Facile Grignard Reaction Demonstration Using Molecular Sieved Dried Solvent

Abstract

Methods involving C–C bond formation are continuously being innovated due to their importance in the creation and modification of important organic molecules. The classic Grignard reaction demonstrates C–C bond formation with reagents that are usually accessible in undergraduate laboratory classes. Oftentimes, to make the Grignard reaction viable, the reactions are assisted by heating at elevated temperatures or with the use of a catalyst accompanied by solvents that have been dried using highly reactive sodium metal (Na0)conditions which increase the risk of a laboratory fire or explosion. For this work, a method to conduct Grignard reactions under mild conditions utilizing sand-paper-polished Mg ribbons and solvent dried using molecular sieves was developed. The conscientious, accessible, and easy-to-follow preparation of both the solvent and the Mg ribbons is found to contribute more to the percent conversion of reagents to products. The average percent conversion with the proposed method ranged from 76.8% to 99.5% based on 1H NMR results. This makes the Grignard demonstration possible even for the most humid, tropical locations.

Crush It Safely: Safety Aspects of Mechanochemical Grignard Synthesis

“…4 Alternatively, the metal surface can also be mechanically activated by ultrasonication, 5,6 dry stirring, 7 or sandpapering. 8 Nevertheless, the successful initiation cannot be guaranteed in every case, and there are chances that the reaction might be subject to a long delay or might not occur at all. Mechanochemical-assisted syntheses, whereby the reactions take place by grinding together the reactants, often without requiring any solvents or a protective inert atmosphere, have received recent widespread attention as a green and convenient alternative to conventional synthesis.…”

“…Numerous attempts have been made to facilitate the Grignard reagent formation, which involves some kind of metal surface activation including the addition of an etching agent such as iodine, 1,2-dibromoethane, or diisobutylaluminum hydride (DIBAL-H) or by using a freshly prepared highly dispersed magnesium powder . Alternatively, the metal surface can also be mechanically activated by ultrasonication, , dry stirring, or sandpapering . Nevertheless, the successful initiation cannot be guaranteed in every case, and there are chances that the reaction might be subject to a long delay or might not occur at all.…”