Lab Report Grignard Reagent

Introduction

The purpose of this week’s lab was to enhance our understanding of the Grignard reagents that were examined in lecture. In this lab, a Grignard reagent will be prepared through the reaction of magnesium turnings and bromobenzene. Instead of isolating the product it will then be combined with benzophenone, which will give the final product of triphenylmethanol.

Procedure

To start this experiment the first step is to equip a 500-mL three-neck round bottom flask with a reflux condenser, dropping funnel, glass stopper, and a calcium chloride drying tube. Place a heating mantle under the flask in order to aid stirring. Next, grind 0.0411 moles of magnesium turnings and place them into the flask. Once added, prepare a 1.1 equivalent of bromobenzene, and then

The experimental melting point was calculated to be 159.0-159.6°C, which is very accurate compared to the actual melting range of 160-163°C. The percent yield came out to be 26.89%, which is low but is consistent with other in the class due to the difficult nature of forming the trimethylmethanol crystals. Overall, this was a successful experiment because in the end there was a decent amount of pure crystal product.

Questions

1. The triphenymethanol product was a very fine white powder that had a slight yellow tint to it. The experimental melting point was calculated to be 159.0-159.6°C, which is very accurate compared to the actual melting range of 160-163°C. The percent yield came out to be 26.89%, which is most likely low due to using heating plates to heat the end reaction instead of the recommended steam baths.
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5. The added hexane is denser than the aqueous solution, which causes the reaction to run faster and reduces the amount of lost product because it creates a density difference between the product and solvent.
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