相关实验视频
Updated: Jul 8, 2026

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Photoelectron Imaging of Anions Illustrated by 310 Nm Detachment of F−
Published on: July 27, 2018
通过ClH2-和ClD2-光电子成像探测到的Cl + H2反应中的非adiabatic相互作用
Etienne Garand1, Jia Zhou, David E Manolopoulos
1Department of Chemistry, University of California, Berkeley, CA 94720, USA.
概括
这项研究使用慢电子速度图像绘制 (SEVI) 调查了Cl + H2反应,发现了轻微的非adiabatic效应. 这些发现验证了化学动力学中电子和核合的理论处理.
科学领域:
- 化学动力学 化学动力学
- 量子化学是一种量子化学.
- 分子光谱学 分子光谱学
背景情况:
- 在理解电子和核合时,Cl + H2反应是一个挑战.
- 非adiabatic过渡对于 Cl 激发的旋转轨道状态与 H2 的反应性至关重要.
研究的目的:
- 探测Cl + H2反应潜在能量表面的反应物谷.
- 为了研究非adiabatic合在Cl + H2反应动态中的作用.
主要方法:
- 使用慢电子速度图像成像 (SEVI) 谱法获得了ClH2-和ClD2-的光谱.
- 实验频谱与理论模拟进行了比较,包括和排除非adiabatic合.
主要成果:
- SEVI光谱显示了Cl.H2.2的低频曲和拉伸模式的进展.
- 包括Cl旋转轨道状态之间的非adiabatic合,改善了模拟和实验数据之间的一致性.
- 发现非抗性影响很小,但显著.
结论:
- 在Cl+H2反应中,对非adiabatic效应的理论处理得到了验证.
- 在Cl+H2反应的动力学中,非辅助作用的作用很小.
- SEVI光谱是一种强大的工具,用于探测反应谷中的反应动态.
相关概念视频
Photochemical Electrocyclic Reactions: Stereochemistry
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
Cycloaddition Reactions: MO Requirements for Photochemical Activation
Some cycloaddition reactions are activated by heat, while others are initiated by light. For example, a [2 + 2] cycloaddition between two ethylene molecules occurs only in the presence of light. It is photochemically allowed but thermally forbidden.
Electrophilic Addition of HX to 1,3-Butadiene: Thermodynamic vs Kinetic Control
The addition of a hydrogen halide to 1,3-butadiene gives a mixture of 1,2- and 1,4-adducts. Since more substituted alkenes are more stable, the 1,4-adduct is expected to be the major product. However, the product distribution is strongly influenced by temperature; low temperature favors the 1,2-adduct, whereas the 1,4-adduct is predominant at high temperature.
Electrophilic 1,2- and 1,4-Addition of HX to 1,3-Butadiene
The electrophilic addition of hydrogen halides such as HBr to alkenes and nonconjugated dienes gives a single product as per Markovnikov’s rule.
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
The Diels–Alder reaction is an example of a thermal pericyclic reaction between a conjugated diene and an alkene or alkyne, commonly referred to as a dienophile. The reaction involves a concerted movement of six π electrons, four from the diene and two from the dienophile, forming an unsaturated six-membered ring. As a result, these reactions are classified as [4+2] cycloadditions.
Hess's Law
There are two ways to determine the amount of heat involved in a chemical change: measure it experimentally, or calculate it from other experimentally determined enthalpy changes. Some reactions are difficult, if not impossible, to investigate and make accurate measurements for experimentally. And even when a reaction is not hard to perform or measure, it is convenient to be able to determine the heat involved in a reaction without having to perform an experiment.

