Stereochemistry, a subdiscipline of
chemistry, involves the study of the relative spatial arrangement of atoms within molecules. An important branch of stereochemistry is the study of chiral molecules [JerryMarch] .
Stereochemistry includes methods for determining and describing these relationships; the effect on the physical or biological properties these relationships impart upon the molecules in question, and the manner in which these relationships influence the reactivity of the molecules in question (
dynamic stereochemistry). Louis Pasteurcould rightly be described as the first stereochemist, having observed in 1849that salts of tartaric acidcollected from wineproduction vessels could rotate plane polarized light, but that salts from other sources did not. This property, the only physical property in which the two types of tartrate salts differed, is due to optical isomerism. In 1874, Jacobus Henricus van 't Hoffand Joseph Le Belexplained optical activity in terms of the tetrahedral arrangement of the atoms bound to carbon.
One of the most infamous demonstrations of the significance of stereochemistry was the
thalidomidedisaster. Thalidomide is a drug, first prepared in 1957in Germany, prescribed for treating morning sickness in pregnant women. The drug however was discovered to cause deformation in babies. It was discovered that one optical isomer of the drug was safe while the other had teratogenic effects, causing serious genetic damage to early embryonic growth and development. In the human body, thalidomide undergoes racemization: even if only one of the two stereoisomers is ingested, the other one is produced. Thalidomide is currently used as a treatment for leprosyand must be used with contraceptives in women to prevent pregnancy-related deformations.This disaster was a driving force behind requiring strict testing of drugs before making them available to the public.
Cahn-Ingold-Prelog priority rules are part of a system for describing a molecule's stereochemistry. They rank the atoms around a stereocenter in a standard way, allowing the relative position of these atoms in the molecule to be described unambiguously. A
Fischer projectionis a simplified way to depict the stereochemistry around a stereocenter.
* "Cis"-"trans" isomerism
* [http://www.chm.bris.ac.uk/motm/thalidomide/first.html Information on Thalidomide]
* [http://microscopy.fsu.edu/featuredmicroscopist/modderman/galleryindex.html Polarized photomicrographs of crystalline chemicals with descriptions and uses, including tartaric acid]
Wikimedia Foundation. 2010.