Radiolysis of hydrocarbons: Chloroform in liquid hexane

Tuấn, Nguyễn Quốc; Gäumann, Tino

doi:10.1016/0146-5724(77)90028-0

Cited by 9 publications

(3 citation statements)

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“…The only reported rate constant for the abstraction of a hydrogen atom from chloroform by an n-alkyl radical comes from the early work of Tuan and Gaumann who studied the radiolysis of liquid binary mixtures of n-hexane and chloroform. 45 This study produced a rate constant, k H , for the HAT from chloroform to n-hexyl of 4.8 × 10 3 M −1 s −1 at −10 °C. Using the ethyl radical as a model for the n-hexyl system, our calculations predict a 9.5-fold increase in rate going from −10 to 60 °C (see Supporting Information).…”

Section: ■ Resultsmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

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Chloroform as a Hydrogen Atom Donor in Barton Reductive Decarboxylation Reactions

Zheng

Meana-Pañeda

et al. 2013

J. Org. Chem.

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The utility of chloroform as both a solvent and a hydrogen atom donor in Barton reductive decarboxylation of a range of carboxylic acids was recently demonstrated (Ko, E. J. et al. Org. Lett. 2011, 13, 1944). In the present work, a combination of electronic structure calculations, direct dynamics calculations, and experimental studies was carried out to investigate how chloroform acts as a hydrogen atom donor in Barton reductive decarboxylations and to determine the scope of this process. The results from this study show that hydrogen atom transfer from chloroform occurs directly under kinetic control and is aided by a combination of polar effects and quantum mechanical tunneling. Chloroform acts as an effective hydrogen atom donor for primary, secondary, and tertiary alkyl radicals, although significant chlorination was also observed with unstrained tertiary carboxylic acids.

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Section: ■ Resultsmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Chloroform as a Hydrogen Atom Donor in Barton Reductive Decarboxylation Reactions

Zheng

Meana-Pañeda

et al. 2013

J. Org. Chem.

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“…The first involves direct H-transfer from chloroform to the alkyl radical ( 6 ), thus furnishing the observed reduction product ( 2 ) and the trichloromethyl radical ( 14 ), which then propagates the radical chain reaction through attack at the sulfur terminus of the thiohydroxamic ester ( 3 ), thereby furnishing the pyridyl sulfide coproduct ( 15 ) and a new alkyl radical 6 (path A). Available H-transfer rate constants ( k H ) for chloroform from the work of Tuan and Gäumann through the reaction of hexyl radicals with chloroform provided k H of 4.8 × 10 3 M −1 s −1 at −10 °C, whereas the k H for the adamantyl and tert -butyl radicals at 25 °C were determined to be 2.9 × 10 3 M −1 s −1 and 2.54 × 10 2 M −1 s −1 , respectively. This data effectively places an upper limit for the k H for chloroform with alkyl radicals at ca .…”

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confidence: 99%

Reducing the Cost, Smell, and Toxicity of the Barton Reductive Decarboxylation: Chloroform as the Hydrogen Atom Source

Savage

Williams

et al. 2011

Org. Lett.

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Polymer Degradation and Stabilization

Nguyen¹

2005

Handbook of Polymer Reaction Engineering

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IntroductionMost synthetic plastics and natural polymers are principally constituted of the elements C, H, N, and O, all of which are primary components of organic molecules. As with smaller organic molecules, these atoms are attached by relatively weak covalent bonds that are susceptible to chemical attack, particularly to oxidative degradation. During their potential lifetime, engineering plastics are exposed to diverse environmental factors which can act alone or in combination to adversely affect the initial material properties. These changes generally occur over several years, but can be accelerated or retarded in the presence of internal and external elements temperature, and temperature variations. Environmental factors that contribute to degradation include mechanical stresses, temperature variations, humidity, sunlight, oxygen, atmospheric pollutants, and microbial enzymes. Depending on the structural level at which material changes occur, it is usual to distinguish between physical, physicochemical, and chemical degradation.Physical degradation, commonly known as physical aging, results from changes in the thermodynamic state of the system (temperature, pressure, molar volume) during the daily use of the material. During processing, chains may be oriented and the sample inhomogeneously cooled, resulting in internal stress. With time, the chains have the opportunity to relax from their nonequilibrium conformations to a state of lower free energy. Partly immiscible blends, for instance, can remain in a homogeneous metastable state for an extended period of time. The presence of stress or heat can accelerate the phase separation process. The resultant changes in orientation, free volume, internal stress, crystalline content, and

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Radiolysis of hydrocarbons: Chloroform in liquid hexane

Cited by 9 publications

References 19 publications

Chloroform as a Hydrogen Atom Donor in Barton Reductive Decarboxylation Reactions

Chloroform as a Hydrogen Atom Donor in Barton Reductive Decarboxylation Reactions

Reducing the Cost, Smell, and Toxicity of the Barton Reductive Decarboxylation: Chloroform as the Hydrogen Atom Source

Polymer Degradation and Stabilization

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