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Grignard reagents or Grignard compounds are chemical compounds with the general formula R−Mg−X, where X is a halogen and R is an organic group, normally an alkyl or aryl. Two typical examples are methylmagnesium chloride Cl−Mg−CH 3 and phenylmagnesium bromide (C 6 H 5)−Mg−Br. They are a subclass of the organomagnesium compounds.
A solution of a carbonyl compound is added to a Grignard reagent. (See gallery) An example of a Grignard reaction (R 2 or R 3 could be hydrogen). The Grignard reaction (French:) is an organometallic chemical reaction in which, according to the classical definition, carbon alkyl, allyl, vinyl, or aryl magnesium halides (Grignard reagent) are added to the carbonyl groups of either an aldehyde or ...
The Hauser bases are prepared by treating a secondary amine with a Grignard reagent: R 2 NH + R′MgX → R 2 NMgX + R′H X = Cl, Br, I (:R 2 NH = diisopropylamine, TMP) Like many organolithium reagents, Hauser bases are generally used for metalation reagents. iPr 2 NMgBr selectively magnesiate carboxamides.
The Schlenk equilibrium, named after its discoverer Wilhelm Schlenk, is a chemical equilibrium taking place in solutions of Grignard reagents [1] [2] and Hauser bases [3] [4]. 2 RMgX ⇌ MgX 2 + MgR 2
Turbo-Hauser bases are used as metalation/deprotonation reagents. In this way, they resemble some organolithium reagents. The lithiated compounds, however, are only stable at low temperatures (e.g. -78 °C) and suffer competing addition reactions (like e.g. Chichibabin reactions). In contrast, the magnesium compounds are less reactive.
The reaction mixture containing the Grignard reagent is allowed to warm to room temperature in a water bath to allow excess dry ice to evaporate. Any remaining Grignard reagent is quenched by the addition of water. Dilute hydrochloric acid is added to the reaction mixture to protonate the benzoate salts, as well as to dissolve the magnesium ...
Reactions [ edit ] 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 : [ 1 ]
Grignard reagents of acetylene or alkynes can be used to perform alkynylations on compounds that are liable to polymerization reactions via enolate intermediates. However, substituting lithium for sodium or potassium acetylides accomplishes similar results, often giving this route little advantage over the conventional reaction. [1]