Ethylmagnesium bromide is a Grignard reagent with formula C2H5MgBr or C2H5Mg+·Br−, namely a magnesium ion with a covalent bond to an ethyl group and an ionic bond to a bromine anion. It is widely used in the laboratory synthesis of organic compounds.
Ethylmagnesium bromide Wikipedia
Apart from acting as the synthetic equivalent of an ethyl anion synthon for nucleophilic addition, ethylmagnesium bromide may be used as a strong base to deprotonate various substrates such as alkynes:
RC≡CH + EtMgBr → RC≡CMgBr + EtH
In this application, ethylmagnesium bromide has been supplanted by the wide availability of organolithium reagents.
Ethylmagnesium bromide is commercially available, usually as a solution in diethyl ether or tetrahydrofuran. It may be prepared in the normal manner of Grignard reagents — by reacting bromoethane with magnesium in diethyl ether:
EtBr + Mg → EtMgBr