Lecture

Aromaticity: Energetic Evaluations

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In course

CH-431: Physical and computational organic chemistry

This course introduces modern computational electronic structure methods and their broad applications to organic chemistry. It also discusses physical organic concepts to illustrate the stability and reactivity of organic molecules. ...

Description

This lecture delves into the concept of aromaticity, exploring the energy profiles of various compounds and the resonance energies involved. It discusses the stability of aromatic compounds, the resonance energy versus aromatic stabilization energy, and the methods used to measure aromaticity, such as Nucleus-Independent Chemical Shifts (NICS) and magnetic criteria. The presentation also covers the multifaceted definition of aromaticity, quantifying antiaromaticity, and identifying aromatic molecules.

Instructor

Anne-Clémence Corminboeuf

Teaching & PhD PhD Students Liam Oliver Marsh, Pratham Pushparaj Deshmukh, Roel Christiaan M Raike, Thanapat Worakul, Osvaldo Hernandez Cuellar, Juliette Veronique Schleicher, Yannick Calvino Alonso, Sara Bassetta, Yuri Cho, Kelian Dietmar Marc Gaedecke, Guoyuan Liu Past EPFL PhD Students Fabrice Avaltroni, Daniel Filipe Jana, Stephan Niklaus Steinmann, Jérôme Florian Gonthier, Riccardo Petraglia, Antonio Prlj, Laurent Alexis Clément Vannay, Alberto Fabrizio, Kun-Han Lin, Boodsarin Sawatlon, Raimon Fabreg

Official source

Related concepts (32)

Aromatic ring current

An aromatic ring current is an effect observed in aromatic molecules such as benzene and naphthalene. If a magnetic field is directed perpendicular to the plane of the aromatic system, a ring current is induced in the delocalized π electrons of the aromatic ring. This is a direct consequence of Ampère's law; since the electrons involved are free to circulate, rather than being localized in bonds as they would be in most non-aromatic molecules, they respond much more strongly to the magnetic field.

Möbius aromaticity

In organic chemistry, Möbius aromaticity is a special type of aromaticity believed to exist in a number of organic molecules. In terms of molecular orbital theory these compounds have in common a monocyclic array of molecular orbitals in which there is an odd number of out-of-phase overlaps, the opposite pattern compared to the aromatic character to Hückel systems. The nodal plane of the orbitals, viewed as a ribbon, is a Möbius strip, rather than a cylinder, hence the name.

Organic chemistry

Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms. Study of structure determines their structural formula. Study of properties includes physical and chemical properties, and evaluation of chemical reactivity to understand their behavior.

Resonance

Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied periodic force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscillating force is applied at a resonant frequency of a dynamic system, the system will oscillate at a higher amplitude than when the same force is applied at other, non-resonant frequencies. Frequencies at which the response amplitude is a relative maximum are also known as resonant frequencies or resonance frequencies of the system.

Hückel's rule

In organic chemistry, Hückel's rule predicts that a planar ring molecule will have aromatic properties if it has 4n + 2 π electrons, where n is a non-negative integer. The quantum mechanical basis for its formulation was first worked out by physical chemist Erich Hückel in 1931. The succinct expression as the 4n + 2 rule has been attributed to W. v. E. Doering (1951), although several authors were using this form at around the same time.

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