Ferrocene 2011 - Friedel-Crafts Acylation of Ferrocene...

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Acylation of Ferrocene 2011 1 Friedel-Crafts Acylation of Ferrocene * Pre-Lab Preparation 1. Record MSDS information for acetylferrocene, acetic anhydride and methylene chloride (also known as dichloromethane). 2. A Stoichiometry Table is required in your pre-lab materials; details of required quantities must be obtained from the procedure (it is not necessary to include the phosphoric acid). Use the following reaction for your stoichiometry: H 3 PO 4 Fe + Fe O CH 3 + CH 3 C O O C O CH 3 C O OH CH 3 3. You will have two weeks to complete this experiment, including instrumentation. 4. A formal typed report is required at the completion of this experiment. Please refer to the documents following the procedure for details. The report is due three weeks after the completion of the experiment. 5. Write out the complete mechanism for the acylation of ferrocene using phosphoric acid and acetic anhydride. The mechanism does not need to be in your lab notebook, but it must be drawn (using a computer chemical drawing program) in your typed report. Discussion In this experiment, you will carry out an electrophilic aromatic substitution reaction (S E Ar), specifically a Friedel-Crafts acylation reaction. In all S E Ar reactions, an aromatic ring acts as a nucleophile in a reaction with an electrophile. In Friedel-Crafts acylation, the electrophile is an acyl cation, or acylium ion. The acylium ion is often generated by the reaction of AlCl 3 with an acyl chloride, as shown in the example below, although carboxylic acid anhydrides can also be used. The acylium ion is resonance stabilized, and the resonance structure with the positive charge on the oxygen is particularly important because in this structure both the oxygen and the carbon have complete octets of electrons. O R Cl + AlCl 3 O C R O C R AlCl 4 The electrophilic acylium ion reacts with benzene to form an intermediate benzonium ion. Elimination of a proton from the benzonium ion, facilitated by - AlCl 4 , yields the acylbenzene and regenerates aluminum chloride. * This experiment is a combined adaptation of a procedure from the University of Utah and a procedure written by Dr. Edward Matjeka, BSU Chemistry Professor Emeritus.
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