2002 Fiscal Year Final Research Report Summary
Complex Formation of Free Radicals and Recombination Reaction of the Complexes
| Project/Area Number |
13640517
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Physical chemistry
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| Research Institution | Japan Women's University |
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Principal Investigator |
OBI Kenichi Japan Women's University, Department of Chemical and Biological Sciences, Professor, 理学部, 教授 (10016090)
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| Project Period (FY) |
2001 – 2002
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| Keywords | benzophenone ketyl radical / complex formation / laser flash / transient absorption / recombination reaction / rate constant |
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| Research Abstract |
In this project, the complex formation of the benzophenone ketyl radical (BPK) with amines and the reconbination rates of radical complexes have been studied with the laser flash photolysis technique. The benzophenone ketyl radicals were formed by the hydrogen atom abstraction reaction of triplet benzophenone from solvent molecules,. The excitation laser used was a 308 nm XeCl excimer laser. To obtain the recombination reaction rate, molar extinction coefficient should be determined. The extinction coefficient of BPK-tri-n propylamine (TPA) complex was obtained to be ε(548 nm) = 4100 M^<-1> cm^<-1> at absorption maximum. Relative recombination rate constants to that of free BPH radical was determined to be 1/2.0 for BPK-triethylamine (TEA) and 1/1.4 for BPK-TPA complexes in cyclohexane using obtained and reported ε values. This result is unexpected because the steric hindrance of TEA is smaller than that of TPA. The reason for this discrepancy may be as follows; 1) difference of strength of hydorogen bonds between BPK and amines, and/or 2) difference of flexibility between TEA and TPA.
To elucidate the effect of solvent viscosity, the recombination rates were measured in benzene. The recombination rate of BPK-TPA complex in benzene is 1.6 time faster than that in cyclohexane. According the theory, the diffusion rate in solution is inversely proportional to viscosity. The ratio of inverse of viscosity of cyclohexane to benzene is 1.46, and shows good coincident with that of the measured values. This result indicates that the recombination proceeds through diffusion control.
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