Search research articles

ABOUT JoVE

Overview Leadership Blog JoVE Help Center

AUTHORS

Publishing Process Editorial Board Scope & Policies Peer Review FAQ Submit

LIBRARIANS

Testimonials Subscriptions Access Resources Library Advisory Board FAQ

RESEARCH

JoVE Journal Methods Collections JoVE Encyclopedia of Experiments Archive

EDUCATION

JoVE Core JoVE Business JoVE Science Education JoVE Lab Manual Faculty Resource Center Faculty Site

Terms & Conditions of Use

Related Concept Videos

Molecular Orbital Theory II

Molecular Orbital Theory II

Molecular Orbital Energy Diagrams

Aromatic Hydrocarbon Anions: Structural Overview

Aromatic Hydrocarbon Anions: Structural Overview

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 overlap of p...

NMR Spectroscopy of Benzene Derivatives

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...

π Electron Effects on Chemical Shift: Overview

π Electron Effects on Chemical Shift: Overview

An applied magnetic field causes loosely bound π-electrons in organic molecules to circulate, producing a local or induced diamagnetic field over a large spatial volume. As the molecules tumble in solution, the field generated by π-electrons in spherical substituents results in a zero net field. However, the net field generated by π-electrons in non-spherical substituents is not zero. The effect of this induced field depends on the orientation of the molecule with respect to B0, resulting in...

π Electron Effects on Chemical Shift: Aromatic and Antiaromatic Compounds

π Electron Effects on Chemical Shift: Aromatic and Antiaromatic Compounds

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 annulenes. In...

IR Absorption Frequency: Delocalization

IR Absorption Frequency: Delocalization

Electron delocalization refers to the distribution of electrons across multiple atoms within a molecule rather than being confined to a single atom or bond. This phenomenon is common in systems with conjugated bonds—structures where alternating single and double bonds allow π-electrons to move freely across the network. The movement of electrons stabilizes the molecule and can affect various chemical properties, including vibrational frequencies observed in IR spectroscopy.
In IR spectroscopy,...

You might also read

Related Articles

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

Sort by

Same author

Hippocampo-supramammillary coupling across sleep and wake.

Scientific reports·2026

Same author

Luminescence Thermometry of a Nd<sup>III</sup> and Nd<sup>III</sup>/Yb<sup>III</sup> Imidazole Derived-Based MOFs: Thermally Enhanced Ytterbium Emission.

Chemistry, an Asian journal·2026

Same author

Hippocampal synchrony dynamically gates cortical connectivity across brain states.

Scientific reports·2026

Same author

Hydrodynamic cavitation-assisted acid pretreatment and fed-batch simultaneous saccharification and co-fermentation for ethanol production from sugarcane bagasse using immobilized cells of Scheffersomyces parashehatae.

Bioresource technology·2023

Same author

Physical and chemical characterization of drill cuttings: A review.

Marine pollution bulletin·2023

Same author

The role of microglia in 67NR mammary tumor-induced suppression of brain responses to immune challenges in female mice.

Journal of neurochemistry·2023

Search research articles

Related Experiment Video

Updated: May 17, 2026

Spatial Separation of Molecular Conformers and Clusters

Spatial Separation of Molecular Conformers and Clusters

Published on: January 9, 2014

Sigma-pi separation of the electron localization function and aromaticity.

J C Santos¹, W Tiznado, R Contreras

¹Departamento de Fisica, Facultad de Ciencias, Universidad de Chile, Casilla 653, Las Palmeras 3425, Nunoa, Santiago, Chile.

The Journal of Chemical Physics

|July 23, 2004

Summary

Researchers quantified molecular resonance using electron localization function (ELF) components. New ELFsigma and ELFpi analyses accurately describe aromaticity in various ring molecules, including novel compounds like Al4(2-).

More Related Videos

Site Directed Spin Labeling and EPR Spectroscopic Studies of Pentameric Ligand-Gated Ion Channels

Site Directed Spin Labeling and EPR Spectroscopic Studies of Pentameric Ligand-Gated Ion Channels

Published on: July 4, 2016

Polarization-Sensitive Two-Photon Microscopy for a Label-Free Amyloid Structural Characterization

Polarization-Sensitive Two-Photon Microscopy for a Label-Free Amyloid Structural Characterization

Published on: September 8, 2023

Related Experiment Videos

Last Updated: May 17, 2026

Spatial Separation of Molecular Conformers and Clusters

Spatial Separation of Molecular Conformers and Clusters

Published on: January 9, 2014

Site Directed Spin Labeling and EPR Spectroscopic Studies of Pentameric Ligand-Gated Ion Channels

Site Directed Spin Labeling and EPR Spectroscopic Studies of Pentameric Ligand-Gated Ion Channels

Published on: July 4, 2016

Polarization-Sensitive Two-Photon Microscopy for a Label-Free Amyloid Structural Characterization

Polarization-Sensitive Two-Photon Microscopy for a Label-Free Amyloid Structural Characterization

Published on: September 8, 2023

Area of Science:

Quantum Chemistry
Chemical Bonding Theory

Background:

The electron localization function (ELF) is a key tool for analyzing chemical bonding.
Quantifying molecular resonance and aromaticity remains an active area of research.

Purpose of the Study:

To separate the electron localization function (ELF) into its sigma and pi components.
To utilize topological analysis of ELFsigma and ELFpi for quantifying resonance.
To assess the aromaticity of classical and novel ring systems.

Main Methods:

Decomposition of the electron localization function (ELF) into sigma (ELFsigma) and pi (ELFpi) components.
Topological analysis of ELFsigma and ELFpi functions.
Examination of bifurcation values to characterize aromaticity.

Main Results:

Highest bifurcation values of ELFsigma and ELFpi correctly describe aromaticity in ring molecules.
Successfully characterized aromaticity in classical compounds and novel systems like B6CO6, Al4(2-), and N5-.
Identified significant sigma delocalization in Al4(2-), consistent with prior studies.

Conclusions:

The sigma-pi separation of ELF provides a robust method for quantifying resonance.
ELFsigma and ELFpi analyses offer valuable insights into the aromaticity of diverse chemical structures.
This approach validates and enhances the understanding of electronic delocalization in aromatic systems.