Grignard Reaction

Source: Vy M. Dong and Faben Cruz, Department of Chemistry, University of California, Irvine, CA

This experiment will demonstrate how to properly carry out a Grignard reaction. The formation of an organometallic reagent will be demonstrated by synthesizing a Grignard reagent with magnesium and an alkyl halide. To demonstrate a common use of a Grignard reagent, a nucleophilic attack onto a carbonyl will be performed to generate a secondary alcohol by forming a new C-C bond.

1. Grignard Reagent Formation

Flame-dry a round bottom flask equipped with a magnetic stir bar.
Add magnesium (Mg, 1.1 equiv.) to the round bottom flask.
Add a small amount of iodine (I₂, a few crystals). Addition of iodine is to help remove any MgO on the surface of the Mg. Removing MgO allows for Mg and the aryl/alkyl halide to come in contact and react. Sonication or addition of methyl iodide or 1,2-dib

The purified product should have the following ¹H NMR spectrum: ¹H NMR δ 7.23-7.39 (m, 5H), 6.60 (d, J = 16.0 Hz, 1H), 6.23 (dd, J = 6.4 Hz, 1H), 5.84 (m, 1H), 5.14-5.20 (m, 2H), 4.35 (q, J = 6.4 Hz, 1H), 2.37-2.43 (m, 2H), 1.9 (br s, 1H).

This experiment has demonstrated how to synthesize a Grignard reagent from an aryl/alkyl halide and how to use the Grignard reagent to perform a nucleophilic addition onto a carbonyl compound to construct a new carbon-carbon bond.

The Grignard reaction is widely applied in the synthetic chemistry world, and is used in university research labs, national laboratories, and pharmaceutical companies. Simple Grignard reagents are commercially available, but often times unique and specialized Grignar