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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 first step of the Bouveault aldehyde synthesis is the formation of the Grignard reagent. Upon addition of a N , N -disubstituted formamide (such as dimethylformamide ) a hemiaminal is formed, which can easily be hydrolyzed into the desired aldehyde.
Like all Grignard reagents, propylmagnesium bromide is a strong electrophile, sensitive to both water and air. The propylmagnesium halides are the simplest Grignard reagents to exhibit isomerism. Isopropylmagnesium chloride is the primary synthetic equivalent of the isopropyl group. [1]
Examples of Grignard reagents are phenylmagnesium bromide and ethylmagnesium bromide. These simplified formulas are deceptive: Grignard reagents generally exist as dietherates, RMgX(ether)2. As such they obey the octet rule. Grignard reagents participate in the Schlenk equilibrium. Exploiting this reaction is a way to generate dimethylmagnesium.
The Bodroux–Chichibabin aldehyde synthesis is a chemical reaction whereby a Grignard reagent is converted to an aldehyde one carbon longer. Reaction of a Grignard reagent with triethyl orthoformate gives an acetal, which can be hydrolyzed to an aldehyde. For example, the synthesis of n-hexanal: [1] Bodroux-Chichibabin hexanal [1]
As with most Grignard reagents, methylmagnesium chloride is highly solvated by ether solvents via coordination from two oxygen atoms to give a tetrahedrally bonded magnesium center. Like methyllithium, it is the synthetic equivalent to the methyl carbanion synthon. It reacts with water and other protic reagents to give methane, e.g.,:
The traditional method for generating the aryl Grignard reagent proceeds less predictably: slow, heterogeneous: XC 6 H 4 Br + Mg → XC 6 H 4 MgBr. Furthermore, traditional routes to Grignard reagents has limited functional group compatibility, whereas the Turbo-Grignard method tolerates other halides, some ester groups, and nitriles.