|Budget Amount *help
¥3,300,000 (Direct Cost : ¥3,300,000)
Fiscal Year 1999 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1998 : ¥2,800,000 (Direct Cost : ¥2,800,000)
Density Functional Study on 1,2-Dimethoxyethane in Aqueous Solution. Conformational behavior of 1,2-dimethoxyethane (DME) in aqueous solution has been attracted in the field of experimental and theoretical structural chemistry for a long time. The conformational stability of DME is known to be strongly affected by solvent environment. In the present study, we have observed the Raman spectra of DME in aqueous solution at various concentrations and have calculated the conformational energies by density functional theory (DFT) via Tomasi's polarizable continuum model (PCM) to understand the conformational stabilization mechanism of DME in aqueous solution. In the gas phase, the TTT conformer is the most stable and the TGG' conformer, as stabilized by an intramolecular 1,5-CH・・・O interaction, is the second. The PCM ealculations show that in aqueous solution the TGT conformer is the most stable and the TGG conformer is the second. The TGG conformer is greatly stabilized in aqueous solution
because of the dipole moment of this conformer which is much larger than that of the other conformers. The theoretical results are in excellent agreement with the Raman spectroscopic observations. The present study has indicated that the dielectric property of aqueous environment strongly affects the conformational stabilization of DME.
Density Functional Studies on Computational Accuracy in Normal Coordinate Analysis for Basic Molecules. Recently, density functional theory has rapidly developed and has shown that it calculates accurate chemical properties in a practical time. For the purpose of examining calculation accuracy in normal coordinate analysis using the density functional method, vibrational calculations were carried out using fundamental molecular observation wavenumbers which were reported in "Tables of Molecular Vibrational Frequencies" (T. Shimanouchi, 1972). The calculated wavenumbers by B3LYP using large basis sets are in good agreement with the observed wavenumbers at the accuracy of about 5%. As for the compounds involving halogens, calculated wavenumbers tend to deviate considerably to the lower wavenumber side.
平成10年度の研究において,振動解析を行ううえでは,特にBecke 3 Typeの密度汎関数法が非常によい結果を与えることを示した。平成11年度では、さらに多数の基本的な化合物の実測振動数を用いることにより,その基準振動解析における計算精度について系統的研究を行った。基準振動計算は,島内によるデータ集に掲載されている約200種類の基本的な化合物を対象としてB3LYP/6-311+G^<**>レベルで行った。いくつかの化合物では,低波数領域において計算値が実測値に対して大きくずれる場合もあるが,一般的には実測値に対し5%程度の精度で一致した。スケール因子は波数値が大きいモードほど小さな値となり,実測波数値との間になんらかの直線関係がある様子がみられた。 Less