Grignard Reaction

Assemble a closed system with a round bottom flask, Claisen adapter, rubber septum, and drying tube packed with calcium chloride. Dry the round bottom flask in an oven and place it on a stir plate to prepare for the anhydrous reaction.

Cut magnesium strips to 0.15 grams total and place in the dried flask with a stir bar. Prepare a separate vial with 0.7 mL bromobenzene and 4 mL anhydrous diethyl ether.

Gradually add the bromobenzene-ether mixture to the magnesium metal using a syringe through the septum over 15 minutes. If needed, add iodine crystals to initiate bubbling, gently heat as necessary, and continue adding the bromobenzene solution until magnesium is consumed after approximately 30 minutes total.

Dissolve 1.09 grams of benzophenone in 2 mL anhydrous diethyl ether and add it to the Grignard reagent via syringe. Monitor the reaction for 15 minutes as the brownish mixture forms the intermediate product.

Slowly add hydrochloric acid to the reaction mixture using a glass pipette, then add the remainder with a graduated cylinder. This converts the magnesium alkoxide intermediate into triphenylmethanol and reacts any unreacted magnesium, producing hydrogen gas evolution.

Add approximately 8 mL diethyl ether and perform a liquid-liquid extraction using a separatory funnel, collecting both the ether and aqueous layers separately. Wash the aqueous layer once more with 5 mL ether, combine both ether layers, and dry with sodium sulfate.

Evaporate the ether solvent on a hot plate to obtain an oily solid mixture. Add 3 mL petroleum ether and heat gently to dissolve the biphenyl impurity while the desired triphenylmethanol remains insoluble, then collect crystals via vacuum filtration.

Weigh and transfer the dried crystals to a sample vial for analysis. Run a background scan on the IR spectrometer, load the sample, perform a sample scan, and print the resulting IR spectrum for structural analysis.