Related Experiment Video

Updated: Jun 23, 2026

Measurements of Long-range Electronic Correlations During Femtosecond Diffraction Experiments Performed on Nanocrystals of Buckminsterfullerene
08:44

Measurements of Long-range Electronic Correlations During Femtosecond Diffraction Experiments Performed on Nanocrystals of Buckminsterfullerene

Published on: August 22, 2017

Intermolecular interaction-controlled tuning of the two-photon absorption of fullerene bound in a buckycatcher

Swapan Chakrabarti, Kenneth Ruud

    The Journal of Physical Chemistry. A
    |May 8, 2009
    PubMed

    More Related Videos

    Synthesis and Characterization of Supramolecular Colloids09:26

    Synthesis and Characterization of Supramolecular Colloids

    Published on: April 22, 2016

    Probing C84-embedded Si Substrate Using Scanning Probe Microscopy and Molecular Dynamics13:58

    Probing C84-embedded Si Substrate Using Scanning Probe Microscopy and Molecular Dynamics

    Published on: September 28, 2016

    Related Concept Videos

    Photochemical Electrocyclic Reactions: Stereochemistry01:26

    Photochemical Electrocyclic Reactions: Stereochemistry

    The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
    Selection Rules: Photochemical Activation
    ¹H NMR: Long-Range Coupling01:27

    ¹H NMR: Long-Range Coupling

    The coupling interactions of nuclei across four or more bonds are usually weak, with J values less than 1 Hz. While these are usually not observed in spectra, the presence of multiple bonds along the coupling pathway can result in observable long-range coupling.
    In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene π orbitals.
    Cycloaddition Reactions: MO Requirements for Thermal Activation01:16

    Cycloaddition Reactions: MO Requirements for Thermal Activation

    Thermal cycloadditions are reactions where the source of activation energy needed to initiate the reaction is provided in the form of heat. A typical example of a thermally-allowed cycloaddition is the Diels–Alder reaction, which is a [4 + 2] cycloaddition. In contrast, a [2 + 2] cycloaddition is thermally forbidden.
    Spin–Spin Coupling Constant: Overview01:08

    Spin–Spin Coupling Constant: Overview

    In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
    Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must have a...
    Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)01:22

    Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)

    Vicinal or three-bond coupling is commonly observed between protons attached to adjacent carbons. Here, nuclear spin information is primarily transferred via electron spin interactions between adjacent C‑H bond orbitals. This generally favors the antiparallel arrangement of spins, so 3J values are usually positive.
    The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the involved orbitals. The...
    Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)01:20

    Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)

    Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
    The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...