Chemistry 351 Laboratory - Summer 2012

Expt #4. A Green Friedel-Crafts Acylation: Acetylation of tert-Butylbenzene using ZnO instead of Aluminum Chloride.

Relevant textbook readings - Klein, Chapter 19. Mohrig, Techniques 11 and 15.

Reference for Procedure - Sarvari, M. H.; Sharghi, H. J. Org. Chem., 2004, 69, 6953–6956

Overview - You will acetylate tert-butylbenzene using a procedure adapted from the above Journal of Organic Chemistry reference.

Procedure

  1. We will run the reaction at five times the scale of the literature procedure and use a two-fold excess of acetyl chloride. (5 mmol tert-butylbenzene + 10 mmol acetyl chloride).
  2. Use a 5-mL r.b. flask as the reaction vessel. Stir the reaction mixture for 15 minutes at room temperature.
  3. "Elute" with 50 mL dichloromethane. Do so by rinsing the solid out of the reaction flask repeatedly into a vacuum filtration apparatus. Only leave the vacuum on as necessary to pull the liquid through the Buchner funnel, we do not want to lose all of the solvent to evaporation prematurely.
  4. Transfer the filtrate into a separatory funnel.

For steps 5 and 6, use extreme caution to vent the separatory funnel quickly and often. (See Mohrig Technique 11.2 - 11.4 Extraction Procedures using a Separatory Funnel.)

  1. Wash with 50 mL water. Separate the layers and return the lower organic layer to the separatory funnel for step 6.
  2. Wash with 50 mL aqueous10% NaHCO3.
  3. Dry the organic layer over Na2SO4.
  4. Decant the liquid into a pre-weighed round bottom flask suitable for rotary evaporation. Rinse the drying agent with an additional 5 mL DCM so as to avoid loss of product in this step.
  5. Evaporate off the DCM solvent in vacuo using the rotary evaporator.
  6. Determine the yield of crude product and save a small sample for mp determination.
  7. Recrystallize the product using ethanol as solvent. (See Mohrig Technique 15.4-15.5 - Miniscale Procedure for Recrystallizing a Solid.)
  8. Obtain the mps of the crude and final products as well as the 1H  NMR of the final crystalline product.