Experiment #6 - Preparation of 4-Acetylbiphenyl 

References:

Smith, Chapter 26.2, Mohrig, Techniques 11 and 12. Chapter 21.1-21.3, 22.1-22.3

Overview. You will use a microwave-assisted Suzuki reaction to prepare 4-acetylbiphenyl from 4-bromoacetophenone and phenylboronic acid (eq 1). A balanced version of the equation is also shown (eq 2).

Running the Reaction. Place 1.0 mmol each of phenylboronic acid, 4-bromoacetophenone, and tetrabuylammonium bromide (TBAB) in a glass microwave reaction vessel. Add 3.0 mmol of Na₂CO₃, 0.004 mmol of palladium acetate, and 2.0 mL of distilled water. Add a small teflon-coated magnetic stir bar and then seal the vessel using the provided screw cap to the proper torque using the provided torque tool. Label the vessel with a Sharpie and then place it in the microwave carousel noting its position. Once all student teams have completed this step, the instructor will demonstrate the operation of the microwave reactor and set it up to heat the reaction mixtures to an internal temperature of 150° C and hold it there for 5 min. Once the reaction mixture has cooled to near 50° C then it can be opened and the work up commenced.

Work Up Procedures. Transfer the reaction mixture into a separatory funnel, washing the vessel with 30 mL ethyl acetate and using a spatula to scrape out any remaining solid from the vessel into the sep funnel. Add 30 mL water and then stopper the sep funnel and shake the contents with frequent venting. (Mohrig Technique 11). The organic layer should then be washed in the sep funnel with 30 mL of NaCl(sat) and, after final separation of the layers, dried over sodium sulfate (Mohrig Technique 12). Decant the dried liquid into a pre-weighed round bottom flask. Use a rotary evaporator (Mohrig p 140) to evaporate off the ethyl acetate solvent leaving the product. Weigh the flask and determine your yield and percent yield and make sure to record both in your notebook.

Characterization of the Product. Obtain the mp range and C-13 and proton NMR spectra.

Product Submission - Submit the product in a fully labeled 2"x2" ziploc bag. (See the lab report guidelines for how to label.)