Aziridine

Aziridine is an organic compound consisting of the three-membered heterocycle (CH₂)₂NH.[5][6] It is a colorless, toxic, volatile liquid that is of significant practical interest.[7] Its derivatives, also referred to as aziridines, are of broader interest in medicinal chemistry.

Aziridine

Names
Preferred IUPAC name Aziridine
Systematic IUPAC name Azacyclopropane
Other names Azirane Ethylene imine Aminoethylene Dimethyleneimine Dimethylenimine Ethylimine
Identifiers
CAS Number	151-56-4^Y
3D model (JSmol)	Interactive image
Beilstein Reference	102380
ChEBI	CHEBI:30969^Y
ChEMBL	ChEMBL540990^Y
ChemSpider	8682^Y
ECHA InfoCard	100.005.268
EC Number	205-793-9
Gmelin Reference	616
KEGG	C11687^Y
PubChem CID	9033
RTECS number	KX5075000
UNII	54P5FEX9FH
UN number	1185
CompTox Dashboard (EPA)	DTXSID8020599
InChI InChI=1S/C2H5N/c1-2-3-1/h3H,1-2H2^Y Key: NOWKCMXCCJGMRR-UHFFFAOYSA-N^Y InChI=1/C2H5N/c1-2-3-1/h3H,1-2H2 Key: NOWKCMXCCJGMRR-UHFFFAOYAE
SMILES C1CN1
Properties
Chemical formula	C2H5N
Molar mass	43.069 g·mol^−1
Appearance	Colorless oily liquid[1]
Odor	ammonia-like[2]
Density	0.8321 g/mL 20 °C[3]
Melting point	−77.9 °C (−108.2 °F; 195.2 K)
Boiling point	56 °C (133 °F; 329 K)
Solubility in water	miscible
Vapor pressure	160 mmHg (20° C)[2]
Hazards
Main hazards	highly flammable and toxic
GHS pictograms
GHS Signal word	Danger
GHS hazard statements	H225, H300, H310, H314, H318, H330, H340, H350, H411
GHS precautionary statements	P201, P202, P210, P233, P240, P241, P242, P243, P260, P262, P264, P270, P271, P273, P280, P281, P284, P301+310, P301+330+331, P302+350, P303+361+353, P304+340, P305+351+338, P308+313, P310
NFPA 704 (fire diamond)	3 4 3
Flash point	−11 °C (12 °F; 262 K)
Autoignition temperature	322 °C (612 °F; 595 K)
Explosive limits	3.6–46%
Lethal dose or concentration (LD, LC):
LC50 (median concentration)	250 ppm (rat, 1 hr) 250 ppm (guinea pig, 1 hr) 62 ppm (rat, 4 hr) 223 ppm (mouse, 2 hr) 56 ppm (rat, 2 hr) 2236 ppm (mouse, 10 min)[4]
LCLo (lowest published)	25 ppm (guinea pig, 8 hr) 56 ppm (rabbit, 2 hr)[4]
NIOSH (US health exposure limits):
PEL (Permissible)	OSHA-Regulated Carcinogen[2]
REL (Recommended)	Ca[2]
IDLH (Immediate danger)	Ca [100 ppm][2]
Related compounds
Related heterocycles	Borirane Ethylene oxide Thiirane
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

For the general class, see Aziridines.

Structure

The bond angles in aziridine are approximately 60°, considerably less than the normal hydrocarbon bond angle of 109.5°, which results in angle strain as in the comparable cyclopropane and ethylene oxide molecules. A banana bond model explains bonding in such compounds. Aziridine is less basic than acyclic aliphatic amines, with a pKa of 7.9 for the conjugate acid, due to increased s character of the nitrogen free electron pair. Angle strain in aziridine also increases the barrier to nitrogen inversion. This barrier height permits the isolation of separate invertomers, for example the cis and trans invertomers of N-chloro-2-methylaziridine.

Synthesis and uses

Linear PEI fragment, derived from aziridine.

Typical branched PEI fragment, derived from aziridine.

Aziridine is produced industrially from aminoethanol via two related routes. The Nippon Shokubai process requires an oxide catalyst and high temperatures to effect the dehydration. In the Wenker synthesis, 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.[7]

Aziridine forms a wide variety of polymeric derivatives, known as polyethylenimines. These and related species are useful crosslinking agents and precursors for coatings.[7]

Safety

Aziridine is highly toxic with an LD₅₀ of 14 mg (oral, rats). It is a skin irritant. As an alkylating agent, it also a mutagen.[7] It is subject to attack and ring-opening by endogenous nucleophiles such as nitrogenous bases in DNA base pairs, resulting in potential mutagenicity.[8][9][10]

See also

• Binary ethylenimine, a dimeric form of aziridine

References

1. "Aziridine" (PDF). Re-evaluation of Some Organic Chemicals, Hydrazine and Hydrogen Peroxide. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. 71. 1999.
2. NIOSH Pocket Guide to Chemical Hazards. "#0274". National Institute for Occupational Safety and Health (NIOSH).
3. Weast, Robert C.; et al. (1978). CRC Handbook of Chemistry and Physics (59th ed.). West Palm Beach, FL: CRC Press. ISBN 0-8493-0549-7.
4. "Ethyleneimine". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
5. Gilchrist, T.L. Heterocyclic chemistry. ISBN 978-0-582-01421-3.
6. Epoxides and aziridines – A mini review Albert Padwa, S. Shaun Murphree Arkivoc (JC-1522R) pp. 6–33 Online article
7. Steuerle, Ulrich; Feuerhake, Robert (2006). "Aziridines". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a03_239.pub2.
8. Kanerva L, Keskinen H, Autio P, Estlander T, Tuppurainen M, Jolanki R (May 1995). "Occupational respiratory and skin sensitization caused by polyfunctional aziridine hardener". Clin Exp Allergy. 25 (5): 432–9. doi:10.1111/j.1365-2222.1995.tb01074.x. PMID 7553246.
9. Sartorelli P, Pistolesi P, Cioni F, Napoli R, Sisinni AG, Bellussi L, Passali GC, Cherubini Di Simplicio E, Flori L (2003). "Skin and respiratory allergic disease caused by polyfunctional aziridine". Med Lav. 94 (3): 285–95. PMID 12918320.
10. Mapp CE (2001). "Agents, old and new, causing occupational asthma". Occup. Environ. Med. 58 (5): 354–60. doi:10.1136/oem.58.5.354. PMC 1740131. PMID 11303086.