CHEM 3720L

Preparation and Reaction of Phenylmagnesium Bromide

O

Br MgBr + Mg H , H2O C C ether O MgBr OH

Separatory Funnel 1. Assemble the apparatus shown at left. Dry with a Calcium Chloride heat gun (CAUTION:HOT, see lab instructor for Drying Tube instructions on proper use and safety). 2. Place 0.5 g (20.6 mmol) Mg metal in the 100 mL round bottom flask. Thermometer Adapter 3. Add one or two Iodine crystals with the Mg. 4. Allow the apparatus to cool to room temperature. 5. Prepare an ice/water bath in an appropriately Claisen Adapter sized beaker (large enough for the reaction flask to fit into). 6. Add a solution of bromobenzene (2.1 mL, 19.9 mmol) in dry ether (10 mL) through the separatory Reflux Condenser funnel. The reaction may need to be cooled or warmed to maintain a gentle reflux. You may warm the reaction mixture by using a hot water bath (start with a beaker of hot tap water, which may be further warmed with one of the hot water baths in the lab). DO NOT USE A HOT PLATE!!!! FIRE HAZARD. 100 mL Round Bottom Flask 7. Once the reaction has started, and there is a gentle reflux, add 7 mL ether through the separatory funnel. 8. Once the Grignard Reagent has completely formed (this may take up to one hour), it must be used immediately. Add a solution of 2.4 g (13.2 mmol) of benzophenone in 9 mL dry ether through the separatory funnel SLOWLY! The reaction may need to be cooled or warmed to maintain a gentle reflux. 9. After the spontaneous reflux has subsided, heat the reaction mixture with a hot water bath for 15 min. This is a good stopping point. You may disassemble the apparatus, and stopper the flask containing the reaction mixture. 10. (Week 2) Follow the procedure for the HYDROLYSIS, EXTRACTION and CRYSTALLIZATION found in Experiment 33A (Triphenylmethanol) of the laboratory text.