Halides reaction with magnesium metal

In a Grignard reaction, an alkyl halide reacts with magnesium metal in an anhydrous ether solvent to create an organometallic reagent. 

Grignard reagents are prepared from organic halides by reaction with magnesium a Group II metal... 

The reaction of magnesium metal with an alkyl or aryl halide in diethyl ether is the standard method for synthesis of Grignard reagents. The order of reactivity of the halides is RI > RBr > RC1. 

The preparation of a Grigncird reagent begins with magnesium metal and dry ether (in most cases, either diethyl ether or THF, tetrahydrofuran). The ether cleans the surface of the metal and takes the reagent into solution for reaction. (If either the ether or the reaction vessel contains moisture, the yield is poor.) The magnesium then reacts with either an alkyl halide or an aryl halide. The ease of reactivity decreases in the order R1 > RBr > RCl. Iodides may react too rapidly, but chlorides may react too slowly. Thus bromides are usually the best. The general reaction is... 

Grignard reagents—phenylmagnesium bromide in this case—are always prepared by reaction of magnesium metal and the corresponding halide. Starting with bromobenzene, a suitable synthesis is described by the sequence... 

Firstly, the reaction with alkali metals, magnesium or other similarly reactive metals, mostly in ethereal solution. The tendency toward formation of the metal halide is the probable driving force of the reaction. Secondly, the reaction with silicon metal at about 1000 °C. This type is called a transport reaction because silicon metal is transported in the gaseous phase ... 

In 1901, Victor Grignard, prepared an organomagnesium halide by the reaction of an organic halide with magnesium metal in dry ether. 

When a Grignard reagent is formed by reaction of an alkyl halide with magnesium metal, the stereochemical configuration at the Q -carbon is randomized. Radical intermediates in the formation of the Grignard reagent (see Section 4.2) are held responsible. Very rarely, as in the formation of (17), is there incomplete racemization ... 

In 1912 Victor Grignard received the Nobel prize in chemistry for his work on the reaction that bears his name, a carbon-carbon bond-forming reaction by which almost any alcohol may be formed from appropriate alkyl halides and carbonyl compounds. The Grignard reagent is easily formed by reaction of an alkyl halide, in particular a bromide, with magnesium metal in anhydrous ether. Although the reaction can be written and thought of as simply... 

Subsequently, kinetic studies reported by Whitesides and collaborators [81] provided further support for the view that the rate-determining step in formation of alkyl Grignard reagents involves electron transfer from the metal surface. The kinetics of the reaction of an organic halide RjX with magnesium were described by Eq. (3), in which S g accounted for the characteristics of magnesium surface that influence the rate, and an analogous... 

Organophosphorus compounds find wide use in the chemical industry as catalysts, intermediates, complexes, and end-use products. Arylphosphines and phosphine oxides are often produced by the reaction of a preformed Grignard reagent with a halophosphine or phosphine oxide. Yields are reduced by the production of unwanted side-reaction products such as biaryls. These unwanted products are reduced when the reaction is conducted under Barbier conditions. When alkyl and aryl halides are reacted with magnesium metal, a trihalophosphine or phosphine oxide, a metal halide or amine catalyst, in THE benzene mixtures, at reflux, good yields of phosphines or phosphine oxides are obtained [74]. For example, triphenylphosphine can be prepared in a 97.2% yield from the reaction of bromobenzene, trichlorophosphine, magnesium metal, aluminum chloride, and sodium chloride in THF-benzene at 70 80 C. 

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