Triphenylmethanol Synthesis: Grignard Reaction

Set up a dry round-bottom flask on a hot plate with a stir bar, then add 1.5 grams of fresh magnesium turnings and 8 milliliters of anhydrous diethyl ether. Add a tiny speck of iodine crystal to help remove the oxide layer from the magnesium.

Connect a three-way Claisen adapter with a Liebig condenser and pressure-equalizing addition funnel to the flask. Add a mixture of 6 milliliters of dry bromobenzene in 25 milliliters of anhydrous ether to the addition funnel, then slowly drip it into the flask with stirring.

Monitor the exothermic reaction as the iodine color disappears and turbidity appears, indicating formation of phenyl magnesium bromide. After all bromobenzene is added, reflux the mixture for 15 minutes to ensure completion, then allow it to cool.

Dissolve 12 grams of benzophenone in 25 milliliters of anhydrous ether and slowly add it to the Grignard reagent. Observe the solution turn bright pink and eventually form a crystalline precipitate as the product becomes supersaturated in the ether solvent.

Prepare 30 milliliters of 10% sulfuric acid solution by diluting concentrated sulfuric acid in distilled water over ice. Transfer the flask contents to the ice-cold acidified solution with stirring to protonate the triphenyl methoxy anion and form triphenylmethanol.

Pour the mixture into a separatory funnel and separate the ether layer from the aqueous layer containing magnesium sal. Combine the ether extracts and perform a simple distillation to remove the ether, which is saved for future use.

Add distilled water to the reaction flask and perform steam distillation to remove unreacted materials and by-products. Filter the crude yellow product and recrystallize it from hot 96% ethanol to obtain white crystalline triphenylmethanol.

Vacuum filter the recrystallized product and dry it completely. Weigh the dried product (10.1 grams obtained, 64% yield) and confirm its identity by measuring the melting point (160-163°C) using a Thiele tube.