London force

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London forces between non-polar 2-atomic molecules: A spontaneous quantum mechanical fluctuation creates a small polarization (negative charge δ- on the far left of the molecule in blue, positive charge δ + on the right on the same molecule in red). The electrons in the neighboring molecule are polarized in the same way, etc. The result is an attraction with macroscopic effects.

London forces (after the physicist Fritz London ; in literature also called London force , London dispersion or attractive van der Waals bond ) are weak forces of attraction between polar or non-polar molecules and atoms , which are caused by spontaneous polarization of a particle and this creates induced dipoles in neighboring particles. In quantum mechanics , such interactions can be modeled as a force field that decreases with the sixth power of the distance:

The London Forces explain the existence of liquid and solid aggregate states of non-polar compounds, which should not exist if one only considers the repulsive interaction of their electron shells (in the absence of other intermolecular interactions such as hydrogen bonds ) . The London forces between non-polar, uncharged particles are much weaker than the other types of bond . In computational chemistry , they are difficult to describe and parameterize. The shares of London's dispersion forces in the forces of attraction between polar molecules are usually stronger than the contributions of the dipole-dipole interaction . Together with Debye 's forces (interaction between permanent dipole molecules and non-polar particles), these belong to the van der Waals interactions .

Individual evidence

  1. ^ R. Eisenschitz and F. London, Z. Physik 60 , 491 (1930), DOI: 10.1007 / BF01341258 .
  2. ↑ F. London, Z. Physik 63 , 245 (1930), DOI: 10.1007 / bf01421741 and Z. Physik. Chemistry, B11 , 222 (1930)
  3. ↑ TL Brown, HE LeMay, BE Bursten, Chemistry - The Central Science, 10th Edition, Pearson Studium, Munich, Boston, 2007, p. 519.
  4. ↑ TL Brown, HE LeMay, BE Bursten, Chemistry - The Central Science, 10th Edition, Pearson Studium, Munich, Boston, 2007, p. 519.