Introduction into the
Symmetry of Molecules

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Spectroscopic Tools

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You assume determined things (articles, pictures) quite unconsciously in the daily life as more or less regular in their form, with more or less pleasant proportions, see in them a harmonious arrangement or a periodic repetition of their structural components. They feel it as more or less symmetrical. The term " symmetry '' and its mathematical application is for the natural sciences an important aid to the simplification and qualitative assertion of many problems.
In chemistry views of symmetry attained rising meaning in the last years. Particularly with the investigation of the structure of the subject one of the most urgent questions is after the spatial relations of the atoms in a molecule or the molecules in a crystal.
Typical problem definitions in the chemistry, for whose solution views of symmetry are consulted, are:

  • the optical activity -- a prerequisite for occurring optically active molecules and crystals is the absence of certain symmetry characteristics
  • the spectroscopy -- occurring or being missing lines or gangs in the spectra depend on the symmetry of the combining statuses
  • the quantum chemistry -- the atomic and molecule orbital indicate certain symmetries. Quantum-chemical calculations can be considerably simplified by views of symmetry
  • the dipole moments -- in symmetrically arranged molecules individual linkage moments can compensate themselves mutually, so that occurring or not occuring of dipole moments and their direction from views of symmetry can be derived
  • the crystal analysis -- the symmetry of the crystals determines the occurring x-ray diffractions.
Besides views of symmetry play alos a important role, for the decision of relatively simple questions like a detecting of the number of isomeric compounds.
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