関連する実験動画
Updated: Jul 8, 2026

09:31
Calcium Carbonate Formation in the Presence of Biopolymeric Additives
Published on: May 14, 2019
アロマティックな炭素-炭素二重結合の水添加物の脱水のための均衡定数
Joykrishna Dey1, AnnMarie C O'Donoghue, Rory A More O'Ferrall
1Department of Chemistry and Centre for Synthesis and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland.
Journal of the American Chemical Society
|July 18, 2002
まとめ
この研究では,形成の自由エネルギーを計算するために置換法を使用して,芳香水素を脱水させるための均衡定数について報告しています. このアプローチは,アロマティックおよび反アロマティック化合物を含む様々な炭化水素の熱力学データを拡張します.
科学分野:
- 物理化学 物理化学について
- 熱力学は熱力学である.
- 有機化学 オーガニック・ケミストリー
背景:
- 正確な熱力学データは,化学反応を理解するために不可欠です.
- 水素のような複雑な分子の形成の自由エネルギーの計算は難しいかもしれません.
- 既存の方法は,幅広い芳香系および反芳香系をカバーしていない可能性があります.
研究 の 目的:
- ベンゼン,ナフタレン,フェナントレン,アントラセンの水酸化物の脱水のための均衡定数 (K(de)) を決定する.
- これらの水素の形成の自由エネルギー (DeltaG ((o) ((f) ((aq)) を推定するための置換法を開発し,適用する.
- 熱力学計算の適用範囲を,より広い範囲の不飽和有機化合物にも拡大する.
主な方法:
- マザー炭化水素とアルコールの熱力学データ (形成熱,エントロピー,移動の自由エネルギー) を利用した.
- 構造的依存関係 (主,次,三次,循環,アリル,ベンジル) を考慮して,ヒドロキシル群置換に関連する自由エネルギーインクリメント (DeltaG(OH)) を推定した.
- 水素,水,および芳香炭化水素産物の形成の自由エネルギーを組み合わせて脱水するための計算された均衡定数.
主要な成果:
- アロマティック水素の脱水反応における報告された均衡定数 (K ((de)) とその負のログ数 (pK ((de)) である.
- デルタG (OH) がアルコール構造によって変化し,ゲミナル相互作用により最大5kcalmol (−1) の差異があることが示された.
- 取得したpK(de) 値はベンゼンで-22.2からサイクロブタディエンで+28.4までであり,芳香度とストレンスと相関しています.
- 形成データの自由エネルギーを拡張するために,置換効果 (DeltaG ((OH)) とDeltaG ((pi)) の有用性を示しました.
結論:
- 置換物法では,芳香水素の熱力学的性質を計算するための信頼できる方法を提供します.
- pK (de) 値は,芳香系の安定性と,抗芳香性およびストレインされた不飽和化合物の不安定性を強調しています.
- このアプローチは,有機分子形成の計算可能な自由エネルギーの範囲を大幅に拡大します.
関連する概念動画
Water: A Bronsted-Lowry Acid and Base
The reaction between a Brønsted-Lowry acid and water is called acid ionization. For example, when hydrogen fluoride dissolves in water and ionizes, protons are transferred from hydrogen fluoride molecules to water molecules, yielding hydronium ions and fluoride ions:
Factors Affecting Solubility
Compared with pure water, the solubility of an ionic compound is less in aqueous solutions containing a common ion (one also produced by dissolution of the ionic compound). This is an example of a phenomenon known as the common ion effect, which is a consequence of the law of mass action that may be explained using Le Chȃtelier’s principle. Consider the dissolution of silver iodide:
Balancing Redox Equations
Electrochemistry is the science involved in the interconversion of electrical and chemical reactions. Such reactions are called reduction-oxidation, or redox reactions. These important reactions are defined by changes in oxidation states for one or more reactant elements and include a subset of reactions involving the transfer of electrons between reactant species. Electrochemistry as a field has evolved to yield sufficient insights on the fundamental principles of redox chemistry and multiple...
Solubility Equilibria: Overview
When a substance such as sodium chloride is added to water, it dissolves, forming an aqueous solution. The extent of dissolution is called solubility. The process of dissolution can exist in equilibrium, just like other chemical processes. Solubility equilibria are also called precipitation equilibria because the process of solubility can be reversible. The reverse of the solubility process is called precipitation.
Solubility is important in biological and environmental processes. A notable...
Solubility is important in biological and environmental processes. A notable...
Solubility Equilibria: Ionic Product of Water
Pure water is a weak electrolyte; only a small amount ionizes into hydrogen and hydroxide ions. At any given temperature, the concentration of undissociated water is almost constant, so the ionic product of water is the product of the hydrogen and hydroxide ion concentrations, denoted as Kw. The square root of Kw gives the individual ion concentrations.
The ionic product of water varies with temperature, and its value is 1.0 x 10−14 at standard experimental conditions. Per Le Chatelier's...
The ionic product of water varies with temperature, and its value is 1.0 x 10−14 at standard experimental conditions. Per Le Chatelier's...
Carbonation Shrinkage
Atmospheric CO2 penetrates the concrete's pores and, in the presence of moisture, forms carbonic acid, which then reacts with calcium hydroxide in the hydrated cement, forming calcium carbonate. This process reduces the concrete's volume and is termed carbonation shrinkage.
The concrete's permeability is slightly reduced as calcium carbonate produced during the reaction fills its pores. Furthermore, its strength is slightly enhanced as the water released during the reaction facilitates the...
The concrete's permeability is slightly reduced as calcium carbonate produced during the reaction fills its pores. Furthermore, its strength is slightly enhanced as the water released during the reaction facilitates the...

