エチルアセテートの石化化における一般的な塩基としての酸化水素
1School of Chemistry, University of Costa Rica, 2060 Costa Rica. jmata@cariari.ucr.ac.cr
Journal of the American Chemical Society
|March 7, 2002
まとめ
エチルアセテートの石化には,速度を決定するステップとして四面体の中間形成が含まれます. この研究は,水酸化イオンからの一般ベース補助による水核性相互作用を含む新しいメカニズムを明らかにしています.
科学分野:
- 物理化学 物理化学
- 有機化学 オーガニック・ケミストリー
背景:
- エチルアセテートの石化化は,エステル水解の重要な反応である.
- 一般的に受け入れられているメカニズムは,水酸化イオンによる直接的な核愛性攻撃を含む.
研究 の 目的:
- エチルアセテート肥化の詳細なメカニズムを解明する.
- 移行状態における水と水酸化物イオンの役割を調査する.
主な方法:
- H(2) O/D(2) O混合物を用いた陽子在庫実験.
- 二次速度定数 (k(2) の運動分析.
主要な成果:
- 速度定数は,H(2) O/D(2) O混合物における複雑な関係に従っている.
- このデータは,テトラエドルの中間形成が速度を制限するメカニズムを支持しています.
結論:
- 移行状態は,水による核性相互作用と,水酸化物による一般塩基の補助を含みます.
- これは,直接的な核愛性衝突モデルと対照的である.
- 発見は,以前の重原子運動同位体効果研究と一致しています.
関連する概念動画
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...


