In chemistry

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....

, a nitrogen

Nitrogen

Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

 compound like ammonia

Ammonia

Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

 in a trigonal pyramid

Trigonal pyramid (chemistry)

In chemistry, a trigonal pyramid is a molecular geometry with one atom at the apex and three atoms at the corners of a trigonal base. When all three atoms at the corners are identical, the molecule belongs to point group C3v. One example of a molecule with a trigonal pyramidal geometry is ammonia...

 geometry undergoes rapid nitrogen inversion whereby the molecule

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...

 turns inside out. This interconversion is a room temperature

Temperature

Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

 process because the energy barrier (24.2 kJ/mol) is relatively small. Contrast this to phosphine

Phosphine

Phosphine is the compound with the chemical formula PH3. It is a colorless, flammable, toxic gas. Pure phosphine is odourless, but technical grade samples have a highly unpleasant odor like garlic or rotting fish, due to the presence of substituted phosphine and diphosphine...

 which does not show inversion at room temperature (energy barrier: 132 kJ/mol) . Even if all three substituents on the nitrogen in an amine

Amine

Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines,...

 are different, rapid inversion would prevent the nitrogen atom

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...

 from becoming a permanent 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....

 center, since such inversion becomes effectively like a conformational change.

However, if the nitrogen is a bridgehead atom in a bicyclo or a similar compound where it cannot invert around the lone electron pair, then the nitrogen atom could be a chiral center if all three substituents on it are effectively different. An example of such a compound is Tröger's base

Tröger's base

Tröger's base is an organic compound that exhibits chirality due to the presence of two bridgehead stereogenic nitrogen atoms in its structure. The compound was first synthesised in 1887 from p-toluidine and formaldehyde in acid solution by Julius Tröger. It took until 1935 for the elucidation of...

.

In one study the inversion in an aziridine

Aziridine

Aziridines are organic compounds containing the aziridine functional group, a three-membered heterocycle with one amine group and two methylene groups...

 was slowed down by a factor of 50 by placing the nitrogen atom in the vicinity of a phenol

Phenol

Phenol, also known as carbolic acid, phenic acid, is an organic compound with the chemical formula C6H5OH. It is a white crystalline solid. The molecule consists of a phenyl , bonded to a hydroxyl group. It is produced on a large scale as a precursor to many materials and useful compounds...

ic alcohol group compared to the oxidized hydroquinone

Hydroquinone

Hydroquinone, also benzene-1,4-diol or quinol, is an aromatic organic compound that is a type of phenol, having the chemical formula C6H42. Its chemical structure, shown in the table at right, has two hydroxyl groups bonded to a benzene ring in a para position. It is a white granular solid...

  :

The system interconverts by oxidation by oxygen

Oxygen

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 and reduction by sodium dithionite

Sodium dithionite

Sodium dithionite is a white crystalline powder with a weak sulfurous odor. It is a sodium salt of dithionous acid. Although it is stable under most conditions, it will decompose in hot water and in acid solutions...

.