在气相中通过红外光谱学监测的纳夫托尔合
1Department of Organic Chemistry, Charles University in Prague, Hlavova 8, 12843 Prague 2, Czech Republic. roithova@natur.cuni.cz
Journal of the American Chemical Society
|December 4, 2009
概括
铜 (II) 介导的醇合发生在气相双核集群中. 辐射触发了C-C合,由-醇分体化驱动,以外热方式形成双.
科学领域:
- 有机金属化学 有机金属化学
- 频谱学是一种光谱学.
- 计算化学计算化学
背景情况:
- 铜催化合反应在有机合成中至关重要.
- 了解分子层面的反应机制对于催化剂设计至关重要.
- 气相研究为反应途径提供了独特的见解,没有溶剂效应.
研究的目的:
- 为了阐明铜(II) 介导的醇合的反应机制.
- 调查TMEDA (N,N,N',N'-四甲基乙二胺) 在合过程中的作用.
- 为了描述气相中涉及的中间物种.
主要方法:
- 红外多光子解离 (IRMPD) 光谱法用于研究孤立的双核星团.
- 用密度函数理论 (DFT) 的计算来建模反应路径和能量.
- 实现了气相隔离和反应中间体的表征.
主要成果:
- 合反应通过特设形成的双核集群进行:[(1-H) ((2) Cu ((2) Cl (((TMEDA) ((2))) ((+).
- IRMPD的光谱证实了集群中未结合的甲酸盐子单元的存在.
- 辐射被确定为C-C合反应的触发因素.
- 最初产品的醇-醇分体化驱动了C-C合,二醇形成是外热 (-0.61 eV).
- 类似的C-O和O-O合被发现是内热的.
结论:
- 该研究揭示了一种真正的气相铜介导纳醇合机制.
- 双核铜集群和随后的辐射是启动C-C键形成的关键.
- 基托-醇复合的热力学优势决定了C-C合路径,而不是C-O或O-O合.
相关概念视频
01:27¹H NMR: Long-Range Coupling
The coupling interactions of nuclei across four or more bonds are usually weak, with J values less than 1 Hz. While these are usually not observed in spectra, the presence of multiple bonds along the coupling pathway can result in observable long-range coupling.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene π orbitals.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene π orbitals.
01:32UV–Vis Spectroscopy of Conjugated Systems
Organic compounds with conjugated double bonds show strong absorption features in the UV–visible region of the electromagnetic spectrum attributed to π → π* electronic excitations. Generally, a UV–vis absorption spectrum is recorded as a plot of absorbance vs wavelength. The wavelength of maximum absorbance, which manifests as a peak in the absorption spectrum, is denoted as λmax.
One of the factors influencing λmax is the extent of conjugation in the...
One of the factors influencing λmax is the extent of conjugation in the...
01:29IR and UV–Vis Spectroscopy of Aldehydes and Ketones
Infrared spectroscopy, also known as vibrational spectroscopy, is mainly used to determine the types of bonds and functional groups in molecules. In aldehydes and ketones, the carbonyl (C=O) bond shows an absorption around 1710 cm-1. The C=O bond vibration of an aldehyde occurs at lower frequencies than that of a ketone. In addition to the C=O absorption in an aldehyde, the aldehydic C–H bond also gives two peaks in the 2700–2800 cm-1 range. This absorption, coupled with the C=O stretching, is...
01:04¹³C NMR: ¹H–¹³C Decoupling
The probability of having two carbon-13 atoms next to each other is negligible because of the low natural abundance of carbon-13. Consequently, peak splitting due to carbon-carbon spin-spin coupling is not observed in spectra. However, protons up to three sigma bonds away split the carbon signal according to the n+1 rule, resulting in complicated spectra.
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
01:28IR and UV–Vis Spectroscopy of Carboxylic Acids
In IR spectroscopy of carboxylic acids, the C=O bond shows a characteristic band between 1710 and 1760 cm⁻¹, and the O–H bond exhibits a broad band between 2500 and 3300 cm⁻¹.
However, the stretching absorptions for the C=O bond vary depending on the structure of carboxylic acids. The C=O bond of the free carboxylic acids shows a higher stretching frequency, 1760 cm−1, while H-bonded carboxylic acids (dimers) exhibit stretching absorptions at a lower frequency, 1710 cm−1. The C=O bond of the...
However, the stretching absorptions for the C=O bond vary depending on the structure of carboxylic acids. The C=O bond of the free carboxylic acids shows a higher stretching frequency, 1760 cm−1, while H-bonded carboxylic acids (dimers) exhibit stretching absorptions at a lower frequency, 1710 cm−1. The C=O bond of the...
01:13¹H NMR: Complex Splitting
A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.