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A Friedel-Crafts Acylation Reaction
Typology: Lab Reports
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Relevant Sections in the text (Wade, 7th^ ed.)
The EAS reaction you will be performing is a Friedel-Crafts acylation, where the electrophile is an acylium ion (R-C≡O+). This reactive ion is formed by the reaction of an acid chloride (acetyl chloride, CH 3 CO-Cl) with aluminum chloride (AlCl 3 ) acting as the Lewis acid catalyst (see Scheme 2). R O Cl
The unknown is one of the following: A (MW = 92.1, density = 0.867 g/mL), B (MW = 108.2, density = 0.996 g/mL), C (MW = 106.17, density = 0.867 g/mL) or D (MW = 120.2, density = 0.864 g/mL). Remove the ice bath after the addition is complete and bring the flask to room temperature. Stir for another 15 minutes and then slowly pour the contents (while stirring) into about 25 g of ice and 15 mL of conc. HCl in a large beaker. PART B: PURIFICATION AND ANALYSIS After transferring the solution to a separatory flask, the organic layer is collected. The aqueous layer is extracted 2 x 20 mL of dichloromethane, CH 2 Cl 2. Combine the organic layers and wash with 2 x 50 mL of saturated aqueous sodium bicarbonate (NaHCO 3 ). Dry the organic layer over anhydrous MgSO 4 and gravity filter the drying agent, collecting the product in a tared round bottomed flask. Remove the CH 2 Cl 2 by rotary evaporation. Weigh the crude product. Obtain an IR spectrum of your product. Also prepare an NMR sample of your product using deuterated CDCl 3 as a solvent and give it to your TA properly labeled. Review the procedures from experiment 3 in Chem 2 2 73a if necessary. If your product is a solid, make sure to obtain a melting point. Run a TLC plate of your crude product directly against your unknown aromatic on the same TLC plate, using 2:1 petroleum ether: ethyl acetate as the eluent. Visualize with UV and iodine. If your sample is a solid, get a melting point. You will have to work up your 1 H and 13 C NMR data and analyze it. Obtain an accurate integration of your (^1) H NMR spectrum, including any “impurities”. If you suspect that your product is contaminated with starting material, carefully integrate the starting material peaks separately so you can calculate an approximate percent of each.
After determining the identity of your unknown aromatic draw the reaction equation showing the structures of starting material and possible products. Name the compounds using IUPAC rules: Calculate your yield: Acetyl chloride: Molecular Weight = _____________ Grams used = _______________ Volume used = _______________ Moles used = ________________ Unknown Aromatic (___): Molecular Weight = _____________ Grams used = _______________ Volume used = _______________ Moles used = ________________ Limiting reagent? ________________ Product: Molecular Weight = _______________ ( hint: MW of your unknown + 42 ) Moles Expected = _______________ Grams expected = _______________ ( theoretical yield ) Mass of round bottom flask and stopper = _______________ Mass of round bottom flask, stopper and products = _______________ Net Mass of products obtained = _______________ Percentage Yield: = _______________ ( Show calculations on reverse )
Analysis of NMR Spectrum of Product: Attach your NMR spectra to this Data Sheet. Assign a structure of your product by completely analyzing your 1 H and 13 C NMR spectra. In some cases it may be possible to see more than one of the disubstituted benzene products. Be sure to integrate all peaks and assign a relative proportion of the products.
Analysis of Infrared Spectrum: Attach and analyze the IR spectrum of your products, assigning appropriate peaks. Compare and comment on it compared to the IR spectrum of the starting material (provided in the laboratory). Also use Table 1 in experiment 4 to try to determine (confirm) the substitution pattern of your product ( ortho, meta or para ).