0.3 Friedel-crafts reaction  (Page 2/3)

• Reaction of an aromatic compound with an acyl halide and a Lewis Acid

• The electrophile is an acylium ion.

• The para product generally predominates in the acylation of substituted rings.

- Unlike the Friedel-Crafts alkylation, the acylation reaction does not suffer from

rearrangement of the electrophile nor is the product susceptible to further reaction.

- The Freidel Crafts acylation reaction can be used to synthesize alkyl benzenes

indirectly.

Aromaticity of organic compounds:

Although many aromatic compounds are based on the prototypical benzene ring system, many other aromatic compounds are known. In general, aromaticity results from a cyclic, planar, fully-conjugated array of atoms with a total of 4n+2 (n = integer) π electrons. Thus neutral compounds such as pyrrole and furan, as well as charged species such as tropylium, cyclopentadienyl and cyclopropenium ions, all represent aromatic compounds.

Friedel-Crafts acylation of ferrocene

Pre-lab 4: friedel-crafts reaction

(Total 10 points)

Click here for the Pre-Lab

Name(Print then sign): ___________________________________________________

Lab Day: ___________________Section: ________TA__________________________

This assignment must be completed individually and turned in to your TA at the beginning of lab. You will not be allowed to begin the lab until you have completed this assignment.

1. Classify each of the following species as anti-aromatic, aromatic, or nonaromatic.

Support your answer. (3 points)

2. Show the mechanism for the following reaction. Be sure to include all intermediates. (5 points)

3. predict the products from the following reactions. (2 points)

Grading

You will be assessed on:

• Completion of pre lab questions.
• Write-up in your lab notebook
• Completion of report questions.
• TA evaluation of lab procedure.

Materials

Equipment chemicals

• Water bath Ferrocene
• Stir bar Acetic anhydride
• Round bottom flask (10mL) 85% phosphoric acid
• Hirsch funnel 3 M aq NaOH
• Beakers (50, 400 mL) ${\text{NaHCO}}_3$
• TLC plates Hexanes
• Filter paper Toluene, absolute EtOH

Safety

Phosphoric acid and acetic anhydride are corrosive and acetic anhydride is also a lachrymator. Avoid contact or undue exposure to vapor. Wear gloves all the time, especially when you are working with corrosive reagents. Keep safety glasses on all the time. Dispose of organic substances in their proper containers.