1987 Fiscal Year Final Research Report Summary
Study of Transition-State Structures of Accelerated Reactions
| Project/Area Number |
61470024
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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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 | Shiga University of Medical Science |
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Principal Investigator |
ANDO Takashi Shiga University of Medical Science, Professor, 医学部, 教授 (70029867)
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| Co-Investigator(Kenkyū-buntansha) |
FUJITA Mitsue Shiga University of Medical Science, Research Assistant, 医学部, 教務職員 (40175576)
KIMURA Takahide Shiga University of Medical Science, Research Associate, 医学部, 助手 (70167378)
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| Project Period (FY) |
1986 – 1987
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| Keywords | transition-state structure / kinetic isotope effect / aliphatic nucleophilic substitution / inorganic solid-supported reagent / omega phase / ポテンシアルエネルギー面 |
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| Research Abstract |
Transition-state structures of aliphatic nucleophilic substitutions accelerated by electronic effect, solvent effect, phase-transfer catalysts, and neighboring group participation were elucidated by means of kinetic isotope effects of secondary deuterium, primary carbon-13 and -14, and nitrogen-15. Variation in the transition states of the Menschutkin-type alkyl transfer reactions by electronic perturbation of substituents introduced on the nucleophile, leaving group, and alkyl substrate were successfully interpreted by the use of the More O'Ferralltype potential energy surface diagram. Benzyl transfer reaction has more flexible transition state than methyl transfer, presumably because of the greater polarizability of the phenyl group compared with that of hydrogen. Although hydration of nucleophiles in nonpolar solvents with a small number of water molecules slows down the rate of reactions catalyzed by phase-transfer catalysts to a great extent, a-deuterium kinetic isotope effects sh
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owed no indication of considerable changes in the transition-state structure. Acceleration by solvent change also has only subtle effect on the transition-state structure and difficult to interpret. Intramolecular nucleophilic substitutions by neighboring group are important in determining the rate of reactions. Variation in the transition-state structure of these reactions is interpreted in a similar manner as that used for intermolecular nucleophilic substitutions. Acceleration caused by inorganic solid supports in organic solvents becomes maximum by the addition of a trace amount of water. This is attributed to the formation of the "Omega phase", a very polar phase on the inorganic solid, in which nucleophiles are active because of the release from the crystal lattice and insufficient solvation. Taking advantage of this active state, efficient catalytic and noncatalytic reactions by solid base, nucleophilic substitutions, and electrohpilic additions were developed. Selectivity could also be altered in these interfacial reactions. Less
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Research Products
(12 results)
