Chemistry 340 at Winona State University – Professor Thomas Nalli
Experiment #4. Electrophilic Aromatic Substitution. Part 2 – Purification and Analysis of Crude Product
In this part of the lab, crude product mixtures from Part 1 will be analyzed by 1H NMR and GC/MS. The crude products will be purified by recrystallization or distillation.
Purification Procedures
References for Techniques. (Look at the Macroscale sections in the Lehman textbook)
Recrystallization. pp 130-138 operation 25.
Gravity Filtration, pp 61-63 operation 12
Vacuum Filtration. pp 65-68 operation 13.
Simple Distillation. pp 152-153 Figs E7,E8,E9; 158-159, operation 27
Fractional Distillation. pp 181-185, operation 29
Nitration of bromobenzene/iodobenzene. Recrystallize the product from 95% ethanol. Safety: Ethanol is flammable. Use a hot water bath as the heat source for the recrystallization.
Nitration of methyl benzoate. Recrystallize the product from methanol. Safety: Ethanol is flammable. Use a hot water bath as the heat source for the recrystallization.
Butylation of phenol. Recrystallize the product from petroleum ether (bp 60-90ºC). Safety: Petroleum ether is flammable. Use a hot water bath as the heat source for the recrystallization.
Butylation of tert-butylbenzene. Recrystallize the product from methanol. Safety: Ethanol is flammable. Use a hot water bath as the heat source for the recrystallization.
Propylation of p-xylene. This product will be purified by distillation. Decant the product solution from the drying agent into a 25-mL round bottom flask. Add a stir bar, clamp the flask up and assemble a fractional distillation apparatus (see figure on p 181). Use a heating mantle and Variac as the heat source. Make sure that all of the joints are air-tight (use the yellow joint clips) and then begin heating. Distill out the excess p-xylene by distilling until the boiling temperature reaches 180ºC. Stop heating, allow the distilling flask to cool enough so that vapors are no longer refluxing in the column, then remove the column and the condenser and reassemble the apparatus for short-path distillation (see Fig E9 on p 153). Heat and collect the initial distillate with bp below 180ºC in the original receiving flask (it’s more xylene!). Change the receiving flask to a small pre-weighed flask and continue distilling collecting the product in the in the 180 to 207ºC range. Safety: The heating mantle will be very hot!
Bromination of toluene. Decant the ether solution from the drying agent into an appropriately sized round bottom flask. Use a rotary evaporator to remove the solvent. (The instructor will assist.) This will leave your crude product. Crystallize the product from 95% ethanol. Safety: Ethanol is flammable. Use a hot water bath as the heat source for the recrystallization.