Synthesis Of Acetanilide Lab Report

Falak Mdahi
Chem 203.2

The Synthesis of Acetanilide from Acetic Anhydride and Aniline
Introduction
Recrystallization is a technique used to purify solids that contains small amounts of impurities. It is used to isolate pure solids from a supersaturated solution leaving the impurities in the solvent (1). The solid containing the impurities is placed in a hot solvent and upon cooling the compound precipitates to its purified form while the impurities are left behind in the solvent (1). There are six steps when it comes to undergoing a recrystallization of a solid. The first step is choosing a suitable recrystallization solvent. This step is crucial when it comes to executing a successful recrystallization experiment. Solubility comes into play
A mixture of 2 mL aniline, 15 mL deionized water and 3 mL acetic anhydride were stirred. After thirty minutes the reaction was complete and the product was completely precipitated out of the solution. Vacuum filtration was used to isolate the crude acetanilide using a 125 mL filter flask and porcelain Büchner funnel. The product was then washed with 2 mL of ice water and left to dry for about twenty minutes. The observed melting point for the crude acetanilide was 114.3 °C - 115.7 °C. The second procedure dealt with 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 the acetanilide were water, ethanol, dichloromethane and hexanes. If the solid dissolved in the solvent at room temperature then it was too soluble and that solvent could be eliminated. The acetanilide completely dissolved in ethanol and dichloromethane, therefore eliminating them from being the suitable solvent. If the solid did not dissolve in room temperature then it was placed in the sand bath and left to boil. If the solid dissolved, 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 as the crystals came out once placed in the ice bath. The
The obtained NMR spectra was very similar to that of the predicted results. The methyl hydrogen group had a single peak at 2.153 ppm. The results were a little off from the predicted shift of 2.2 – 2.9 ppm but not by much. Next in the spectra, were the hydrogens in the aromatic ring with a range of 7.065-7.436 ppm consisting of multiple peaks, these also matched up to the predicted shift of 6.5-8.0 ppm. The last signal belonged to that of the hydrogen in the amide that had a peak at 7.571 ppm which is well in the range of the predicted shift it 5.0 – 9.0 ppm. Overall the NMR proved that the purified acetanilide had very little impurities shown in the