| Project/Area Number |
12650810
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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 |
工業物理化学
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
KITAGAWA Toshikazu Kyoto University, Institute for Chemical Research, Associate Professor, 化学研究所, 助教授 (20183791)
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| Co-Investigator(Kenkyū-buntansha) |
TAKEUCHI Ken'ichi Kyoto University, Graduate School of Engineerikng, Professor, 大学院・化学研究科, 教授 (50026358)
KOMATSU Koichi Kyoto University, Institute for Chemical Research, Professor, 化学研究所, 教授 (70026243)
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| Project Period (FY) |
2000 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2001: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2000: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Keywords | fullerene / carbocation / alkylation / electrophilic addition / fullerenol / ^<13>C NMR / 分子内配位 |
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| Research Abstract |
We found that fullerene C_<60> undergoes electrophilic addition when treated with a large excess of AlCl_3 in chloroalkanes (RCl), giving adducts RC_<60>-Cl in good yields. The intermediate, alkylfullerenyl cations (RC_<60>^+), could be generated as long-likved ions by dissolving fullerenols (RC_<60>OH) in strong acids such as CF_3SO_3H and H_2SO_4. These cations were observed by NMR and vis/NIR spectra as long-lived species. The ^<13>C NMR spectra indicated that the positive charge is located mainly on C-2, and the structure has C_s symmetry. The chemical shift of the cationic center (175-180 ppm) suggested a weak coordination of chlorine atom(s) in the group R to the cationic center.
Cations RC_<60>^+ could be also generated in situ by the abstraction of a chloride ion from chlorides RC_<60-> Cl with AlCl_3. When the reactions were carried out in anisole, nucleophilic addition of a solvent molecule to RC_<60>^+ occurred, giving the corresponding adducts RC_<60>-C_6H_4OCH_3-p. The chloride ion can be also abstracted by AgBF_4. With this reagent the reaction could be carried out in alcohols (R'OH), giving the corresponding ethers RC_<60>-OR' in good yiels.
Chlorides RC_<60>-Cl (R=chloroalkyl) were found to undergo solvolysis in anisole-trifluoroethanol mixed solvent (1:9 v/v) to give S_N1 reaction products, RC_<60>-Y(Y=p-anisyl and trifluoroethoxy). The free energies of activation (24-25 kcal/mol at 25℃) were only slightly lower than that for the tert-butyl chloride, indicating that cations RC_<60>^+ have stabilities close to that of the tert-butyl cation.
The pK_R^+ values of cations RC_<60>^+ were also determined from the equilibrium constants for the ionization of the corresponding fullerenols. The obtained values are comparable to the pK_R+ of the tert-butyl cation. Thsi result also support the similarity in stability between RC_<60>^+ and the tert-butyl cation.
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