アモニアモノヒドレートII相の結晶構造
A Dominic Fortes1, Emmanuelle Suard, Marie-Hélène Lemée-Cailleau
1Centre for Planetary Sciences at UCL/Birkbeck, Gower Street, London, WC1E 6BT, United Kingdom. andrew.fortes@ucl.ac.uk
Journal of the American Chemical Society
|September 17, 2009
まとめ
私たちは,中性子 difraktionと計算方法を使用して,アンモニアモノヒドレート第II相 (AMHII) の結晶構造を決定しました. これは,AMH IIにおける複雑な水素結合ネットワークを明らかにし,ステキオメトリックアンモニア水合物における最初の構造である.
科学分野:
- クリスタログラフィーです.
- マテリアルサイエンス 材料科学
- コンピューティング・ケミストリー
背景:
- アンモニア水素の高圧相は十分に理解されていません.
- これらの相の複雑な分子構造を決定することは困難です.
研究 の 目的:
- 高圧下でのアンモニア単水酸二相 (AMH II) の結晶構造を決定する.
- AMH II.内の水素結合ネットワークを解明する.
主な方法:
- 密度関数理論を用いた Ab initio 計算構造予測.
- 直接空間法を用いた中性子粉の difraktion データからの構造溶液.
- 高解像度の微分光度計を使用して中性子の微分光度データを収集する.
主要な成果:
- AMH IIの結晶構造は,空間群Pbca.で決定されました.
- AMH IIは,オーダーされた水素結合によって形成されたテッセル化された五角形のシートを展示しています.
- 構造は,ユニークな水素結合配列によって特徴付けられています.
結論:
- これは,高圧ステキオメトリックアンモニア水合物で決定された最初の複雑な分子構造です.
- 計算による予測は,実験的な微分データと密接に一致します.
- 決定された構造は,圧力下でのアンモニアと水の相互作用に関する重要な洞察を提供します.
さらに関連する動画
09:16X-ray Powder Diffraction in Conservation Science: Towards Routine Crystal Structure Determination of Corrosion Products on Heritage Art Objects
Published on: June 8, 2016
10:10Neutron Crystallography Data Collection and Processing for Modelling Hydrogen Atoms in Protein Structures
Published on: December 1, 2020
関連する概念動画
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...
02:42Ionic Crystal Structures
Ionic crystals consist of two or more different kinds of ions that usually have different sizes. The packing of these ions into a crystal structure is more complex than the packing of metal atoms that are the same size.
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...
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...
01:12Nomenclature of Secondary and Tertiary Amines
The secondary and tertiary amines are derivatives of ammonia, where two and three of its hydrogens are replaced by alkyl groups, respectively. Secondary and tertiary amines can be symmetrical with identical alkyl groups attached to the nitrogen atom or unsymmetrical when more than one type of alkyl group is present. The standard nomenclature of secondary and tertiary amines is similar to the names given to the primary amines. They are generally named alkylamines. As depicted in Figure 1, for...
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Tetrahedral Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
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...