Jove
Visualize
Contact Us
JoVE
x logofacebook logolinkedin logoyoutube logo
ABOUT JoVE
OverviewLeadershipBlogJoVE Help Center
AUTHORS
Publishing ProcessEditorial BoardScope & PoliciesPeer ReviewFAQSubmit
LIBRARIANS
TestimonialsSubscriptionsAccessResourcesLibrary Advisory BoardFAQ
RESEARCH
JoVE JournalMethods CollectionsJoVE Encyclopedia of ExperimentsArchive
EDUCATION
JoVE CoreJoVE BusinessJoVE Science EducationJoVE Lab ManualFaculty Resource CenterFaculty Site
Terms & Conditions of Use
Privacy Policy
Policies

Related Concept Videos

Aromatic Hydrocarbon Cations: Structural Overview01:18

Aromatic Hydrocarbon Cations: Structural Overview

2.7K
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...
2.7K
Criteria for Aromaticity and the Hückel 4n + 2 Rule01:20

Criteria for Aromaticity and the Hückel 4n + 2 Rule

10.1K
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...
10.1K
Aromatic Hydrocarbon Anions: Structural Overview01:18

Aromatic Hydrocarbon Anions: Structural Overview

2.6K
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...
2.6K
Frost Circles for Different Conjugated Systems01:18

Frost Circles for Different Conjugated Systems

2.6K
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.
2.6K
π Electron Effects on Chemical Shift: Aromatic and Antiaromatic Compounds01:14

π Electron Effects on Chemical Shift: Aromatic and Antiaromatic Compounds

1.2K
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...
1.2K
Five-Membered Heterocyclic Aromatic Compounds: Overview01:13

Five-Membered Heterocyclic Aromatic Compounds: Overview

3.7K
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,...
3.7K

You might also read

Related Articles

Articles linked to this work by shared authors, journal, and citation graph.

Sort by
Same author

[<sup>1</sup>H]/[<sup>2</sup>H] discriminated bianthryl atropisotopomers: enantiospecific syntheses from BINOL and direct multi-spectroscopic analyses of their isotopic chirality.

Chemical science·2026
Same author

Rh-Catalyzed Cycloaddition Cascade of Allenynes and Maleimides: A Powerful Strategy for Constructing Complex Pentacyclic Structures with a Bicyclo[2.2.2]octene Core.

Organic letters·2025
Same author

Kinetics of the Reactions CO<sub>2</sub> + O ⇆ CO + O<sub>2</sub>.

The journal of physical chemistry. A·2025
Same author

Singlet and Triplet Electronic States Involved in the Reactions CO<sub>2</sub> + O → CO<sub>3</sub> → CO + O<sub>2</sub>.

The journal of physical chemistry. A·2025
Same author

Formation of Substituted Benzocyclobutenes Starting from Donor-Acceptor Cyclopropanes.

The Journal of organic chemistry·2025
Same author

Competing pathways to aromaticity governed by amine dehydrogenation and metal-organic complexation in on-surface synthesis.

Chemical science·2025

Related Experiment Video

Updated: Jun 1, 2025

Preparation of a Corannulene-functionalized Hexahelicene by CopperI-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units
09:35

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

Published on: September 18, 2016

11.4K

Ground and Excited State Aromaticity in Azulene-Based Helicenes.

Amisadai Lorenzo Reyes1, Fatim Ndeye Ndiaye1, Albert Artigas2

  • 1Aix Marseille Univ, CNRS, Centrale Med, iSm2, Marseille, France.

Chemphyschem : a European Journal of Chemical Physics and Physical Chemistry
|January 20, 2025
PubMed
Summary

Azulene-containing helicenes exhibit charge separation in their ground state, which vanishes in the excited triplet state. Unexpected aromatic delocalization circuits appear in larger helicenes, revealing novel electronic properties.

Keywords:
aromaticityazuleneexcited statesnon-benzenoid hydrocarbonspolycyclic aromatic hydrocarbons

More Related Videos

Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles
11:45

Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles

Published on: August 22, 2018

8.4K
Preparation of Enantiopure Non-Activated Aziridines and Synthesis of Biemamide B, D, and epiallo-Isomuscarine
11:04

Preparation of Enantiopure Non-Activated Aziridines and Synthesis of Biemamide B, D, and epiallo-Isomuscarine

Published on: June 13, 2022

2.9K

Related Experiment Videos

Last Updated: Jun 1, 2025

Preparation of a Corannulene-functionalized Hexahelicene by CopperI-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units
09:35

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

Published on: September 18, 2016

11.4K
Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles
11:45

Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles

Published on: August 22, 2018

8.4K
Preparation of Enantiopure Non-Activated Aziridines and Synthesis of Biemamide B, D, and epiallo-Isomuscarine
11:04

Preparation of Enantiopure Non-Activated Aziridines and Synthesis of Biemamide B, D, and epiallo-Isomuscarine

Published on: June 13, 2022

2.9K

Area of Science:

  • Organic Chemistry
  • Quantum Chemistry
  • Materials Science

Background:

  • Helicenes are polycyclic aromatic hydrocarbons with a helical structure.
  • Azulene is a non-alternant aromatic hydrocarbon isomer of naphthalene.
  • Understanding electron delocalization is crucial for designing novel organic materials.

Purpose of the Study:

  • To investigate electron delocalization in ground and excited states of azulene-containing helicenes.
  • To explore the relationship between molecular size and aromaticity in these systems.
  • To rationalize the observed electronic properties using advanced computational methods.

Main Methods:

  • Synthesis of azulene-containing helicenes.
  • Calculation of magnetically induced properties (IMS3D and ACID).
  • Electron density decomposition analysis (EDDB) and wavefunction decomposition.

Main Results:

  • Azulene-containing helicenes show ground-state charge separation absent in the triplet excited state.
  • Helicenes with more than six fused cycles exhibit unexpected aromatic delocalization circuits.
  • Wavefunction decomposition explains the emergence of these delocalization pathways.

Conclusions:

  • Azulene incorporation into helicenes leads to unique electronic behaviors.
  • Molecular size significantly influences aromaticity and electron delocalization in helicenes.
  • The study provides insights into the fundamental electronic structure of complex polycyclic systems.