在酸的光解离中形成记忆
Leonid Khriachtchev1, Ermelinda Macoas, Mika Pettersson
1Laboratory of Physical Chemistry, P.O. Box 55, FIN-00014 University of Helsinki, Finland. Leonid.Khriachtchev@Helsinki.Fi
Journal of the American Chemical Society
|September 13, 2002
概括
不同形式的酸 (HCOOH) 产生不同的光解离产物. 这项研究表明,红外线可以通过选择性地准分子对象来控制化学反应.
科学领域:
- 摄影化学的使用.
- 分子光谱学 分子光谱学
- 化学物理 化学物理
背景情况:
- 酸 (HCOOH) 存在于变态和 cis 变态.
- 了解符合特异性的反应对于化学控制至关重要.
- 光解离是分子化学中的一个关键过程.
研究的目的:
- 为了研究酸和酸酸的光解离路径.
- 为了确定在光解离过程中是否保留了形状记忆.
- 探索化学反应的光学控制的潜力.
主要方法:
- 在固体中进行矩阵隔离光谱.
- 193纳米紫外线光解离. 193纳米紫外线光解离.
- 对产品形成 (H2O + CO和H2 + CO2) 的分析.
主要成果:
- 转化HCOOH主要是H2O + CO的形式.
- 在Cis-HCOOH中,主要是H2 + CO2的形式.
- 在合规者之间观察到产品分支比率的显著差异 (>10x).
- 发现了对形态记忆的证据,表明在过渡状态之前的最小扭曲随机化.
结论:
- 选择性光解离酸对象的可实现.
- 形态记忆在确定光解离产物方面发挥着作用.
- 窄带红外辐射可以用来促进异构和指导化学反应.
- 这些发现支持光学控制化学反应的概念.
相关概念视频
Weak Acid Solutions
Few compounds act as strong acids. A far greater number of compounds behave as weak acids and only partially react with water, leaving a large majority of dissolved molecules in their original form and generating a relatively small amount of hydronium ions. Weak acids are commonly encountered in nature, being the substances partly responsible for the tangy taste of citrus fruits, the stinging sensation of insect bites, and the unpleasant smells associated with body odor. A familiar example of a...
Polyprotic Acids
Acids are classified by the number of protons per molecule that they can give up in a reaction. Acids such as HCl, HNO3, and HCN that contain one ionizable hydrogen atom in each molecule are called monoprotic acids. Their reactions with water are:
Acid Strength and Molecular Structure
Binary Acids and Bases
In the absence of any leveling effect, the acid strength of binary compounds of hydrogen with nonmetals (A) increases as the H-A bond strength decreases down a group in the periodic table. For group 17, the order of increasing acidity is HF < HCl < HBr < HI. Likewise, for group 16, the order of increasing acid strength is H2O < H2S < H2Se < H2Te. Across a row in the periodic table, the acid strength of binary hydrogen compounds increases with increasing...
In the absence of any leveling effect, the acid strength of binary compounds of hydrogen with nonmetals (A) increases as the H-A bond strength decreases down a group in the periodic table. For group 17, the order of increasing acidity is HF < HCl < HBr < HI. Likewise, for group 16, the order of increasing acid strength is H2O < H2S < H2Se < H2Te. Across a row in the periodic table, the acid strength of binary hydrogen compounds increases with increasing...
Brønsted-Lowry Acids and Bases
In 1923, the Brønsted–Lowry definition of acids and bases was proposed by Johannes Brønsted and Thomas Lowry. According to this theory, a Brønsted acid is defined as a species that donates a proton in a chemical reaction and gets converted to its conjugate base. A Brønsted base is defined as a species that accepts a proton in a chemical reaction and gets converted into its conjugate acid. These transfers of protons are caused by the displacement of electrons in these reactions, which is...
Acid Halides to Carboxylic Acids: Hydrolysis
Hydrolysis of acid halides is a nucleophilic acyl substitution reaction in which acid halides react with water to give carboxylic acids. The reaction occurs readily and does not require acid or a base catalyst.
As shown below, the mechanism involves a nucleophilic attack by water at the carbonyl carbon to form a tetrahedral intermediate. This is followed by the reformation of the carbon–oxygen π bond along with the departure of a halide ion. A final proton transfer step yields carboxylic acid...
As shown below, the mechanism involves a nucleophilic attack by water at the carbonyl carbon to form a tetrahedral intermediate. This is followed by the reformation of the carbon–oxygen π bond along with the departure of a halide ion. A final proton transfer step yields carboxylic acid...
Acid Halides to Esters: Alcoholysis
Alcoholysis is a nucleophilic acyl substitution reaction in which an alcohol functions as a nucleophile. Acid halides react with alcohol to produce esters. The mechanism proceeds in three steps:


