Grignard Reaction Lab Report

Discussion The purpose of this lab was to properly prepare a Grignard reagent from an unknown aryl halide and then to use the prepared Grignard reagent with solid carbon dioxide and an acid quench to form a carboxylic acid.

Organometallics are compounds that have a carbon bonded to a metal; C-M, where M is any transition metal. In an organometallic, the carbon has a partial negative charge and is considered electron-rich due to the bond with the positively charged metal. Because of this partial negative charge, the carbon acts as a nucleophile and is able to be used in reactions to produce new bonds between carbon atoms by attaching to another carbon that acts as an electrophile.

Grignard reagents specifically are organometallics that have

In order to control this rate, the halide should be added slowly, dropwise and the reaction should be placed in an ice water bath following completion. Some side reactions that could occur when preparing a Grignard are the Grignard with water which destroys the Grignard reagent and forms a hydrocarbon and magnesium salt. This is why keeping and using equipment that was dry was so important as well as using an aprotic solvent and reacting in air that is not humid/full of moisture. Two side reactions that are problematic but are not usually a concern are the Grignard with either O2 or CO2. These are negligible side reactions because the O2/CO2 present in the diethyl ether solvent is very small. Another problematic side reaction that cannot be avoided but can be minimized is the coupling reaction of the Grignard with the halide which forms a symmetrical hydrocarbon. This coupling reaction is minimized by keeping the concentration of the halide low and using dilute solutions done by keeping the reaction stirring and adding in halide slowly. At the end of this reaction, there comes a point where the original halide is more likely to react with the Grignard reagent than it is with the

This number was found by dividing the 0.282 g by the number of moles of NaOH, 0.00201 moles (which was found by dividing the 20.1 mL used by 1000 and multiplying that number by the 0.1 M concentration). The molecular weight data can be used to compare and identify experimental data to that of known data in order to identify the unknown. The known molecular weight of benzoic acid is 122.12 g/mol, so there were errors in obtaining the molecular weight from the lab as the lab molecular weight is almost 20 g/mol higher. These errors could have been caused by impurities remaining in the final product such as the previously used/present magnesium, iodine, or the original