克里基中间体与OH作为大气胺的清洁剂很好地竞争
Bo Long1, Chaolu Xie2, Donald G Truhlar3
1College of Materials Science and Engineering, Guizhou Minzu University, Guiyang 550025, China.
Journal of the American Chemical Society
|June 13, 2025
概括
稳定Criegee中间体 (sCI) 与胺迅速反应,显著影响大气化学. 这些反应比先前的假设更快,使得sCI成为大气胺的主要沉积物.
科学领域:
- 大气化学
- 化学动力学
- 气候模型
背景情况:
- 稳定Criegee中间体 (sCI) 在大气化学中至关重要.
- 了解它们的反应对于准确的气候模型至关重要.
研究的目的:
- 调查sCI与胺的反应动力学.
- 解释这些快速双分子反应的机制.
主要方法:
- 电子结构计算
- 运动计算
- 变量过渡状态理论
主要成果:
- 确定了一种涉及碳氧添加和转移的通用反应机制.
- sCI-胺反应的速率常数非常快 (1-5 × 10−10 cm3分子−1 s−1).
- 这些反应明显快于与碳酸和OH基反应的sCI反应.
结论:
- 大气中的胺主要由sCIs去除,而不是之前假设的OH基.
- 快速的动力学需要重新评估有关胺降解途径的大气模型.
相关概念视频
Preparation of 1° Amines: Hofmann and Curtius Rearrangement Mechanism
3.4K
The Hofmann and Curtius rearrangement reactions can be applied to synthesize primary amines from carboxylic acid derivatives such as amides and acyl azides. In the Hofmann rearrangement, a primary amide undergoes deprotonation in the presence of a base, followed by halogenation to generate an N-haloamide. A second proton abstraction produces a stabilized anionic species, which rearranges to an isocyanate intermediate via an alkyl group migration from the carbonyl carbon to the neighboring...
3.4K
Amines to Alkenes: Hofmann Elimination
2.5K
Alkenes can be obtained from amines via an E2 elimination. The amine is first converted into a good leaving group, such as a quaternary ammonium salt. This is accomplished by treating the amine with an excess of alkyl halide, which results in a halide salt. Next, the halide salt is transformed into a hydroxide salt that functions as a base to enable elimination.
Under thermal conditions, the hydroxide can abstract a proton from the β carbon; this generates an alkene with the simultaneous...
Under thermal conditions, the hydroxide can abstract a proton from the β carbon; this generates an alkene with the simultaneous...
2.5K
Preparation of Amides
3.0K
Amides are synthesized by treating carboxylic acids with amines in the presence of dehydrating agents like dicyclohexylcarbodiimide (DCC).
The DCC-promoted synthesis of amides begins with the protonation of DCC by carboxylic acid. The protonation makes it a better acceptor. Next, the addition of carboxylate to the protonated carbodiimide gives a reactive acylating agent.
Subsequently, the amine acts as a nucleophile that attacks the acylating agent to form a tetrahedral intermediate. In the...
The DCC-promoted synthesis of amides begins with the protonation of DCC by carboxylic acid. The protonation makes it a better acceptor. Next, the addition of carboxylate to the protonated carbodiimide gives a reactive acylating agent.
Subsequently, the amine acts as a nucleophile that attacks the acylating agent to form a tetrahedral intermediate. In the...
3.0K
Preparation of 1° Amines: Hofmann and Curtius Rearrangement Overview
3.2K
In the presence of an aqueous base and a halogen, primary amides can lose the carbonyl (as carbon dioxide) and undergo rearrangement to form primary amines. This reaction, called the Hofmann rearrangement, can produce primary amines (aryl and alkyl) in high yields without contamination by secondary and tertiary amines.
3.2K
Acid Halides to Amides: Aminolysis
2.7K
Aminolysis is a nucleophilic acyl substitution reaction, where ammonia or amines act as nucleophiles to give the substitution product. Acid halides react with ammonia, primary amines, and secondary amines to yield primary, secondary, and tertiary amides, respectively.
In the first step of the aminolysis mechanism, the amine attacks the carbonyl carbon of the acyl chloride to form a tetrahedral intermediate. In the second step, the carbonyl group is re-formed with the elimination of a chloride...
In the first step of the aminolysis mechanism, the amine attacks the carbonyl carbon of the acyl chloride to form a tetrahedral intermediate. In the second step, the carbonyl group is re-formed with the elimination of a chloride...
2.7K
Amides to Carboxylic Acids: Hydrolysis
3.1K
Amides can undergo either acid-catalyzed hydrolysis or base-promoted hydrolysis through a typical nucleophilic acyl substitution. Each hydrolysis requires severe conditions.
Acid-catalyzed hydrolysis:
Hydrolysis of amides under acidic conditions yields carboxylic acids. Since the reaction occurs slowly, hydrolysis requires the conditions of heat.
The mechanism begins with the protonation of the carbonyl oxygen by the acid catalyst. The protonation makes the amide carbonyl carbon more...
Acid-catalyzed hydrolysis:
Hydrolysis of amides under acidic conditions yields carboxylic acids. Since the reaction occurs slowly, hydrolysis requires the conditions of heat.
The mechanism begins with the protonation of the carbonyl oxygen by the acid catalyst. The protonation makes the amide carbonyl carbon more...
3.1K


