Publication

Long-Range Bonding/Nonbonding Interactions: A Donor Acceptor Resonance Studied by Dynamic NMR

2015
Journal Articles

Abstract

Long-range bonding interactions were evaluated using variable-temperature NMR spectroscopy and suitable 2'-CH2X-substituted phenylpyridines (X = Me, NMe2, OMe, F). It was found that the arylpyridyl rotational barriers were lower when electronegative atoms were bound to the alpha carbon of the 2' moiety. This effect was ascribed to a stabilizing interaction in the transition state due to the lone pair of the heterocyclic nitrogen with the alpha carbon. Computational support for this hypothesis came from CCSD(T)/6-31+G(d) calculations. Steric effects of the X moiety were ruled out by comparison of the rotational barriers of analogous biphenyls.

Official source

https://infoscience.epfl.ch/entities/publication/e69a7a87-220c-4da6-9d40-22d89fd54a17

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2015
Journal Articles

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/e69a7a87-220c-4da6-9d40-22d89fd54a17

About this result

Related concepts (32)

Lone pair

In chemistry, a lone pair refers to a pair of valence electrons that are not shared with another atom in a covalent bond and is sometimes called an unshared pair or non-bonding pair. Lone pairs are found in the outermost electron shell of atoms. They can be identified by using a Lewis structure. Electron pairs are therefore considered lone pairs if two electrons are paired but are not used in chemical bonding. Thus, the number of electrons in lone pairs plus the number of electrons in bonds equals the number of valence electrons around an atom.

VSEPR theory

Valence shell electron pair repulsion (VSEPR) theory (ˈvɛspər,_vəˈsɛpər , ), is a model used in chemistry to predict the geometry of individual molecules from the number of electron pairs surrounding their central atoms. It is also named the Gillespie-Nyholm theory after its two main developers, Ronald Gillespie and Ronald Nyholm. The premise of VSEPR is that the valence electron pairs surrounding an atom tend to repel each other. The greater the repulsion, the higher in energy (less stable) the molecule is.

Electronegativity

Electronegativity, symbolized as χ, is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the distance at which its valence electrons reside from the charged nucleus. The higher the associated electronegativity, the more an atom or a substituent group attracts electrons.

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