Chemical structure

The chemical structure reflects the structure on the molecular or ionic level of a uniform ( homogeneous ) substance. It indicates how atoms, atom groups, ions and bonds or free electron pairs are spatially arranged. It thus provides more information than the sum formula or one of the different spellings. In detail, the constitution , configuration and conformation describe the structure of molecular compounds and a crystal lattice describes the structure of ionic compounds. Various chemical formulas and models, such as spherical or ball-and-stick models , are used to represent them. Information about the structure of a compound is often included in its name , according to the rules of chemical nomenclature . Modern databases, on the other hand, work with clear structure codes such as InChI , SMILES or WLN . Structural chemistry deals with the elucidation of the chemical structure .

Instrumental procedures

The structure analysis of molecules is carried out in structural analysis with various instrumental methods.

• The structure of crystalline substances can mainly be determined using diffraction methods. Depending on whether X-ray, electron or neutron beams are diffracted, these are the methods
  • X-ray diffraction or X-ray diffraction
  • Electron diffraction and
  • Neutron diffraction
• The methods are suitable for determining the structure in liquids, gases and amorphous solids
  • NMR spectroscopy

• • Mass spectrometry
  • Vibrational spectroscopy , especially infrared and Raman spectroscopy
  • UV spectroscopy
  • the X-ray absorption spectroscopy , especially the EXAFS spectroscopy , the z. B. allows the determination of the distance from neighboring atoms.
• Some methods are mainly used to determine the chemical composition of surfaces. But they can also be used to investigate solid structures:
  • X-ray Photoelectron Spectroscopy (XPS) and
  • Auger Electron Spectroscopy (AES).

Historical

The term "chemical structure" was introduced in 1861 by Alexander Butlerow . He wrote: "... I would like [...] to designate the way in which the atoms are bonded to one another in a composite body by the name of the chemical structure." In the Soviet Union , Butlerov's contribution was considered crucial for the understanding of organic chemistry, and Butlerov as the founder of scientific organic chemistry.

Individual evidence

1. ↑ Harald Günther: NMR spectroscopy , 3rd edition, Thieme Verlag, Stuttgart, 1992, 520 pages, ISBN 3-13-487503-9 .
2. ^ Dudley H. Williams, Ian Fleming: Spectroscopic methods in organic chemistry , 2nd edition (1971), Thieme Verlag, Stuttgart, ISBN 313 437202 9 , pp. 80-140.
3. ^ Dudley H. Williams, Ian Fleming: Spectroscopic methods in organic chemistry , 2nd edition (1971), Thieme Verlag, Stuttgart, ISBN 313-437202-9 , pp. 141-186.
4. ^ Dudley H. Williams, Ian Fleming: Spectroscopic methods in organic chemistry , 2nd edition (1971), Thieme Verlag, Stuttgart, ISBN 313-437202-9 , pp. 41-79.
5. ^ Dudley H. Williams, Ian Fleming: Spectroscopic methods in organic chemistry , 2nd edition (1971), Thieme Verlag, Stuttgart, ISBN 313-437202-9 , pp. 6-40.
6. ↑ Alexander Butlerov: Something about the chemical structure of the body. In: Emil Erlenmeyer (Hrsg.): Journal for Chemistry and Pharmacy . tape 4 . Ferdinand Enke, 1861, ISSN  0258-1620 , p. 549–560 ( online on the pages of the Bayerische Staatsbibliothek BSB Munich - limited preview in the Google book search).
7. ^ David E. Lewis, Early Russian Organic Chemists and Their Legacy . Springer, Heidelberg, New York, Dordrecht, London 2012, ISBN 978-3-642-28218-8 , pp. 32 , doi : 10.1007 / 978-3-642-28219-5_2 ( springer.com [accessed on January 22, 2018] limited preview in the Google book search).