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Aziridine is an organic compound consisting of the three-membered
heterocycle A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and ...
. It is a colorless, toxic, volatile liquid that is of significant practical interest. Aziridine was discovered in 1888 by the chemist
Siegmund Gabriel Siegmund Gabriel (7 November 1851 – 22 March 1924) was a German chemist. Scientific career Siegmund Gabriel began studying chemistry at the University of Berlin in 1871. He continued his studies at the University of Heidelberg in 1872 wi ...
. Its derivatives, also referred to as
aziridines 220 px, chemotherapeutic agent by virtue of its antitumour activity.">chemotherapy.html" ;"title="Mitomycin C, an aziridine, is used as a chemotherapy">chemotherapeutic agent by virtue of its antitumour activity. Aziridines are organic compound ...
, are of broader interest in medicinal chemistry.


Structure

The
bond angle Bond or bonds may refer to: Common meanings * Bond (finance), a type of debt security * Bail bond, a commercial third-party guarantor of surety bonds in the United States * Chemical bond, the attraction of atoms, ions or molecules to form chemical ...
s in aziridine are approximately 60°, considerably less than the normal hydrocarbon bond angle of 109.5°, which results in
angle strain In organic chemistry, ring strain is a type of instability that exists when bonds in a molecule form angles that are abnormal. Strain is most commonly discussed for small rings such as cyclopropanes and cyclobutanes, whose internal angles are s ...
as in the comparable
cyclopropane Cyclopropane is the cycloalkane with the molecular formula (CH2)3, consisting of three methylene groups (CH2) linked to each other to form a ring. The small size of the ring creates substantial ring strain in the structure. Cyclopropane itself i ...
and
ethylene oxide Ethylene oxide is an organic compound with the formula . It is a cyclic ether and the simplest epoxide: a three-membered ring consisting of one oxygen atom and two carbon atoms. Ethylene oxide is a colorless and flammable gas with a faintly sw ...
molecules. A
banana bond In organic chemistry, a bent bond, also known as a banana bond, is a type of covalent chemical bond with a geometry somewhat reminiscent of a banana. The term itself is a general representation of electron density or configuration resembling a ...
model explains bonding in such compounds. Aziridine is less
basic BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages designed for ease of use. The original version was created by John G. Kemeny and Thomas E. Kurtz at Dartmouth College i ...
than acyclic
aliphatic In organic chemistry, hydrocarbons ( compounds composed solely of carbon and hydrogen) are divided into two classes: aromatic compounds and aliphatic compounds (; G. ''aleiphar'', fat, oil). Aliphatic compounds can be saturated, like hexane ...
amines, with a
pKa PKA may refer to: * Professionally known as: ** Pen name ** Stage persona * p''K''a, the symbol for the acid dissociation constant at logarithmic scale * Protein kinase A, a class of cAMP-dependent enzymes * Pi Kappa Alpha, the North-American so ...
of 7.9 for the
conjugate acid A conjugate acid, within the Brønsted–Lowry acid–base theory, is a chemical compound formed when an acid donates a proton () to a base—in other words, it is a base with a hydrogen ion added to it, as in the reverse reaction it loses a ...
, due to increased s character of the nitrogen free electron pair.
Angle strain In organic chemistry, ring strain is a type of instability that exists when bonds in a molecule form angles that are abnormal. Strain is most commonly discussed for small rings such as cyclopropanes and cyclobutanes, whose internal angles are s ...
in aziridine also increases the barrier to
nitrogen inversion In chemistry, pyramidal inversion (also umbrella inversion) is a fluxional process in compounds with a pyramidal molecule, such as ammonia (NH3) "turns inside out". It is a rapid oscillation of the atom and substituents, the molecule or ion pass ...
. This barrier height permits the isolation of separate ''invertomers'', for example the ''cis'' and ''trans'' invertomers of ''N''-chloro-2-methylaziridine.


Synthesis and uses

Aziridine is produced industrially from
aminoethanol Aminoethanol may refer to: * 1-Aminoethanol * Ethanolamine Ethanolamine (2-aminoethanol, monoethanolamine, ETA, or MEA) is an organic chemical compound with the formula or . The molecule is bifunctional, containing both a primary amine and a ...
via two related routes. The Nippon Shokubai process requires an oxide catalyst and high temperatures to effect the dehydration. In the
Wenker synthesis The Wenker synthesis is an organic reaction converting a beta amino alcohol to an aziridine with the help of sulfuric acid. It is used industrially for the synthesis of aziridine itself. The original Wenker synthesis of aziridine itself takes ...
, the aminoethanol is converted to the sulfate ester, which undergoes base-induced sulfate elimination. Older methods entailed amination of 1,2-dichloroethane and cyclization of 2-chloroethylamine. Aziridine forms a wide variety of polymeric derivatives, known as
polyethylenimine Polyethylenimine (PEI) or polyaziridine is a polymer with repeating units composed of the amine group and two carbon aliphatic ''CHCH'' spacers. Linear polyethyleneimines contain all secondary amines, in contrast to branched PEIs which contain pr ...
s (PEI). These and related species are useful
crosslinking agent In chemistry and biology a cross-link is a bond or a short sequence of bonds that links one polymer chain to another. These links may take the form of covalent bonds or ionic bonds and the polymers can be either synthetic polymers or natural ...
s and precursors for coatings.


Safety

Aziridine is highly toxic with an LD50 of 14 mg (oral, rats). It is a skin irritant. As an
alkylating agent Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effectin ...
, it is also a mutagen. It is reactive toward DNA, potentially relevant to its mutagenicity. Aziridine containing compounds also appear to be similarly dangerous.


See also

* Binary ethylenimine, a dimeric form of aziridine


References

{{Commonscat Functional groups IARC Group 2B carcinogens Aziridines