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.) |