氧化物作为乙烯酸乙烯的肥化中的一般基
1School of Chemistry, University of Costa Rica, 2060 Costa Rica. jmata@cariari.ucr.ac.cr
Journal of the American Chemical Society
|March 7, 2002
概括
乙酸乙烯的肥化涉及四面体中间形成作为速度决定的步骤. 这项研究揭示了一种新的机制,涉及水的核性相互作用与氧化离子的一般基辅助.
科学领域:
- 物理化学 物理化学
- 有机化学 有机化学
背景情况:
- 乙酸乙烯的肥化是一种关键的水解反应.
- 普遍接受的机制涉及氧化离子的直接核友性攻击.
研究的目的:
- 阐明乙酸乙烯肥化的详细机制.
- 研究水和氧化离子在过渡状态中的作用.
主要方法:
- 使用H(2) O/D(2) O混合物的质子库存实验.
- 对二次速率常数 (k(2) 的动态分析.
主要成果:
- 速率常数在H(2) O/D(2) O混合物中遵循复杂的关系.
- 数据支持一个四面体中间形成是限制速度的机制.
结论:
- 过渡状态涉及水的核性相互作用与氧化物的一般基辅助.
- 这与直接核友性碰撞模型形成鲜明对比.
- 这些发现与之前的重原子动态同位素效应研究一致.
相关概念视频
Titration Calculations: Weak Acid - Strong Base
Calculating pH for Titration Solutions: Weak Acid/Strong Base
For the titration of 25.00 mL of 0.100 M CH3CO2H with 0.100 M NaOH, the reaction can be represented as:
For the titration of 25.00 mL of 0.100 M CH3CO2H with 0.100 M NaOH, the reaction can be represented as:
Acidity of 1-Alkynes
The acidic strength of hydrocarbons follows the order: Alkynes > Alkenes > Alkanes. The strength of an acid is commonly expressed in units of pKa — the lower the pKa, the stronger the acid. Among the hydrocarbons, terminal alkynes have lower pKa values and are, therefore, more acidic. For example, the pKa values for ethane, ethene, and acetylene are 51, 44, and 25, respectively, as shown here.
Esters to Carboxylic Acids: Saponification
Esters can be hydrolyzed to carboxylic acids under acidic or basic conditions. Base-promoted hydrolysis of esters is a nucleophilic acyl substitution reaction in which esters react with an aqueous base, followed by an acid to give carboxylic acids. This reaction is also known as saponification because it forms the basis for making soaps from fats.
The reaction requires a base in stoichiometric amounts, which participates in the reaction and is not regenerated later. So, the base acts as a...
The reaction requires a base in stoichiometric amounts, which participates in the reaction and is not regenerated later. So, the base acts as a...
Esters to Carboxylic Acids: Acid-Catalyzed Hydrolysis
Hydrolysis of esters under acidic conditions proceeds through a nucleophilic acyl substitution. In the presence of excess water, the reaction proceeds in a reversible manner, forming carboxylic acids and alcohols.
During hydrolysis, the ester is first activated towards nucleophilic attack through the protonation of the carboxyl oxygen atom by the acid catalyst. The protonation makes the ester carbonyl carbon more electrophilic. In the next step, water acts as a nucleophile and adds to the...
During hydrolysis, the ester is first activated towards nucleophilic attack through the protonation of the carboxyl oxygen atom by the acid catalyst. The protonation makes the ester carbonyl carbon more electrophilic. In the next step, water acts as a nucleophile and adds to the...
Factors Affecting α-Alkylation of Ketones: Choice of Base
α-Alkylation of ketones is achieved in the presence of alkyl halides and a base. The reaction proceeds via the formation of an enolate ion followed by nucleophilic substitution. The choice of base employed is essential as it is the key factor in determining the reaction outcome.
The reaction involving bases like EtO− whose conjugate acid EtOH (pKa = 15.9) is stronger than the ketone (pKa = 19.2) results in an equilibrium mixture with higher ketone concentration. As a consequence, side reactions...
The reaction involving bases like EtO− whose conjugate acid EtOH (pKa = 15.9) is stronger than the ketone (pKa = 19.2) results in an equilibrium mixture with higher ketone concentration. As a consequence, side reactions...
Solution Composition During Acid/Base Titrations
The titration of a weak acid with a strong base results in the formation of water and the conjugate base of the acid. For instance, titrating acetic acid with sodium hydroxide leads to the formation of water and sodium acetate. A solution of acetic acid and sodium acetate constitutes a buffer whose relative concentration at different stages of the titration is indicated by the α values, which represent percentages of the weak acid and its conjugate base.
The α0 and α1 values represent the...
The α0 and α1 values represent the...


