Grignard Reaction

(redirected from Grignard reagents)
Also found in: Medical.

Grignard reaction

[grin′yär rē‚ak·shən]
(organic chemistry)
A reaction between an alkyl or aryl halide and magnesium metal in a suitable solvent, usually absolute ether, to form an organometallic halide.

Grignard Reaction


a general method of synthesizing organic substances using mixed organomagnesium compounds (Grignard reagents) of the type RMgX, where R is an aliphatic or aromatic radical and X is a halogen (usually Br or I, more rarely C1). The Grignard reaction was discovered by the French chemist F. A. V. Grignard in 1900. Grignard reagents are obtained by the action of Mg on alkyl or aryl halides in an ether medium and are usually used in the form of ether solutions. Methods of preparing RMgX using solvents other than ether have been worked out for industrial use. An atom of carbon bound to an atom of magnesium carries a partial negative charge δ-, so that compounds of RMgX are reactive in relation to reagents with positively charged reaction centers:

When RMgX reacts with C02, carboxylic acids are formed. With formaldehyde (CH2=0) primary alcohols are formed; with aldehydes (RCH=0), secondary alcohols; and with ketones (RR’C=0), tertiary alcohols. The use of the Grignard reaction to obtain ketones from carboxylic acids and their derivatives, for example,


is limited. It is difficult to stop the reaction at the ketone-forming stage, and ordinarily tertiary alcohols are formed in considerable quantity.

Grignard reagents react easily with halides of elements, for example.

2RMgX + HgCl2 → R2Hg + 2MgXCl

In this manner it is possible to obtain organic compounds of Be, Cd, B, Si, Ge, Pb, P, and other elements. Grignard reagents react with oxygen and sulfur to form alcohols and thioalcohols, respectively. When reacting with water, alcohols, acids, amines, and other compounds containing a labile atom of hydrogen, the RMgX decompose and hydrocarbons are formed:

RMgX + R’OH → R—H + R’OMgX

If CH3MgI is used, then it is possible to determine the amount of active hydrogen by the amount of methane released (the Chugaev-Tserevitinov method).


Ioffe, S. T., and A. N. Nesmeianov. Metody elementoorganicheskoi khimii. Moscow, 1963.
References in periodicals archive ?
The substitution of fluorine with an ethynyl anion can be accomplished by using a lithium organometallic reagent, Scheme 2, or a Grignard reagent, Scheme 3.
2006; Goze & Ziessel 2007), ethynyl nucleophiles reveal that only the disubstituted product can be produced when using a lithium reagent (Scheme 2), while either the monosubstituted or disubstituted product can be produced when using a Grignard reagent (Scheme 3).
Thus, the formation of the monosubstituted product prevails when using a Grignard reagent at 0[degrees]C.
In the case of the Grignard reagent, the monosubstituted product is achievable at 0 [degrees]C because the activation energy for the second substitution is higher than that of the first.
The monosolvated Grignard reagent in toluene is particularly liable to complexation with a silane.
For a monosolvated Grignard reagent in toluene under pseudo-first-order conditions, the concentration of the free ether is negligible and the reaction can be rewritten as
After the reaction mixture had cooled down the concentration of the Grignard reagent was determined.
The reaction vessel equipped with a magnetic stirrer and containing 40 mL of the Grignard reagent was thermostatted.
05 mL of silane was added to 15 mL of the Grignard reagent (providing a 20-40-fold excess of the Grignard reagent), and the temperature change of the reaction solution (less than 1[degrees]C) was recorded as a plot of temperature vs.
The first three entries in Table 2 represent a variation of the donor solvent in the Grignard reagent.
Replacement of the n-butyl group by isopropyl in the Grignard reagent increases the equilibrium constant by a factor of two in accordance of increasing hindrance to coordination with the donor.