What Is Aziridine?
Aziridine is an organic compound with the chemical formula C2H5N.
It is also known as ethylene imine. The reaction of sodium hydroxide with β-aminoethyl sulfate yields aziridine. Industrially, aziridine can be produced from 1,2-dichloroethane and ammonia.
Aziridines share a common toxicity: they bind to nucleophiles, such as nucleobases in DNA, while opening the ring, leading to the mutagenicity of aziridines.
Uses of Aziridine
Aziridine is used in the manufacture of adhesives, fiber treatment agents, raw materials for polyethyleneimine, agricultural chemicals, and ion exchange resins. However, exposure of aziridine to skin and mucous membranes is highly toxic to the human body. Because of its toxic nature, it should be handled with care.
Aziridine compounds with aziridine groups are marketed as chemitites. This chemitite is used as a cross-linking agent in paints, adhesives, and coatings.
Properties of Aziridine
Aziridine has a melting point of -77.9°C and a boiling point of 55-56°C. It is a colorless, clear liquid. Aziridine has a characteristic ammonia-like odor.
Aziridine has an acid dissociation constant of 7.9 and is less basic than linear aliphatic amines.
Structure of Aziridine
Aziridine has a three-membered ring structure; it is a hetero three-membered ring compound consisting of one nitrogen atom and two carbon atoms. It has a molecular weight of 43.07 and a density of 0.8321 g/ml at 20°C.
Like cyclopropane and ethylene oxide, it is angularly strained. This is because the bond angle of the atoms in aziridine is approximately 60°, much smaller than the 109.5° that normal hydrocarbons have.
The bonding of these compounds can be explained using the banana bent bond model. That is, covalent bonds in the shape of a banana.
The bond angle of aziridine provides a high enough barrier to invert the nitrogen atom so that the trans and cis forms of N-chloro-2-methylaziridine can be separated.
Other Information on Aziridine
1. Synthesis of Aziridine
Aziridines can be synthesized from haloamines by intermolecular nucleophilic substitution reactions of halogens with adjacent amino groups. Similar reactions can proceed with amino alcohols if the hydroxy group is converted to a superior leaving group. The cyclization of haloamines is called the Gabriel Ethylenimine Method, while the cyclization of amino alcohols is called the Wenker synthesis.
Aziridine can be synthesized by the addition of nitrenes produced by photolysis or thermal decomposition of azides to alkenes. Aziridine is also formed when a triazoline obtained by cycloaddition of an azide with an alkene is pyrolyzed or photolyzed to liberate a nitrogen atom.
Furthermore, ring-opening of epoxides in the presence of sodium azide and removal of the nitrogen atom by reduction with triphenylphosphine also yields aziridine.
2. Reaction of Aziridine
Aziridine rings, which are highly sterically strained, undergo ring-opening reactions with nucleophiles. When amines, alcohols, and thiols are added to aziridines, aminoethylation products can be formed. Gilman reagent and alkyl lithium are also effective nucleophiles.
Ring-opening reactions have also been applied to the asymmetric synthesis of oseltamivir using trimethylsilyl azides and asymmetric ligands.
Aziridines produce a wide variety of polymer derivatives called polyethyleneimines (PEIs). Polyethyleneimine is useful as a cross-linker and a precursor for coatings.