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216 H W10-experiment 1 - Experiment 1 Friedel-Crafts...

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Experiment 1: Friedel-Crafts Acylation Background: Goals: a) work with water-sensitive reagents; b) design experimental procedure and work-up; and c) to assess the procedural design. Electrophilic aromatic substitution reactions take place between the nucleophilic π electrons of an aromatic ring and a strong electrophile. The intermediate carbocation rapidly loses H + to reform the aromatic system. In the case of Friedel-Crafts acylation, the electrophile is an acylium ion, formed by the reaction of an acid chloride with aluminum chloride. The mechanism is shown in Figure 1. H 3 C O Cl Al Cl Cl Cl H 3 C C O + H 3 C C + O + + AlCl 4 - CH 3 C O + C + (1) (2) (3) H O CH 3 H C + H O CH 3 H Cl Al Cl Cl Cl - O CH 3 + HCl + AlCl 3 Figure 1: Mechanism for Friedel-Crafts Acylation You will be assigned either toluene (methylbenzene), ethylbenzene, or anisole (methoxybenzene) to acylate. The reaction is one that comes out of your organic chemistry textbook, so no procedure is available. What variables should you consider when planning your reaction?
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The three starting materials that you want to try: Reactants Products anisole C 6 H 5 OCH 3 Liquid bp 154 4’-methoxyacetophenone CH 3 OC 6 H 4 C(O)CH 3 Liquid bp 154/26 mm Hg ethylbenzne CH 3 CH 2 C 6 H 5 Liquid bp 136 4’-ethylacetophenone CH 3 CH 2 C 6 H 4 C(O)CH 3 Liquid bp 125/20 mm H g toluene CH 3 C 6 H 5 Liquid bp 110 4’-methylacetophenone CH 3 C 6 H 4 C(O)CH 3 bp 226 Scale 0.050 moles reactant anhydrous (anisole, ethylbenzne, or toluene) Group 1: Reaction set up including glassware and stoichiometry . Two things will affect your reaction design: 1) air sensitive reagents anhydrous aluminum chloride and acyl chloride. The reaction between aluminum chloride and acyl chloride is highly exothermic so the rate of reaction should be controlled so that the solutions do not boil.
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