离子N-B-N和B-N-B替代相似物:一个理论分析
Khalid AlKaabi1, Prasad L V K Dasari, Roald Hoffmann
1Baker Laboratory, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA.
Journal of the American Chemical Society
|June 29, 2012
概括
新的计算探索- (B-N) 替代的环,揭示了N-B-N离子和B-N-B离子的独特稳定性模式. 这项研究预测了新的,高度稳定的B-N化和化化合物,用于未来的合成.
科学领域:
- 计算化学计算化学
- 无机化学 无机化学 有机化学
- 材料科学 材料科学 材料科学
背景情况:
- - (B-N) 化合物由于其独特的电子特性和潜在的应用而引起人们的兴趣.
- 之前的研究已经探索了各种B-N异环,但对B-N替代的类系统的系统研究并不常见.
研究的目的:
- 以计算方式研究六π电子N-B-N和B-N-B替代环及其同位素的热力学稳定性和电子特性.
- 为了预测新的,热力学稳定的B-N替代化物和化物化合物.
- 探索这些新型B-N系统的反应性和潜在稳定策略.
主要方法:
- 用密度函数理论 (DFT) 的计算来确定目标分子的能量和电子结构.
- 用电荷分布的分析和与相关的基系统的比较来合理化稳定性趋势.
- 进行了对反应性,替代效应和二元化途径的初步调查.
主要成果:
- 计算显示了基于连接性 (N-B-N与B-N-B) 和电荷 (阴离子与阴离子) 的热力学稳定性的显著变化.
- 在阳离子中,N-B-N连接性得到了强烈的支持 ([C(3) BN(2) H(6) ](+),而在阳离子中,B-N-B连接性得到了强烈的支持 ([C(3) NB(2) H(6) ](-)).
- 预测,三种新的B-N替代型氨酸比实验已知的类似物稳定得多.
- 在B-N-B替代的类系统中观察到类似的稳定性趋势,这些系统的实验性特征较小.
结论:
- 这项研究为了解B-N替代芳香系统的稳定性提供了理论基础.
- 新型,热力学稳定的N-B-N和B-N-B分子,包括化物和化物,已被计算识别出来.
- 这些发现为未来的-新材料的合成和探索提供了有希望的途径.
相关概念视频
NMR Spectroscopy of Benzene Derivatives
Simple unsubstituted benzene has six aromatic protons, all chemically equivalent. Therefore, benzene exhibits only a singlet peak at δ 7.3 ppm in the 1H NMR spectrum. The observed shift is far downfield because the aromatic ring current strongly deshields the protons. Any substitution on the benzene ring makes the aromatic protons nonequivalent, and the protons split each other. The peak is, therefore, no longer a singlet and the splitting pattern and their associated coupling constants depend...
Nomenclature of Aromatic Compounds with Multiple Substituents
When more than one substituent is present on the benzene ring, the IUPAC nomenclature depends on the number of substituents present.
For disubstituted benzene derivatives, with two groups attached to the benzene ring, three constitutional isomers are possible. For example, consider dimethyl benzene, often called xylene, where the second methyl group can be substituted at the second, third, or fourth carbon. The relative position of the substituents is represented by prefixes ortho, meta, or...
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Nomenclature of Aromatic Compounds with a Single Substituent
Benzene is the simplest aromatic hydrocarbon or arene. The IUPAC names for simple monosubstituted benzene derivatives are derived by adding the substituent's name as a prefix to the parent benzene. For example, halobenzene, where the halogen could be fluoro (F), chloro (Cl), bromo (Br), and iodo (I).
Electrophilic Aromatic Substitution: Nitration of Benzene
The nitration of benzene is an example of an electrophilic aromatic substitution reaction. It involves the formation of a very powerful electrophile, the nitronium ion, which is linear in shape. The reaction occurs through the interaction of two strong acids, sulfuric and nitric acid.
Structure of Benzene: Kekulé Model
In 1865, August Kekule suggested the structure of benzene according to the structural theory of organic chemistry based on the three assertions—formula of benzene is C6H6, all the hydrogens of benzene are equivalent, and each carbon must have four bonds due to its tetravalency.
He proposed that benzene has a cyclic structure of six carbon atoms attached to one hydrogen atom each, with three alternating pi bonds.
He proposed that benzene has a cyclic structure of six carbon atoms attached to one hydrogen atom each, with three alternating pi bonds.
Nucleophilic Aromatic Substitution: Elimination–Addition
Simple aryl halides do not react with nucleophiles. However, nucleophilic aromatic substitutions can be forced under certain conditions, such as high temperatures or strong bases. The mechanism of substitution under such conditions involves the highly unstable and reactive benzyne intermediate. Benzyne contains equivalent carbon centers at both ends of the triple bond, each of which is equally susceptible to nucleophilic attack. This 50–50 distribution of products is confirmed through isotopic...


