2007 Fiscal Year Final Research Report Summary
Combined experimental and Computational Study on New Concept of Dynamics-Driven Organic Reaction and Path Bifurcation
| Project/Area Number |
18550047
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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 |
Organic chemistry
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| Research Institution | Rikkyo University |
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Principal Investigator |
YAMATAKA Hiroshi Rikkyo University, Department of Chemistry, Professor (60029907)
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| Project Period (FY) |
2006 – 2007
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| Keywords | Beckmann reaction / Molecular dynamics simulations / Organic reaction mechanism / Transition state / Dynamics-driven reaction / Pth bifurcation / Kinetics / Nucleophilic substitution |
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| Research Abstract |
Full quantum molecular dynamic(MD) simulations were carried out for the Beckmann reactions of substituted benzyl methyl ketone oximes and α-phenylethyl methyl ketoximes in the gas phase. The simulations revealed that reaction path bifurcation occurs for borderline substrates, where the reaction product changes from fragmentation to rearrangement with the change of substituent. The bifurcation ratios were found to have correlation with the amount of energy initially given to the reacting system. Physical organic experiment on the substituent effects on rates and product distribution suggests the existence of path bifurcation in these reaction systems.
The hydrolysis reaction of methyl diazonium ion(CH3-N2+) was examined by means of home-made MD simulation application based on recently developed fragment molecular orbital(FMO)-MD method, which allows one to calculate solution dynamics in a full quantum fashion. The simulations were carried out by using a water droplet model consisting with 156 water molecules surrounding the substrate(CH3-N2+) located in the center of the gravity of the system. Under certain reaction conditions, the simulations succeeded to reveal how the reaction takes place and how the atoms in the reaction molecules and solvents behave during the reaction from the reactant state to the product state at the molecular level. The hydrolysis of CH3-N2+ proceeds via the SN2 mechanism since the methyl cation that would form via the C-N cleavage is too unstable to exist in nucleophilic solvent like water. The simulations showed that CH3-N2+ initial interacts with one of the water molecules in its C-H bond, and then H2O interacts with CH3 moiety displacing the N2 leaving group. The O-C-N angle never reached 180°as is written in the textbook. Variable synchronicity was observed for the O-C bond formation and the C-N bond cleavage, showing diversity in chemical reactions in solution.
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Research Products
(59 results)
