大气中的化物反应的定量动力学:高阶动态相关性,不和性和落差效应都很重要
Bo Long1, Yu Xia1, Donald G Truhlar2
1College of Materials Science and Engineering, Guizhou Minzu University, Guiyang550025, China.
Journal of the American Chemical Society
|October 20, 2022
概括
计算化学确定了基 (HO2) 与甲 (HCHO),乙 (CH3CHO) 和三乙 (CF3CHO) 的反应速率常数. 这些动力学对于理解大气化学和建模至关重要.
科学领域:
- 大气化学
- 计算化学
- 化学动力学
背景情况:
- 准确的动力数据对于了解大气过程至关重要,包括关键物种的来源和沉积点.
- 在大气温度和压力范围广泛的反应动力学的实验室确定具有挑战性.
研究的目的:
- 通过计算来确定涉及基 (HO2) 和三种化物:甲 (HCHO),乙 (CH3CHO) 和三乙 (CF3CHO) 的反应的定量速率常数.
- 研究这些反应的压力依赖性及其在大气模型中的意义.
主要方法:
- 采用双层计算策略,将高层电子结构理论 (超越-CCSD(T) 和CCSD(T) -F12a) 与变化过渡状态理论 (VTST) 结合起来,包括道校正.
- 使用A级/B级方法计算的高压限速常数,根据更高级计算 (CCSDTQ(P) /CBS) 进行验证.
- 使用系统特定的量子RRK理论 (SS-QRRK) 和能量粒度主方程确定压力依赖的速率常数,显示方法之间的良好一致性.
主要成果:
- 发现无性是一个显著的因素,增加了所有三个反应的速率常数.
- HO2与HCHO的反应表现出显著的压力依赖.
- HO2与CF3CHO的反应显示出极少的压力依赖性.
结论:
- HO2 + HCHO反应代表了大气中甲的重要沉积点.
- 确定HO2 + CF3CHO反应是三乙的主要大气沉积点.
- 使用的计算方法为大气模型提供可靠的动力参数.
更多相关视频
08:15Temperature-programmed Deoxygenation of Acetic Acid on Molybdenum Carbide Catalysts
Published on: February 7, 2017
11.5K
07:24Combustion Chemistry of Fuels: Quantitative Speciation Data Obtained from an Atmospheric High-temperature Flow Reactor with Coupled Molecular-beam Mass Spectrometer
Published on: February 19, 2018
10.2K
相关概念视频
01:21Acid-Catalyzed α-Halogenation of Aldehydes and Ketones
4.0K
By replacing an α-hydrogen with a halogen, acid-catalyzed α-halogenation of aldehydes or ketones yields a monohalogenated product
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
4.0K
02:14SN2 Reaction: Kinetics
8.6K
Kinetic Studies and Significance
In a chemical reaction, a relationship exists between the concentration of reactants and the rate at which the reaction proceeds. The study to measure this relationship is known as the kinetics of a chemical reaction. Kinetic studies are used to deduce the rate law of a chemical reaction, which provides information about the species involved during the transition state of the rate-determining step. Thus, kinetic studies help to derive the mechanism of a...
In a chemical reaction, a relationship exists between the concentration of reactants and the rate at which the reaction proceeds. The study to measure this relationship is known as the kinetics of a chemical reaction. Kinetic studies are used to deduce the rate law of a chemical reaction, which provides information about the species involved during the transition state of the rate-determining step. Thus, kinetic studies help to derive the mechanism of a...
8.6K
02:45Acid-Catalyzed Hydration of Alkenes
14.7K
Alkenes react with water in the presence of an acid to form an alcohol. In the absence of acid, hydration of alkenes does not occur at a significant rate, and the acid is not consumed in the reaction. Therefore, alkene hydration is an acid-catalyzed reaction.
14.7K
02:36Regioselectivity and Stereochemistry of Hydroboration
8.3K
A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn...
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn...
8.3K
01:19Aldehydes and Ketones with Alcohols: Hemiacetal Formation
6.8K
Similar to water, alcohols can add to the carbonyl carbon of the aldehydes and ketones. The addition of one molecule of alcohol to the carbonyl compound forms the hemiacetal or half acetal. As depicted below, in a hemiacetal, the carbon is directly linked to an OH and OR group.
6.8K
03:09Measuring Reaction Rates
25.6K
Polarimetry finds application in chemical kinetics to measure the concentration and reaction kinetics of optically active substances during a chemical reaction. Optically active substances have the capability of rotating the plane of polarization of linearly polarized light passing through them—a feature called optical rotation. Optical activity is attributed to the molecular structure of substances. Normal monochromatic light is unpolarized and possesses oscillations of the electrical...
25.6K