Question

A Grignard reaction was performed using the following steps:

Step 1: Addition of Grignard Reagent: Phenyl Magnesium Bromide

a solution of phenyl magnesium bromide (2.7 mL of a 3.0 M solution in anhydrous diethyl ether) and 5 mL of anhydrous diethyl ether was dispensed into the round-bottom flask and stirred with a stir bar.

Step 2: Addition Formation: Reaction with Benzophenone

A solution of 0.72 g (mp = 48-49 degrees C) of benzophenone and 2.0 mL of anhydrous diethyl ether was prepared and added in 1.0 mL portions to the reaction flask. It was then left to sit for 13 minutes with occasional stirring.

Step 3: Acidification and Hydrolysis

6.0 mL of 3 M hydrochloric acid was added to the reaction flask to neutralize the reaction mixture.

Step 4: Isolation

Two distinct clear layers formed and using a separatory funnel the lower aqueous layer was removed and discarded. An equal volume of saturated sodium chloride solution was added to the separatory funnel and the lower aqueous layer was removed and discarded again. The remaining organic layer was transferred to a centrifuge tube and a small amount of anhydrous sodium sulfate was added and left to sit for 5 minutes. The ether solution was decanted into a flask and a small amount of methyl tert-butyl ether was added to the sodium sulfate to remove any remaining product. The additional ether was decanted into the flask as well.

Explain the treatment of the reaction mixture with 3 M HCl after the addition of benzophenone. (Step 3)

Use a mechanism to complete your answer.

Answer 1