Friedel-Crafts Alkylation of Benzene

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Chapter 29 Friedel-Crafts Alkylation of Benzene
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Purpose

• In this experiment a mixture of benzene and alkyl
  chloride is treated with AlCl3 (Lewis acid). The
  dialkyl product is isolated by adding water and
  extracting.
• The organic phase is then washed, dried and
  evaporated to give an oily product which should
  solidify upon cooling. You may also use filtering
  paper to absorb any oil from the solid product.

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Reaction Mechanism

• The Friedel-Crafts alkylation is a typical
  electrophilic substitution reaction. The
  electrophile is t-butyl cation generated by the
  reaction of alkyl halide and Lewis acid. The
  dialkyl product is formed stepwise.

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Mystery Modification

• Shown product can be obtained in case of using
  excess of t-Butyl Chloride (at least 5 mmols per
  1 mmol of benzene) under the same reaction
  conditions. You should provide a reasonable
  reaction mechanism in your lab report.

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Comments

• Follow pp. 438-440 (microscale).
• Follow the lab handout for all experimental
  procedures.
• AlCl3 is highly hydroscopic and looses catalytic
  activity after absorbtion moisture from the air.
  Keep it AWAY from prolong contact with air!
• Perform GC/MS and optionally IR analysis of the
  products from both reactions.
• Prepare samples of the products in CDCl3 for NMR.
• Calculate yields. Moderate yields should be
  achieved.
• (Moles Product / Moles Starting Material) x 100
  Yield

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Safety

• Benzene is highly flammable, irritating to eyes
  and skin and may cause lung damage if swallowed.
  Also, as shown on animal models, may cause cancer
  and inheritable genetic damages by prolonged
  exposure. Do not swallow, do not inhale and avoid
  contact with eyes and skin. Wear gloves and
  handle with extreme caution.
• Aluminum chloride is corrosive, wear gloves and
  handle with care.
• Again wearing rubber gloves is absolutely
  necessary during this lab! You will work with
  toxic, carcinogenic and corrosive compounds.