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Related Concept Videos

Aromatic Hydrocarbon Anions: Structural Overview01:18

Aromatic Hydrocarbon Anions: Structural Overview

4.3K
Neutral hydrocarbons like cyclopentadiene with an odd number of carbon atoms and one intervening CH2 group in the ring are not aromatic. Cyclopentadiene with 4 π electrons does not satisfy the 4n + 2 π electron rule. Additionally, the intervening CH2 group is sp3 hybridized and lacks a vacant p orbital, thereby interrupting the overlap of p orbitals in a continuous manner and preventing the delocalization of π electrons throughout the ring.
Due to the absence of continuous...
4.3K
Aromatic Hydrocarbon Cations: Structural Overview01:18

Aromatic Hydrocarbon Cations: Structural Overview

4.3K
Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
Removing one hydrogen from the intervening CH2 group...
4.3K
Frost Circles for Different Conjugated Systems01:18

Frost Circles for Different Conjugated Systems

4.3K
The inscribed polygon method is consistent with Hückel’s 4n + 2 rule and helps to learn whether the given cyclic compound is aromatic or not. The compound is stable and aromatic if every bonding molecular orbital (MO) is completely filled with a pair of electrons. However, if the non-bonding or antibonding orbitals are filled with electrons, the compound is unstable and not aromatic. Consider the Frost circle diagrams for cycloalkenes containing 4 to 8 carbons.
4.3K
π Electron Effects on Chemical Shift: Aromatic and Antiaromatic Compounds01:14

π Electron Effects on Chemical Shift: Aromatic and Antiaromatic Compounds

2.0K
In aromatic compounds, such as benzene, the circulation of (4n + 2) π-electrons sets up a diamagnetic or diatropic ring current around the perimeter of the molecule. This current induces a magnetic field that opposes the external field inside the ring and reinforces it on the outside. The protons in benzene are deshielded and exhibit high chemical shifts in the range 6.5–8.5 ppm. The shielding effect at the center of the ring is evident in complex aromatic molecules, such as...
2.0K
Criteria for Aromaticity and the Hückel 4n + 2 Rule01:20

Criteria for Aromaticity and the Hückel 4n + 2 Rule

15.0K
Like benzene, cyclobutadiene and cyclooctatetraene are cyclic compounds with alternate single and double bonds. However, their chemical behavior differs from benzene, as they are unstable and not aromatic. So, what are the structural characteristics of unsaturated compounds categorized as aromatic?  
For the first time, Eric Hückel, a German chemical physicist, derived a set of structural features for a compound to be classified as aromatic. This is now known as Hückel’s rule or the 4n +...
15.0K
Five-Membered Heterocyclic Aromatic Compounds: Overview01:13

Five-Membered Heterocyclic Aromatic Compounds: Overview

6.1K
Heterocyclic aromatic compounds are cyclic compounds that are aromatic and have one or more heteroatoms—atoms other than carbon, in the ring. Depending upon the number of atoms present in the ring, they can be either five or six-membered. Examples of five-membered heterocyclic aromatic compounds include pyrrole, furan, thiophene, and imidazole. Pyrrole consists of one nitrogen atom having one lone pair of electrons. Furan and thiophene have one oxygen and one sulfur heteroatom,...
6.1K

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Preparation of a Corannulene-functionalized Hexahelicene by CopperI-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units
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Preparation of a Corannulene-functionalized Hexahelicene by CopperI-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units

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d-AO spherical aromaticity in Ce6O8.

Xiaohu Yu1, Artem R Oganov1,2,3,4, Ivan A Popov5

  • 1Department of Problems of Physics and Energetics, Moscow Institute of Physics and Technology, 9 Institutskiy Land, Dolgoprudny City, Moscow Region, 141700, Russia.

Journal of Computational Chemistry
|August 19, 2015
PubMed
Summary
This summary is machine-generated.

Researchers predict a stable, spherical cerium oxide cluster (Ce6O8) exhibiting novel d-atomic orbital (d-AO) spherical sigma (σ) aromaticity. This finding explains the cluster

Keywords:
Ce6O8chemical bondingd-AO aromaticityevolutionary programnatural bond orbital analysis

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Area of Science:

  • Inorganic Chemistry
  • Theoretical Chemistry
  • Materials Science

Background:

  • Aromaticity, initially described for pi (π) systems like benzene, has been extended to sigma (σ) and delta (δ) systems.
  • d-atomic orbital (d-AO) based spherical σ aromaticity has not been previously reported.

Purpose of the Study:

  • To predict and characterize a novel spherical cluster with d-AO based spherical σ aromaticity.
  • To explain the unusual geometry and stability of the predicted cluster.

Main Methods:

  • Evolutionary algorithm USPEX for cluster prediction.
  • Density Functional Theory (DFT)+U calculations for electronic structure analysis.
  • Natural Bond Orbital (NBO) analysis, Adaptive Natural Density Partitioning (ANDP), Electron Localization Function (ELF), and partial charge plots for bonding analysis.

Main Results:

  • Prediction of a highly stable, spherical bare Ce6O8 cluster.
  • Demonstration of d-AO spherical σ aromaticity in the Ce6O8 cluster.
  • Explanation of the cluster's exotic geometry and stability through the identified aromaticity.

Conclusions:

  • The bare Ce6O8 cluster exhibits a previously unreported form of d-AO spherical σ aromaticity.
  • This aromaticity is key to understanding the cluster's unique structure and stability.
  • Ce6O8 complexes are important in various reactions and exist in diverse forms, acting as oxidizing agents.