Expt #3. Friedel Crafts Acylation of Cumene

Relevant textbook reading - Brown and Poon, Chapter 9.6-9.7

Overview - You will react propionyl chloride/AlCl₃ with cumene and use NMR to determine the structure of the obtained product. (The product structure is predictable from the textbook reading assignment.)

Procedures

Running the reaction.

• Using the balance located in the dispensing fume hood, weigh out 11 mmol AlCl₃ into a dry 50-mL round bottom flask.
• Add a small stir bar and 10 mL dichloromethane (DCM).
• Cautiously add 1.0 mL propionyl chloride.
  
• Attach a reflux condenser, Claisen adapter, and addition funnel as shown in Fig 7.4a (p 63) in Mohrig.
• Prepare a solution of cumene (10 mmol) in 5 mL DCM and add this to the addition funnel.
• Add the cumene solution dropwise over a period of approx 5 min to the stirring solution.
• Stir for an additional 30 min.

Work-up procedures.

• Slowly add 7.5 mL cold water via the addition funnel to stop the reaction and quench any left over acyl chloride.
• Place the flask on an ice bath and slowly add 7.0 mL concentrated HCl. At this point all of the aluminum salts should have dissolved. If this is not the case add another 0.5 mL of HCl.
• Transfer the reaction mixture to a separatory funnel and drain the lower layer into a small Erlenmeyer flask. Avoid getting any of the aqueous layer when carrying out this step.
• Extract the aqueous layer with 5 mL additional DCM and combine the organic layer with the previous organic layer.
• Wash the combined organic layers with 5 mL 1% NaHCO₃(aq). Caution, CO₂ gas is liberated here so the separatory funnel will need to be vented early and often.
• Dry the organic solution over Na₂SO₄.
• Use the rotary evaporator to remove the DCM solvent in vacuo.
• Determine the yield.
  

Characterization of Product

• Obtain the ¹H and ¹³C NMR spectrum using CDCl₃ as the solvent.