2001 Fiscal Year Final Research Report Summary
Super-fine Conformational Analysis of Organic Molecules based on the Temperature Variable Rare Gas Matrix Isolation Method
| Project/Area Number |
12640520
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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 | Hiroshima University |
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Principal Investigator |
YOSHIDA Hiroshi Hiroshima Univ., Graduate School of Science, Associate Professor, 大学院・理学研究科, 助教授 (60222395)
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| Project Period (FY) |
2000 – 2001
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| Keywords | Matrix-isolation Method / Infrared Spectroscopy / Density Functional Theory / Conformational Analysis / Vibrational Analysis |
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| Research Abstract |
Conformational Stabilization of 1-Methoxy-2-(methylthio)ethane by an Intramolecular CH…O Attractive Interaction : Temperature-variable Matrix-isolation Infrared Spectroscopic Study with Density Functional Theory. Intramolecular 1,5-CH…O interaction in 1-methoxy-2-(methylthio)ethane have been studied by matrix-isolation infrared spectroscopy and density functional theory. In an argon matrix, the conformer with trans-trans-gauche^±(TTG) around the CH3O-CH2-CH2-SCH3 bonds is the most stable and the conformer with TGG' is the second most stable. The energy difference between the TGG' conformer and the TTG conformer is estimated at only 0.69±0.10 kJ mo^<-1> by analysing the area intensity ratio of the spectra measured with temperature-variable matrix-isolation infrared spectroscopy. The Conformational stability and energy difference calculated by density functional theory are consistent with these experimental results.
A New Approach to Vibrational Analysis of Large Molecules by Density Functional Theory : Wavenumber-Linear Scaling Method. Normal vibration calculations were performed on 164 basic organic and inorganic compounds by the density functional method of B3LYP/6-311+G** using the wavenumber-linear scaling (WLS) method, in which essentially only one parameter is involved for the whole wavenumber region. The average deviation of the WLS-scaled calculated wavenumbers from the observed wavenumbers for a total of 1223 normal modes was 3.4%. The effect of vibrational anharmonicity on the observed wavenumbers was examined on the basis of the calculated wavenumbers for 224 diatomic molecules and ions in comparison with their experimental harmonic wavenumbers. The results indicate that the more deviations upward of the unsealed calculated wavenumbers from the observed values at higher wavenumbers are attributed almost exclusively to the neglect of vibrational anharmonicity in the calculated wavenumbers.
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