クラスラテット中のプロトンアミンを特定する.
Terrence M Chang1, Richard J Cooper, Evan R Williams
1Department of Chemistry, University of California , Berkeley, California 94720-1460, United States.
Journal of the American Chemical Society
|September 7, 2013
まとめ
水素化プロトン化アンモニアと20個の水分子を含んだアミンの安定した構造は,光譜を用いて特定されました. これらのマジックナンバー・クラスターはクラスラートのような構造を示し,イオンの位置が安定性と水素結合に影響を与える.
科学分野:
- 物理化学 物理化学
- 化学物理 化学物理
- スペクトル顕微鏡検査です.
背景:
- 水中の水素結合ネットワークに対するイオンの影響を調査することは極めて重要です.
- 水酸化イオンの構造を理解することで,溶解と表面活動に関する洞察が得られます.
研究 の 目的:
- 水素化プロトン化アンモニアと様々なアミンの構造と安定性を決定する.
- 構造形成におけるイオン型と水群の大きさの役割を明らかにする.
主な方法:
- 赤外線光解離 (IRPD) スペクトロスコーピー. 赤外線光解離 (IRPD) スペクトロスコーピー. 赤外線光解離 (IRPD) スペクトロスコーピー. 赤外線光解離 (IRPD) スペクトロスコーピー.
- 133 Kのブラックボディ赤外線放射解離 (BIRD) スペクトロスコーピー
- 基準イオン (Rb+,プロトンテートブチラミン) と比較.
主要な成果:
- ほとんどのイオンには20個の水分子を含んだマジックナンバー・クラスター (MNC) が観察され,安定したクラスラート状の構造を示した.
- テトラメチラモニウムとより小さい/より大きなクラスターは,非クラスレート構造を示した.
- 内側にはプロトナートアンモニアがみられ,クラスラートの表面にはプロトナートメチルとn-ヘプチラミンがみられた.
結論:
- 質量だけでなく,水素結合の数と向きがクラスタの安定性を決定する.
- 実験的発見は,イオンと水の相互作用に関する計算研究のための基準として機能します.
さらに関連する動画
関連する概念動画
Acid 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...
Structure 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...
Basicity 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...
Preparation of 1° Amines: Hofmann and Curtius Rearrangement Mechanism
The Hofmann and Curtius rearrangement reactions can be applied to synthesize primary amines from carboxylic acid derivatives such as amides and acyl azides. In the Hofmann rearrangement, a primary amide undergoes deprotonation in the presence of a base, followed by halogenation to generate an N-haloamide. A second proton abstraction produces a stabilized anionic species, which rearranges to an isocyanate intermediate via an alkyl group migration from the carbonyl carbon to the neighboring...
NMR 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...
Basicity of Heterocyclic Aromatic Amines
Heterocyclic amines, where the N atom is a part of an alicyclic system, are similar in basicity to alkylamines. Interestingly, the heterocyclic amine having a nitrogen atom as part of an aromatic ring has much less basicity than its corresponding alicyclic counterpart. For this reason, as presented in Figure 1, piperidine (pKb = 2.8) is significantly more basic than pyridine (pKb = 8.8).


