Lab 9 Report - Friedel-Crafts Alkylation Results and Discussion PDF

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Friedel-Crafts Alkylation Results and Discussion...

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Elizabeth Valcourt CHEM 546.02 Friedel-Crafts Alkylation 28 November 2017 Results and Discussion 1.

This lab produced a white solid 1,4-di-t-butyl-2,5-dimethoxybenzene, from adding alkyl groups (from t-butyl alcohol) to 1,4-dimethoxybenzene. Even though a product was formed, the reaction did not work well. The experimental yield was 0.696 g, which was much higher than the theoretical yield, producing a 128% yield. The product had a lower melting point than what the pure product should have been, indicating that there were impurities in the final product. These impurities may have been unreacted t-butyl alcohol if the solution was not mixed properly. This was identified on the IR spectrum as the broad peak around 3400 cm-1, which indicated an -OH group was present. This reaction was a Friedel-Crafts Alkylation because an alkyl group was added to a benzene ring. Usually, an alkyl halide interacts with aluminum chloride (a catalyst) to form a carbocation (electrophile). However, sulfuric acid was used in this reaction because it could donate a hydrogen to the alcohol to form water, which is a good leaving group. Then the t-butyl alcohol would become a carbocation (electrophile).

Experimental: 1,4-dimethoxybenzene (0.298 g, 0.00216 mol), glacial acetic acid (1 mL), and t-butyl alcohol (0.5 mL) were added to a 10 mL round bottom flask and placed in an ice bath. Sulfuric acid (1 mL) was added dropwise, swirling between drops, and produced a peach colored liquid. The flask was taken out of the ice bath and kept at room temperature for 10 minutes, which

produced a peach solid. The flask was then returned to the ice bath and water (5 mL) was added dropwise, which turned the crystals white. The liquid was removed and the crystals were washed again with water (5 mL). The liquid was removed again and the crystals were washed three times with cold methanol (1 mL). The liquid was removed and the crystals were washed with ethanol (1.5 mL). Vacuum filtration produced white crystals of 1,4-di-t-butyl-2,5dimethoxybenzene (0.696 g, 0.00278 mol, 128% yield, MP: 84-92°C, IR: 2964, 2950, 1504, 1488, 1203, 1035 cm-1)....