Falak MdahiChem 203.2 The Synthesis of Acetanilide from Acetic Anhydride and Aniline Introduction Recrystallization is a technique used to purify solids that contain small amounts of impurities. It is used to isolate pure solids from a supersaturated solution while leaving the impurities in the solvent (1). The solid containing the impurities is placed in a hot solvent and upon cooling the compound precipitates into its purified form while the impurities are left in the solvent (1). There are six steps when it comes to undergoing recrystallization of a solid. The first step is to choose a suitable recrystallization solvent. This step is crucial when it comes to performing a successful recrystallization experiment. Solubility comes into playA mixture of 2 mL of aniline, 15 mL of deionized water, and 3 mL of acetic anhydride was stirred. After thirty minutes the reaction was complete and the product had completely precipitated from the solution. Vacuum filtration was used to isolate crude acetanilide using a 125 mL filter flask and a porcelain Büchner funnel. The product was then washed with 2 mL of ice water and left to dry for approximately twenty minutes. The observed melting point for crude acetanilide was 114.3°C - 115.7°C. The second procedure involved finding a suitable solvent to recrystallize the crude acetanilide. A sand bath was set up and 0.5 ml of each solvent was added to 50 mg of acetanilide in four different test tubes. The four solvents used to test the solubility of acetanilide were water, ethanol, dichloromethane, and hexanes. If the solid dissolved in the solvent at room temperature then it was too soluble and the solvent could be discarded. Acetanilide dissolved completely in ethanol and dichloromethane, thus eliminating them from being the suitable solvent. If the solid did not dissolve at room temperature it was placed in the sand bath and allowed to boil. If the solid melted, it was placed in the ice bath and if crystals were observed coming out of the solution then the suitable solvent was found. The suitable solvent was water since the crystals escaped when immersed in the ice bath. The NMR spectra obtained were very similar to those of the expected results. The methylhydrogen group had a single peak at 2,153 ppm. The results were slightly different from the expected shift of 2.2 – 2.9 ppm, but not by much. Next in the spectra were hydrogens in the aromatic ring with a range of 7.065-7.436 ppm consisting of multiple peaks, these also matched the expected shift of 6.5-8.0 ppm. The last signal belonged to that of hydrogen in the amide which peaked at 7.571 ppm, which is well within the range of the expected shift of 5.0 – 9.0 ppm. Overall, NMR demonstrated that the purified acetanilide had very few impurities