| Project/Area Number |
05453032
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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 |
Organic chemistry
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
FUJIO Mizue Kyushu Univ.Inst.Fund.Res.Org.Chem., Associate Professor, 有機化学基礎研究センター, 助教授 (10029887)
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| Project Period (FY) |
1993 – 1994
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| Project Status |
Completed (Fiscal Year 1994)
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| Budget Amount *help |
¥7,500,000 (Direct Cost: ¥7,500,000)
Fiscal Year 1994: ¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 1993: ¥5,800,000 (Direct Cost: ¥5,800,000)
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| Keywords | Nucleophilic Displacement / Menschutkin Reaction / Duality of S_N1-S_N2 / Solvolysis Mechanism / Ion-pair Return / Ion-pair Intermediate / O-18 Scrambling / C-13 NMR / 0-18スクランブリング / S_N1S_N2機構二次性 / 溶媒効果 |
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| Research Abstract |
The ^<18>O-scrambling within starting sulfonate during the Menschutkin reaction of pmethylbenzyl-1-^<13>C tosylate-S^<18>O_2 with N,N-dimethylanilines which is typical S_N2 displacement reaction, was determined in MeCN at 35ﾟC by ^<13>C-NMR spectroscopy utilizing the split ^<13>C-NMR signals of alkoxy carbon induced by ^<18>O/^<16>O isotopic substitution. For the ^<13>C peak of benzyl carbon of starting tosylates, a new ^<13>C peak caused by ^<18>O isotope effect gradually grew up with time. This finding of unambiguous ^<18>O-scrambling in starting tosylate demonstrated the existence of the carbocationic intermedates in the typical S_N2 reaction in MeCN.The rate of product formation (k_t) and the decreasing rate of unreacted tosylate (k_i) of this reaction are determined with various DMA concentrations. The difference between k_t and k_i values is unchanged with DMA conentrations, irrespective of the nucleophilicity of DMA.This k_i-k_t value is in accordance with the rate of ^<18>O-scrambling of p-methylbenzyl tosylate in the absence of DMA.This result gives the important evidence that benzyl tosylate ionizes independently via S_N1 mechanism irrespective of concurrent S_N2 mechansim. The subsequent nucleophilic attack in this unimolecular ionization process is so slow that the return from the ion-pair intermediate can not be removed effectively. It is concluded that the S_N1 and S_N2 processes are quite distinct that these results afford no evidence for a single mechanism intermediate between S_N1 and S_N2 in this reaction.
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