The Preparation Of Grignard Reagents

1417 Words Oct 22nd, 2016 6 Pages
The preparation of Grignard reagents typically involves the reaction of an alkyl halide or aryl halide with magnesium metal in an anhydrous ethereal solvent. This reaction results in the formation of a carbon-magnesium complex within an alkyl magnesium halide or aryl magnesium halide. Grignard reagents are considered to be strong nucleophiles and strong bases that have the ability to react with acidic proton sources and carbonyl functional groups. The preparation of Grignard reagents must be conducted in aprotic solvents to minimize interactions with strong proton sources that may result in undesired products. Furthermore, the solvent chosen for the reaction must dissolve everything in solution. Commonly used solvents in Grignard reactions are diethyl ether and tetrahydrofuran (THF). They are preferred over hexane solvents due to the presence of an oxygen atom which contains a lone electron pair that attracts the partially positive magnesium metal, resulting in increased stability. As mentioned previously, Grignard reagents are strong nucleophiles. Thus, there is a possibility that they may react with other molecules in side-reactions. One such side-reaction involves the Grignard reagent reacting with molecular oxygen (O2) to form a peroxide molecule. In another side-reaction, the Grignard reagent may react with carbon dioxide (CO2) to form a carboxylate molecule. These side-reactions can pose a problem since molecular oxygen and carbon dioxide are in excess under normal…
Open Document