Related Experiment Video
Updated: May 28, 2025

Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
Orbital contributions to the magnetic shielding of cyclo[2n]carbons (n = 3-12)
1University of Belgrade - Faculty of Chemistry, Studentski trg 12-16, P.O. Box 158, 11000 Belgrade, Serbia. mbaranac@chem.bg.ac.rs.
Abstract:
Natural chemical shielding (NCS) analysis yields erroneous magnetic shielding values (or NICS, which is the negative of magnetic shielding) for the core, σ and in-plane π orbitals of cyclo[2n]carbons (n = 3-12), assuming that the external magnetic field acts perpendicular to the ring plane. The most diagnostic are the unphysically large contributions of core electrons to the shielding inside the rings. An alternative way to estimate the contribution of the in-plane π-system to shielding values is proposed and is based on the addition of a hydrogen atom outside each carbon atom in the plane of the cyclo[2n]carbon ring, while keeping its geometry intact. The πin contributions are then estimated as the difference between the total shielding values of cyclo[2n]carbon and the total shielding values of a ring with added Hs. This, however, includes the C-H bond effects near the carbon framework.
More Related Videos
09:35Preparation of a Corannulene-functionalized Hexahelicene by CopperI-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units
Published on: September 18, 2016
09:45Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene
Published on: March 20, 2017
Related Concept Videos
Frost Circles for Different Conjugated Systems
Aromatic Hydrocarbon Anions: Structural Overview
Due to the absence of continuous...
Diamagnetic Shielding of Nuclei: Local Diamagnetic Current
The Energies of Atomic Orbitals
π Electron Effects on Chemical Shift: Overview
π Electron Effects on Chemical Shift: Aromatic and Antiaromatic Compounds