽  
Nucleophilic Displacement ◽  
Aziridinium Ion

Photolysis of three alkenyl nitrosamines in the presence of oxygen or bromotrichloromethane resulted in the interception of the intermediate C-radicals by these radical trapping agents and the reaction pathways were cleanly diverted leading to the formation of the nitrate esters or halides with pyrrolidine rings as the primary products. The exo-nitrates in the oxidative photolyses decomposed by secondary ionic pathways; these reactions were hydrolysis, nitrous acid elimination and a cleavage reaction (promoted by a β-amino group), among others. The efficiency of the cleavage reaction is controlled by a stereoelectronic factor that requires the participating bonds and the lone-pair nitrogen orbital be oriented in an antiperiplanar conformation. When such a conformation exists in a rigid or semiflexible framework, cleavage occurs extensively. However, in freely rotating acyclic systems, cleavage does not occur even when the required conformation can be attained. Only halides resistant to intramolecular nucleophilic displacement to form the aziridinium intermediates were isolated in the bromotrichloromethane trapping experiments. Other exo-halides underwent solvolysis via aziridinium ion intermediates.

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