水中のアリファ酸アミンの間のメチル群の移動
Brian P Callahan1, Richard Wolfenden
1Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, 27599-7260, USA.
Journal of the American Chemical Society
|January 9, 2003
まとめ
グライシンのデカルボキシル化により,さらに反応するメチラミンが生成されます. メチラミンは水の中で不釣り合いになり,他のメチラミンを生成し,化学運動学の新しい発見である.
科学分野:
- 有機化学 オーガニック・ケミストリー
- 化学動力学 化学動力学
- 反応メカニズム 反応メカニズム
背景:
- 高温で水溶液でグリシンをデカルボキシル化すると,メチラミンが得られます.
- 予期せぬことに,ダイメチラミンとトリメチラミンも現れ,さらなる反応が示唆された.
研究 の 目的:
- グリシンからメチラミンの自発的形成を調査する.
- 水性媒体におけるメチラミン不均衡化反応の提案を調査する.
- メチラミン変換の運動学とメカニズムを解明する.
主な方法:
- 時間の経過とともにアミン産物形成を監視する.
- アミンバッファを使用してpHの関数としての反応速度を調査する.
- N,N-ジメチル-1,3-プロパンダイアミンにおけるメチル群の移動を研究する.
- メチル群ドナーとしてのスルフォニウムイオンの反応性を比較する.
主要な成果:
- メチラミン,ジメチラミン,トリメチラミンが相互変換することが観察されました.
- メチラミン不均衡の割合は,プロトン化と非プロトン化アミンの等価な濃度でピークに達した.
- ダイアミンにおけるメチル群の移動は,ファーストオーダー運動に従った.
- トリメチルスルフォニウムイオンは,メチル群移転においてテトラメチルアモニウムイオンよりも有意に高い反応性を示した.
結論:
- グリシンデカルボキシル化は,水中のメチラミン不均衡反応のカスケードを開始します.
- pHに依存する運動学は,プロトン化と非プロトン化アミン種の両方を含むメカニズムをサポートします.
- メチル基移転反応は,メチル化剤と受容体の構造によって影響を受けます.
関連する概念動画
01:07Acid Halides to Amides: Aminolysis
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...
01:21Basicity of Aliphatic Amines
Amines can behave as Brønsted–Lowry bases by accepting a proton from the acid to form corresponding conjugate acids. Due to a lone pair of nonbonding electrons, aliphatic amines can also act as Lewis bases by forming a covalent bond with an electrophile.
To measure the basicity of amines, two conventions are generally used. The first defines Kb as the basicity constant for the deprotonation reaction of water by the amine, as presented in Figure 1. Conventionally, lower Kb indicates higher...
To measure the basicity of amines, two conventions are generally used. The first defines Kb as the basicity constant for the deprotonation reaction of water by the amine, as presented in Figure 1. Conventionally, lower Kb indicates higher...
01:30Preparation of Amines: Alkylation of Ammonia and Amines
Alkylation is one of the methods used to prepare amines. Direct alkylation of ammonia or a primary amine with an alkyl halide gives polyalkylated amines along with a quaternary ammonium salt through successive SN2 reactions. This process of making the quaternary salt through the direct alkylation method is called exhaustive alkylation.
Each alkylation step makes the nitrogen center more nucleophilic, which triggers successive alkylations until a quaternary ammonium salt is formed. Considering...
Each alkylation step makes the nitrogen center more nucleophilic, which triggers successive alkylations until a quaternary ammonium salt is formed. Considering...
01:23Aldehydes and Ketones with Amines: Imine Formation Mechanism
Imine formation involves the addition of carbonyl compounds to a primary amine. It begins with the generation of carbinolamine through a series of steps involving an initial nucleophilic attack and then several proton transfer reactions. The second part includes the elimination of water, as a leaving group, to give the imine.
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...
01:26Physical Properties of Amines
Amines with low molecular weight are usually gaseous at room temperature, while those with high molecular weight are liquid or solids in nature. Usually, low molecular weight amines have a rotten fish-like smell. Diamines typically have a pungent smell. For instance, cadaverine and putrescine, depicted in Figure 1, are two molecules responsible for decaying tissue.
01:19NMR Spectroscopy Of Amines
In proton NMR spectroscopy, primary amines and secondary amines showcase their N–H protons as a broad signal in the chemical shift range between δ 0.5 and 5 ppm. The exact position in this range depends on several factors, including sample concentration, hydrogen bonding, and the type of solvent used. Since amine protons undergo fast proton exchange in solution, the protons are labile and therefore do not participate in any splitting with adjacent protons. Thus, the observed peak is broad and...