Gas-phase High Resolution NMR and its Application to Structural Chemistry

气相高分辨率核磁共振及其在结构化学中的应用

• 批准号: 63470006
• 负责人: HIRANO Tsuneo
• 金额: $ 3.2万
• 依托单位: University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (B)
• 财政年份: 1988
• 资助国家: 日本
• 起止时间: 1988 至 1989
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-63470006/
• 关键词: gas-phase nmr; structural chemistry; unperturbed state; Gibbs free energy; 1,2-difluoroethane; gauche effect; conformational energy; ab initio; 気相高分解能NMR; NMR; 配座エネルギー; 1、2-ジフロロエタン

Low pressure (0.01 - 0.5 atm) Gas-phase high-resolution NMR method is a useful tool for the structural study of unperturbed states, i.e. states free from solvent and intermolecular interactions. Their data can directly be compared with the predictions from quantum chemical and molecular mechanics calculations since these methods also calculate for a molecule in an isolated state.In this study, we extended our novel method for the ^1H NMR to ^<19>F and ^<13>C NMR, and made some applications to the structural problems.1) We have succeeded in developing new observation method for ^<19>F nucleus NMR, and was able to obtain NMR spectra of very high resolution.2) Applying the variable temperature ^1H and ^<19>F gas-phase NMR methods to the investigation of "gauche-effect" in 1,2-difluoroethane, we determined enthalpy and entropy differences between gauche and trans conformers in the unperturbed states. The Gibbs free energy difference thus determined, DELTAG(G-T), is -0.81 kcal/mol, which is in good agreement with the value -0.85 kcal/mol from MP3/6-311++G^<**> ab initio calculations. The 1-4 through bond interaction between H and F atoms was found to play the most important role in the gauche-effect.3)Taking methanol and dimethyl ether as examples, we succeeded in obtaining a well-resolved ^<13>C low pressure gas-phase NMR spectra at 270 MHz with 10 mm sample tube. Method of observation should further be improved for general applications, but it could become a useful tool for the structural chemistry in the unperturbed state.

低压（0.01 - 0.5 atm）气相高分辨NMR方法是研究未扰动态（即不含溶剂和分子间相互作用的状态）结构的有用工具。本研究中，我们将我们的新方法推广到~ 1H NMR和~ 1F <19>~ 1C <13>NMR，并在结构问题上作了一些应用：1）我们成功地发展了~ 1F核NMR的新观测方法<19>，并能获得很高分辨率的NMR谱; 2）将变温~ 1H和~ <19>1F气相NMR方法应用于1，2-二氟乙烷的“gauche效应”研究，我们确定了在未扰动状态下的偏位和反式构象之间的焓差和熵差。由此测定的吉布斯自由能差DELTAG（G-T）为-0.81 kcal/mol，这与来自MP3/6-311++G^** 从头计算的值-0.85 kcal/mol非常一致。3）以甲醇和二甲醚为例，<13>采用10 mm的样品管，在270 MHz下成功地获得了高分辨的~ 1C低压气相NMR谱。对于一般的应用，观测方法还需要进一步改进，但它可以成为非微扰态结构化学的有用工具。

项目成果

Tsuneo Hirano,Shinji Nonoyama: "Conformational Energies of 1,2-Difluoroethane by ‘H and“F Gas-phase Highresolution NMR" J.Phys.Chem.

Tsuneo Hirano、Shinji Nonoyama：“通过‘H’和‘F’气相高分辨率 NMR 测定 1,2-二氟乙烷的构象能”J.Phys.Chem。

Tsuneo HIRONO: "Gauche Effect In Conformational Energies of Linear Molecules:Ab Initio Molecular Orbital Calculations" PACIFICHEN'89,講演要旨集. INFO. 186 (1989)

Tsuneo HIRONO：“线性分子构象能量的高什效应：从头算分子轨道计算”PACIFICHEN89，讲座摘要 186 (1989)。

Tsuneo Hirano,Shinji Nonoyama: "Conformational Energies of 1,2-Difluoroethane by 'H and "F Gas-phase Highresolution NMR" J.Phys.Chem.(投稿準備中).

Tsuneo Hirano、Shinji Nonoyama：“通过 H 和“F 气相高分辨率 NMR 测定 1,2-二氟乙烷的构象能量”J.Phys.Chem.（准备提交）。

Tsuneo Hirano, Shinji Nonoyama: "Conformational Energies of 1,2-Difluoroethane by 'H and "F Gas-phase Highresolution NMR" J. Phys. Chem.

Tsuneo Hirano、Shinji Nonoyama：“H 和 F 气相高分辨率 NMR 测定 1,2-二氟乙烷的构象能量”J. Phys. Chem。

Tsuneo,Hirano Takashi,Miyajima: J.Phys.Chem.

Tsuneo，平野隆，宫岛：J.Phys.Chem。