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Determination of the Gas-phase Acidities of Oligopeptides
Published on: June 24, 2013
フォスファ (III) -およびフォスファ (V) -グアニジン化合物の構成に関する研究
Natalie E Mansfield1, Joanna Grundy, Martyn P Coles
1Department of Chemistry, University of Sussex, Falmer, Brighton BN1 9QJ, UK.
Journal of the American Chemical Society
|October 19, 2006
まとめ
フォスファ (III) -とフォスファ (V) -グアニジンの置換物質の指向は,ステリック要因の影響を受けます. P-ディサイクロヘキシル誘導体は,P-ディフェニル類似体と比較して,特に酸化された形態では,明確な同位体好みを表しています.
科学分野:
- オーガノフォスファルス 化学 化学
- 超分子化学 超分子化学
- コンピューティング・ケミストリー
背景:
- フォスファ (III) -およびフォスファ (V) -グアニジンは,多様な用途を持つ多用途化合物です.
- 置換剤の分布を理解することは,それらの化学的行動と性質を予測するために極めて重要です.
研究 の 目的:
- フォスファ (III) -とフォスファ (V) -グアニジンにおける置換剤の分布を,光学,結晶学,計算的方法を用いて調査する.
- これらのシステムにおける形状的好みと同位体分布を左右する要因を解明する.
主な方法:
- 核磁共振 (NMR) スペクトロスコーピーは,同位体混合物と構成上の好みを分析します.
- 低エネルギー構造と電子因子をモデル化するための密度関数理論 (DFT) 計算.
- 固体構造と置換物質の配列を決定するためのX線結晶学.
主要な成果:
- P-ディフェニル置換化合物は,主にフォスファ (III) システムにおけるE (syn) - (alpha) 構成を採用する.
- P-ディサイクロヘキシル誘導体は,同位体混合物として存在し,DFTはβ構成を好むことを示唆しています.
- 酸化されたフォスファ (((V) 化合物は,P置換基に基づいた明確な同位体偏好を示し,Z (((syn) - (((beta) 構成で観察された分子内E...HN相互作用があります.
結論:
- 電子的な論点ではなく,ステリック要因が,これらのフォスファ-グアニジン系における観察された置換物指向偏好の主な要因である.
- この研究は,有機リン化合物の構造-性質関係に関する貴重な洞察を提供します.
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03:05Acid Strength and Molecular Structure
Binary Acids and Bases
In the absence of any leveling effect, the acid strength of binary compounds of hydrogen with nonmetals (A) increases as the H-A bond strength decreases down a group in the periodic table. For group 17, the order of increasing acidity is HF < HCl < HBr < HI. Likewise, for group 16, the order of increasing acid strength is H2O < H2S < H2Se < H2Te. Across a row in the periodic table, the acid strength of binary hydrogen compounds increases with increasing...
In the absence of any leveling effect, the acid strength of binary compounds of hydrogen with nonmetals (A) increases as the H-A bond strength decreases down a group in the periodic table. For group 17, the order of increasing acidity is HF < HCl < HBr < HI. Likewise, for group 16, the order of increasing acid strength is H2O < H2S < H2Se < H2Te. Across a row in the periodic table, the acid strength of binary hydrogen compounds increases with increasing...
01:16Nomenclature of Carboxylic Acid Derivatives: Acid Halides, Esters, and Acid Anhydrides
Naming Acid Halides
The IUPAC and common names of acid halides are derived from the corresponding carboxylic acids, by changing “ic acid” to “yl halide.” For example, as shown below, the IUPAC name ethanoyl chloride is derived from ethanoic acid, and the common name, acetyl chloride, is obtained from acetic acid.
The IUPAC and common names of acid halides are derived from the corresponding carboxylic acids, by changing “ic acid” to “yl halide.” For example, as shown below, the IUPAC name ethanoyl chloride is derived from ethanoic acid, and the common name, acetyl chloride, is obtained from acetic acid.
01:28Structures of Carboxylic Acid Derivatives
Structure of Carboxylic Acid Derivatives
Carboxylic acid derivatives contain an acyl group attached to a heteroatom such as chlorine, oxygen, or nitrogen. The carbonyl carbon and oxygen are both sp2-hybridized with an unhybridized p orbital.
The three sp2 orbitals of the carbonyl carbon form three σ bonds, one each with the carbonyl oxygen, the α carbon, and the heteroatom, whereas the other two sp2 orbitals of the carbonyl oxygen are occupied by the lone pairs. Further, the unhybridized p...
Carboxylic acid derivatives contain an acyl group attached to a heteroatom such as chlorine, oxygen, or nitrogen. The carbonyl carbon and oxygen are both sp2-hybridized with an unhybridized p orbital.
The three sp2 orbitals of the carbonyl carbon form three σ bonds, one each with the carbonyl oxygen, the α carbon, and the heteroatom, whereas the other two sp2 orbitals of the carbonyl oxygen are occupied by the lone pairs. Further, the unhybridized p...
01:14Acid Halides to Ketones: Gilman Reagent
Lithium dialkyl cuprate, also known as Gilman reagents, selectively reduces acid halides to ketones. The acid chloride is treated with Gilman reagent at −78 °C in the presence of ether solution to produce a ketone in good yield.
As shown below, the mechanism proceeds in two steps. First, one of the alkyl groups of the reagent acts as a nucleophile and attacks the acyl carbon of the acid chloride to form a tetrahedral intermediate. This is followed by the reformation of the carbon–oxygen double...
As shown below, the mechanism proceeds in two steps. First, one of the alkyl groups of the reagent acts as a nucleophile and attacks the acyl carbon of the acid chloride to form a tetrahedral intermediate. This is followed by the reformation of the carbon–oxygen double...
01:19Structure of Amines
The hybridized nitrogen atom in amines possesses a lone pair of electrons and is bound to three substituents with a bond angle of around 108°, which is less than the tetrahedral angle of 109.5°. However, the C–N–H bond angle is slightly larger at 112°, with a carbon–nitrogen bond length of 147 pm. This carbon–nitrogen bond length of of amines is longer than the carbon–oxygen bond of alcohols (143 pm) but shorter than alkanes’ carbon–carbon bond (154 pm). These aspects are illustrated in Figure...
01:23Aldehydes and Ketones with Amines: Imine Formation Mechanism
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Imines are formed under mildly acidic conditions. A pH of 4.5 is ideal for the reaction.
If the pH is low or the solution is too acidic, the reaction slows down in the...
Imines are formed under mildly acidic conditions. A pH of 4.5 is ideal for the reaction.
If the pH is low or the solution is too acidic, the reaction slows down in the...