Chemistry 351 Laboratory - Spring Semester 2010

Expt #5. Electrophilic Aromatic Substitution. Friedel-Crafts Acylationof Xylene.

Relevant textbook readings - Lab Manual - Pavia Expt 59, Smith chap 18 (especially 18.5-18.11), Mohrig, Technique 11 (especially 11.3 and 11.6)

Overview - Experiment 59 in Pavia will be carried out essentially as described in the lab manual. (However, the 2008/2009 lab manual gives a "small-scale" procedure that will not be used. We will use the semi-microscale procedure given in the 2009/2010 lab manual. See me for a photocopy of the necessary pages if need be.)

Each group will be assigned one of the three xylene isomers to acylate. Write the prelab assuming it might be any of the three.

The product will be purified by vacuum distillation and characterized using 1H  NMR, IR, and GC-MS.

Procedure Modifications and Notes

  1. Double the scale of the experiment and use a 25-mL round bottom flask.
  2. The AlCl3 should be weighed into a dry screw top vial and the vial immediately tightly capped until use. A balance will be placed in one of the fume hoods for purposes of weighing out this compound.
  3. The acetyl chloride is dispensed by volume in a fume hood into a separate vial, which you will then transport to your hood after capping it tightly.
  4. Because you will be working in an efficient fume hood, no gas trap is necessary. Just connect a reflux condenser to the round bottom flask to act as an air condenser (no water circulation needed). The additions of the acetyl chloride and your aromatic compound should be done through the top of the open condenser. Be aware that the reaction gives off HCl gas, however and that the apparatus should be set well back in the hood and that you need to keep your head out of the hood during the reaction!
  5. Vacuum distillation of the product will be performed using the apparatus shown in Figure 11.20 on p 150 of Mohrig.
  6. The boiling point of the product will not be measured.
  7. You should obtain 1H  NMR and IR spectra of your product. The 1H spectrum will be the most valuable to you in determining the position at which acylation occurred. Also prepare a sample for GC-MS by diluting one drop of your NMR sample solution in 4 mL acetone.

Assigned Questions

  1. Question number 8 in Pavia.
  2. Construct a separation scheme flow chart with branches to show where physical separations occurred. Discuss the separation process referring to this flow chart and identifying the most likely major steps where yield was lost.