1991 Fiscal Year Final Research Report Summary
Structure-Stability Relationship of Gaseous Radical Ions
| Project/Area Number |
02640416
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
有機化学一般
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| Research Institution | Okazaki National Research Institutes |
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Principal Investigator |
MASAAKI Mishima Okazaki National Research Institutes, Institute for Molecular Science, Research Associate, 分子科学研究所, 助手 (20037279)
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| Project Period (FY) |
1990 – 1991
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| Keywords | Structure-reactivity Relationship / Electron Affinity / Radical Anion / Ion Cyclotron Resonance / Gaseous Ion-molecule Reaction |
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| Research Abstract |
Electron affinities (EA) of aromatic compounds such as nitrobenzene and benzophenones have been determined by measuring equilibrium constants of electron transfer reactions using a homemade pulsed ion cyclotron resonance spectrometer. Structure-reactivity relationship has been examined for thermodynamic stabilities of radical anions.
The substituent effect on EA of nitrobenzene has been analyzed by means of the LArSR Eq., providing a rho of -19.4 and an r of 0.66. These parameters are very similar to those for gas phase acidities of phenols, suggesting that the mechanism of pi-delocalization of negative charge in a radical anion is close to that of phenoxide. Steric inhibition of resonance effect of the nitro group on EA is found, to be relatively small compared with that in solution, suggesting that the SSSAR(specific substituent solvent assisted resonance)effect also is reduced by steric effect. Electron affinities of 2, 6-dimethyl-4-substituted nitrobenzenes showed the same substituent effect as that of 4-substituted nitrobenzene regardless of reduced stability of the parent radical anion. This may be characteristic nature of SOMO of the nitrobenzene radical anion. On the other hand, the sensitivity of the substituent effect for benzophenone having lower EA than nitrobenzene is found to be reduced by 0.75 compared with that for nitrobenzene. In addition, there is only a crude correlation between EAs of benzonitriles and the corresponding nitrobenzenes. These findings are not consistent with the accepted conclusion that the more stable radical anion has higher response to substituent change and the lower contribution of resonance effect of substituents.
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