Magnesium Turnings For Grignard

Grignard reagents are used as intermediates in the production of complex molecules, since they can be used to form new carbon–carbon bonds, e.g. in the formation of active pharmaceutical ingredients. Side product formation like Wurtz coupling diminishes the selectivity in Grignard reagent formation and therefore side product formation needs to be reduced. It was found that the different pumping behaviours of a syringe pump, a valveless rotary piston pump and a micro annular gear pump and the obtained residence time distributions have an impact on the selectivity of the Grignard reagent formation. Selectivity can also be enhanced by the available magnesium surface and by choosing a tubular flow reactor instead of a batch reactor, showing the importance of choosing the right equipment and parameters for the specific reaction system.

Organomagnesium halides, better known as Grignard reagents, are formed by the exothermic reaction of metallic magnesium (usually turnings or powder) with a halide in an anhydrous, etheric solvent. Grignard reagents can be used for the formation of new carbon–carbon bonds and are one of the most important intermediates in such reactions. Both on a small scale in a glass flask in chemical laboratories and on a larger scale in stirred vessels in the chemical industry, Grignard reagents are prepared in a dosing-controlled semi-batch process based on placing a certain mass of magnesium together with a small amount of the halide in the solvent in the stirred vessel and then slowly adding the remaining halide–solvent mixture.