Stereochemistry, a subdiscipline of chemistry
Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....

, involves the study of the relative spatial arrangement of atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...

s within molecule
A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...

s. An important branch of stereochemistry is the study of chiral
Chirality (chemistry)
A chiral molecule is a type of molecule that lacks an internal plane of symmetry and thus has a non-superimposable mirror image. The feature that is most often the cause of chirality in molecules is the presence of an asymmetric carbon atom....


Stereochemistry is also known as 3D
Three-dimensional space
Three-dimensional space is a geometric 3-parameters model of the physical universe in which we live. These three dimensions are commonly called length, width, and depth , although any three directions can be chosen, provided that they do not lie in the same plane.In physics and mathematics, a...

 chemistry because the prefix "stereo-" means "three-dimensionality".

The study of stereochemical problems spans the entire range of organic
Organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...

, inorganic
Inorganic chemistry
Inorganic chemistry is the branch of chemistry concerned with the properties and behavior of inorganic compounds. This field covers all chemical compounds except the myriad organic compounds , which are the subjects of organic chemistry...

, biological
Biochemistry, sometimes called biological chemistry, is the study of chemical processes in living organisms, including, but not limited to, living matter. Biochemistry governs all living organisms and living processes...

, physical
Physical chemistry
Physical chemistry is the study of macroscopic, atomic, subatomic, and particulate phenomena in chemical systems in terms of physical laws and concepts...

 and supramolecular
Supramolecular chemistry
Supramolecular chemistry refers to the area of chemistry beyond the molecules and focuses on the chemical systems made up of a discrete number of assembled molecular subunits or components...

 chemistries. Stereochemistry includes methods for determining and describing these relationships; the effect on the physical
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...

 or biological
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...

 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
Dynamic stereochemistry
In chemistry, dynamic stereochemistry studies the effect of stereochemistry on the reaction rate of a chemical reaction. Stereochemistry is involved in:* stereospecific reactions* stereoselective or asymmetric reactions* racemisation processes-References:...


History and significance

Louis Pasteur
Louis Pasteur
Louis Pasteur was a French chemist and microbiologist born in Dole. He is remembered for his remarkable breakthroughs in the causes and preventions of diseases. His discoveries reduced mortality from puerperal fever, and he created the first vaccine for rabies and anthrax. His experiments...

 could rightly be described as the first stereochemist, having observed in 1849 that salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...

s of tartaric acid
Tartaric acid
Tartaric acid is a white crystalline diprotic organic acid. It occurs naturally in many plants, particularly grapes, bananas, and tamarinds; is commonly combined with baking soda to function as a leavening agent in recipes, and is one of the main acids found in wine. It is added to other foods to...

 collected from wine
Wine is an alcoholic beverage, made of fermented fruit juice, usually from grapes. The natural chemical balance of grapes lets them ferment without the addition of sugars, acids, enzymes, or other nutrients. Grape wine is produced by fermenting crushed grapes using various types of yeast. Yeast...

 production 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 Hoff
Jacobus Henricus van 't Hoff
Jacobus Henricus van 't Hoff, Jr. was a Dutch physical and organic chemist and the first winner of the Nobel Prize in chemistry. He is best known for his discoveries in chemical kinetics, chemical equilibrium, osmotic pressure, and stereochemistry...

 and Joseph Le Bel explained optical activity in terms of the tetrahedral arrangement of the atoms bound to carbon.

An infamous demonstration of the significance of stereochemistry was the thalidomide
Thalidomide was introduced as a sedative drug in the late 1950s that was typically used to cure morning sickness. In 1961, it was withdrawn due to teratogenicity and neuropathy. There is now a growing clinical interest in thalidomide, and it is introduced as an immunomodulatory agent used...

 disaster. Thalidomide is a drug
A pharmaceutical drug, also referred to as medicine, medication or medicament, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease.- Classification :...

, first prepared in 1957 in Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

, prescribed for treating morning sickness in pregnant
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...

 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
Teratology is the study of abnormalities of physiological development. It is often thought of as the study of human birth defects, but it is much broader than that, taking in other non-birth developmental stages, including puberty; and other non-human life forms, including plants.- Etymology :The...

 effects, causing serious genetic
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

 damage to early embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

nic growth and development. In the human body, thalidomide undergoes racemization
In chemistry, racemization refers to the converting of an enantiomerically pure mixture into a mixture where more than one of the enantiomers are present...

: even if only one of the two stereoisomers is ingested, the other one is produced. Thalidomide is currently used as a treatment for leprosy
Leprosy or Hansen's disease is a chronic disease caused by the bacteria Mycobacterium leprae and Mycobacterium lepromatosis. Named after physician Gerhard Armauer Hansen, leprosy is primarily a granulomatous disease of the peripheral nerves and mucosa of the upper respiratory tract; skin lesions...

 and 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 projection
Fischer projection
The Fischer projection, devised by Hermann Emil Fischer in 1891, is a two-dimensional representation of a three-dimensional organic molecule by projection. Fischer projections were originally proposed for the depiction of carbohydrates and used by chemists, particularly in organic chemistry and...

 is a simplified way to depict the stereochemistry around a stereocenter.


Many definitions that describe a specific conformation (IUPAC Gold Book) exist:
  • a torsion angle of ±60° is called gauche
  • a torsion angle between 0° and ± 90° is called syn (s)
  • a torsion angle between ± 90° and 180° is called anti (a)
  • a torsion angle between 30° and 150° or between –30° and –150° is called clinal
  • a torsion angle between 0° and 30° or 150° and 180° is called periplanar (p)
  • a torsion angle between 0° to 30° is called synperiplanar or syn- or cis-conformation (sp)
  • a torsion angle between 30° to 90° and –30° to –90° is called synclinal or gauche or skew (sc)
  • a torsion angle between 90° to 150°, and –90° to –150° is called anticlinal (ac)
  • a torsion angle between ± 150° to 180° is called antiperiplanar or anti or trans (ap).

Torsional strain results from resistance to twisting about a bond.


  • Atropisomerism
  • Cis-trans isomerism
  • Conformational isomerism
    Conformational isomerism
    In chemistry, conformational isomerism is a form of stereoisomerism in which the isomers can be interconverted exclusively by rotations about formally single bonds...

  • Diastereomers
  • Enantiomers
  • Rotamers
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