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Additional recommended knowledge
The preparation of EtBr stands as a model for the synthesis of alkyl bromides in general. It is usually prepared by the addition of HBr to ethylene:
Ethyl bromide is inexpensive and would rarely be prepared in the laboratory. Convenient laboratory syntheses include the action of phosphorus tribromide or thionyl bromide on ethanol. EtBr forms when ethanol is treated with HBr or hydrobromic acid, although this reaction also affords diethyl ether.
In organic synthesis, EtBr is the synthetic equivalent of the ethyl carbocation (Et+) synthon. In reality, such a cation is not actually formed. For example, carboxylates salts are converted to ethyl esters, carbanions to ethylated derivatives, thiourea into ethylisothiouronium salts, and amines into ethylamines.
Being a liquid at room temperature but still very volatile, EtBr is an inexpensive reagent for the preparation of Grignard reagents, which traditionally were used as strong base. Thus EtMgBr deprotonates alkynes:
This application has been supplanted by the wide availability of organolithium reagents.
Halocarbons in general are potentially dangerous alkylating agents. Bromides are more superior alkylating agents than chlorides, thus exposure to EtBr should be minimized. EtBr is classified by the State of California as carcinogenic and a reproductive toxin.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Bromoethane". A list of authors is available in Wikipedia.|