Methyl Radicals in Solid Acetonitrile: Decay or No Decay

Sargent, F. P.; Bailey, Marshall Grant; Gardy, Edward Michael

doi:10.1139/v74-314

Cited by 8 publications

(6 citation statements)

References 5 publications

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“…This provides further support for the view that many of the intermolecular hydrogen atom transfers that have been observed in matrices at low temperatures should be interpreted in terms of quantum-mechanical tunneling.7•8'19'22•23 rather than by invoking any special "matrix effect". 24 3. The rate constants for the isomerization of 1 become virtually independent of the temperature below ca.…”

Section: Discussionmentioning

confidence: 99%

Kinetic applications of electron paramagnetic resonance spectroscopy. 32. Further studies of quantum-mechanical tunneling in the isomerization of sterically hindered aryl radicals

Brunton¹,

Gray²,

Griller³

et al. 1978

J. Am. Chem. Soc.

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Section: Discussionmentioning

confidence: 99%

Kinetic applications of electron paramagnetic resonance spectroscopy. 32. Further studies of quantum-mechanical tunneling in the isomerization of sterically hindered aryl radicals

Brunton¹,

Gray²,

Griller³

et al. 1978

J. Am. Chem. Soc.

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“…Such insights are provided by EPR and optical studies carried out in the 1960s and 1970s on the radical anions produced by irradiation of crystalline alkyl cyanides. − The main results of these studies are summarized in the 1982 review by Williams and Sprague . Irradiated single crystal and polycrystalline samples of frozen alkyl cyanides were found to yield either monomer or dimer radical anions with distinct EPR signatures.…”

Section: Introductionmentioning

confidence: 99%

Electron Localization in Solid Acetonitrile

2002

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Electron localization in the bulk condensed phases of acetonitrile differs drastically from the corresponding processes that take place in water and aliphatic alcohols. In particular, electron capture following the ionization of liquid and solid acetonitrile yields well-defined radical anions in place of the largely structureless solvated and trapped electrons characteristic of irradiated solutions and rigid glasses. This is remarkable given the many similarities that exist not only between the intrinsic properties of these individual solvent molecules, such as polarity, but also in their cooperative capacity to function as solvents. Here, with the aid of detailed experimental and computational studies, we examine on a fundamental level what gives rise to such a sharp contrast in the behavior of these alkyl cyanides as compared to water and alcohols. EPR and optical spectra, and ab initio calculations on the radical anions are used together with diffraction data for the crystal structures to demonstrate that electron attachment to nitrile molecules in the crystalline state results in a significant bending of the linear CCN moiety. Moreover, in the formation of the dimer anions, which only takes place in certain crystalline phases, it is determined that the intermolecular bonding occurs between the cyanide carbons in an antiparallel arrangement. A staggered structure for the dimer anion in R-acetonitrile is then suggested, in which there is a nearly coplanar arrangement with the two bent CCN fragments. The resulting structure accounts for the observed EPR parameters, the position of the UV-vis absorption band, and the trends observed in the vibronic progressions for the four H/D isotopomers. The dimer radical anion in R-acetonitrile retains the same orientation and symmetry as that of the preexisting neutral {CH 3 CN} 2 pairs in this crystal despite the resulting changes in molecular geometry and in the translational coordinates for the cyanide carbons as the two acetonitrile molecules come together. We suggest that dimer anions of nitriles can form only in the phases where such "antiparallel" pairs occur, including liquid systems; otherwise, the electron remains attached to a single molecule, as in β-acetonitrile. Because electron capture by water or alcohol molecules in the condensed phase appears to require larger molecular clusters, the contrast between the behavior of these solvents and acetonitrile is attributable to the relative ease with which acetonitrile molecules in the crystal or solvent can undergo valence-electron attachment via their accessible low-lying π* orbitals.

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“…0.10 ± 0.02 mmol J -1 , 26-28 and the radical cation undergoing ion molecule reactions to form alkoxyl and alkyl radicals. 29 The alkoxyl radicals are oxidizing in nature and because of the relatively lower bond strength of the a-C-H bond of propan-2-ol, a proportion of the radical cation yield gives rise to the ahydroxyprop-2-yl radical giving an overall yield (G-value) of oneelectron reductants in irradiated propan-2-ol of ca. 0.2 mmol J -1 .…”

Section: Radiolysis Of Propan-2-olmentioning

confidence: 99%

Release of nitrite from the antitubercular nitroimidazoledrug PA-824 and analogues upon one-electron reduction in protic, non-aqueous solvent

et al. 2010

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The one-electron reduction chemistry of the antituberculosis drug PA-824, together with a series of closely related compounds, has been investigated in irradiated anaerobic propan-2-ol solution. The protic solvent, of low dielectric constant, was chosen to mimic the environment of a water-restricting active site of a model protein, which is capable of reducing the compounds. Radiolytic reduction of the compounds containing electron donating substituents in the 2-position of the imidazole ring released nitrite, with compounds that are highly active against Mycobacterium tuberculosis exhibiting high yields of nitrite. The release of cytotoxic reactive nitrogen species through a one-electron pathway, by as yet unidentified proteins, may play a role in the activity of this class of compounds against TB. The described radiolytic quantification of nitrite release may have utility as a preliminary screening test for nitroaromatic candidate drugs against the disease.

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Methyl Radicals in Solid Acetonitrile: Decay or No Decay

Cited by 8 publications

References 5 publications

Kinetic applications of electron paramagnetic resonance spectroscopy. 32. Further studies of quantum-mechanical tunneling in the isomerization of sterically hindered aryl radicals

Kinetic applications of electron paramagnetic resonance spectroscopy. 32. Further studies of quantum-mechanical tunneling in the isomerization of sterically hindered aryl radicals

Electron Localization in Solid Acetonitrile

Release of nitrite from the antitubercular nitroimidazoledrug PA-824 and analogues upon one-electron reduction in protic, non-aqueous solvent

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