2004 Fiscal Year Final Research Report Summary
A quantum chemical approach to the study of a novel reaction path and its control in the supercritical water
| Project/Area Number |
15360422
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Reaction engineering/Process system
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| Research Institution | Osaka University |
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Principal Investigator |
NITTA Tomoshige Osaka University, Graduate School of Engineering Science, Professor, 大学院・基礎工学研究科, 教授 (00029480)
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| Co-Investigator(Kenkyū-buntansha) |
TAKAHASHI Hideaki Osaka University, Graduate School of Engineering Science, Associate Professor, 大学院・基礎工学研究科, 助教授 (10291436)
FURUKAWA Shin-ichi Osaka University, Graduate School of Engineering Science, Research Associate, 大学院・基礎工学研究科, 助手 (50333448)
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| Project Period (FY) |
2003 – 2004
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| Keywords | Density functional theory / Real-space grid / QM / MM method / Free energy / Energy representation / QM / MM-ER |
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| Research Abstract |
The results obtained by present work can be summarized by the following two subjects. One is that a novel methodology (QM/MM-ER) has been developed to compute the free energy change associated with a chemical reaction in a condensed phase. The other is that a novel reaction pathway has been explored by means of the QM/MM-ER simulations. It has been suggested that the proton transfers along the hydrogen bonds of water molecules promote the dehyderation of butanediol in hot water. The details of the results have been itemized as follows.
(1)Quantum chemical approach to the free energy calculation in condensed phase
In order to compute the free energy change associated with a chemical reaction in aqueous solution, we have combined the quantum mechanical/molecular mechanical approach with the theory of energy representation. Within the theory of the energy representation, the solvation free energy of a solute is described in terms of the distribution functions of the solute-solvent interaction energy instead of the spatial distribution function used in the conventional theory of solution. Since the method of the energy representation does not need the concept of the interaction site, the combination with the quantum chemical treatment is straightforward.
(2)Quantum chemical calculation for the dehydration reaction of alcohol
Quantum chemical calculations have revealed that butanediol forms a biradical electronic structure at the transition state (TS) of the proton transferring reaction. The activation energy is extremely high (〜70 kcal/mol) in the gaseous phase, however, it reduces to 〜50 kcal/mol in hot water. The electronic state of the TS forms a zwitterionic structure in the polar solvent, which leads to the stabilization of the TS as compared to the reactant. Thus it has been suggested that the proton-transfer mechanism catalyzes the dehydration reaction of alcohol in hot water.
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Research Products
(8 results)
