Ethyl iodide

 ( Iodoalkanes ) 

Ethyl iodide (also iodoethane) is a colorless flammable chemical compound. It has the chemical formula C₂H₅I and is prepared by heating ethanol with iodine and phosphorus. Merck Index of Chemicals and Drugs, 9th ed., monograph 3753 On contact with air, especially on the effect of light, it decomposes and turns yellow or reddish from dissolved iodine.

It may also be prepared by the reaction between hydroiodic acid and ethanol, typically by generating the hydroiodic acid in situ via an iodide salt (such as sodium iodide) and an acid (such as sulfuric acid), after which the ethyl iodide is distilled off. Ethyl iodide should be stored in the presence of copper powder to avoid rapid decomposition, though even with this method samples do not last more than 1 year.

Because iodide is a good leaving group, ethyl iodide is an excellent ethylating agent. It is also used as the hydrogen radical promoter.

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Production Ethyl iodide is prepared by using red phosphorus, absolute ethanol and iodine. The iodine dissolves in the ethanol, where it reacts with the solid phosphorus to form phosphorus triiodide.

Csámpai, A (2025). 9789633121290, Eötvös kiadó. ISBN 9789633121290

During this process, the temperature is controlled.

3 C₂H₅OH + PI₃ → 3 C₂H₅I + H₃PO₃

The crude product is purified by distillation.

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