Cyclopropane
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Preferred IUPAC name
Cyclopropane
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3D model (Jmol)
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| ChemSpider | |||
| ECHA InfoCard | 100.000.771 | ||
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PubChem CID
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| Properties | |||
| C3H6 | |||
| Molar mass | 42.08 g/mol | ||
| Appearance | Colorless gas | ||
| Odor | Sweet smelling | ||
| Density | 1.879 g/L (1 atm, 0 °C) | ||
| Melting point | −128 °C (−198 °F; 145 K) | ||
| Boiling point | −33 °C (−27 °F; 240 K) | ||
| Acidity (pKa) | ~46 | ||
| -39.9·10−6 cm3/mol | |||
| Hazards | |||
| Main hazards | Highly flammable Asphyxiant |
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| Safety data sheet | External MSDS | ||
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Cyclopropane is a cycloalkane molecule with the molecular formula C3H6, consisting of three carbon atoms linked to each other to form a ring, with each carbon atom bearing two hydrogen atoms resulting in D3hmolecular symmetry. Cyclopropane and propene have the same molecular formula but have different structures, making them structural isomers.
Cyclopropane is an anaesthetic when inhaled. In modern anaesthetic practice, it has been superseded by other agents, due to its extreme reactivity under normal conditions: when the gas is mixed with oxygen, there is a significant risk of explosion.
Cyclopropane was discovered in 1881 by August Freund, who also proposed the correct structure for the new substance in his first paper. Freund treated 1,3-dibromopropane with sodium, causing an intramolecular Wurtz reaction leading directly to cyclopropane. The yield of the reaction was improved by Gustavson in 1887 with the use of zinc instead of sodium. Cyclopropane had no commercial application until Henderson and Lucas discovered its anaesthetic properties in 1929; industrial production had begun by 1936.
Cyclopropane was introduced into clinical use by the American anaesthetist Ralph Waters who used a closed system with carbon dioxide absorption to conserve this then-costly agent. Cyclopropane is a relatively potent, non-irritating and sweet smelling agent with a minimum alveolar concentration of 17.5% and a blood/gas partition coefficient of 0.55. This meant induction of anaesthesia by inhalation of cyclopropane and oxygen was rapid and not unpleasant. However at the conclusion of prolonged anaesthesia patients could suffer a sudden decrease in blood pressure, potentially leading to cardiac dysrhythmia; a reaction known as "cyclopropane shock". For this reason, as well as its high cost and its explosive nature, it was latterly used only for the induction of anaesthesia, and has not been available for clinical use since the mid 1980s. Cylinders and flow meters were coloured orange.
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