résonance

Traductions

• anglais

  Date : 1983

  Définition

  In organic chemistry, this term denotes a mathematical concept based on quantum mechanical consideration (i.e., the wave functions of electrons), which expresses the true nature of certain compounds which cannot be accurately represented by any one valence-bond structure.

  Note :

  It was originally applied to aromatic compounds such as benzine, for which there are many possible approximate structures, none of which is completely satisfactory. The resonance concept indicates that the actual molecular structure lies somewhere between these various approximations but is not capable of objective representation. The same idea has been found useful in regard to inorganic molecules in which an electron pair bond is present. The term resonance hybrid denotes molecules to which this concept applies. It is important to indicate that such a molecule does not vibrate back and forth between two or more structures, and that these structures are neither isotopes nor mixtures: the resonance phenomenon is an idealized mathematical expression of the actual molecule of, say, benzene, which cannot be duplicated by any pictorial device.

  Termes :

  1. resonance
  2. mesomerism