Recrystallization lab, 1.Appearance of pure sulfanilamide after crystallization

Question

Recrystallization lab,

1.Appearance of pure sulfanilamide after crystallization (color,shape and approximate size of crystals)?

2. Based on the appearance of sulfanilamine before crystallization, do you think it is pure? Explain.

Name Recrystallization OBJECTIVES loc Purify an impure of an antibiotic Practice the crystallization technique. INTRODUCTION The purpose of this experiment is to introduce the technique of very common procedure used to purify crude in the laboratory. The a to be crystallized in general technique involves dissolving the a hot solvent and cooling the solution slow decreased solubility at lower temperatures and will separate from The dissolved material has is called crystallization if the solution as it is cooled. This phenomenon and nonselective. the crystal growth is relatively slow and selective or precipitation if the process is rapid crystallized, Since the impurities are usually present in much smaller amounts than the compound being substance most of the impurities will remain dissolved in the solvent even when it is cooled. The purified can then be separated from the solvent and impurities by filtration n this experiment, you will carry out a crystallization of impure sulfanila mide using 95% ethyl alcohol as the solvent. Sulfanilamide is one of the sulfa drugs, the first generation of antibiotics to be used in successfully treating many major diseases such as malaria, tuberculosis, and leprosy Sulfanilamide The solubility of sulfanilamide in 95% ethyl alcohol is given in the following table Temperature Solubility (mg/mL) 40°C 46 60°C Notice that the solubility increases significantly as the temperature increases. Therefore, 95% ethyl alcohol is an ellent solvent for crystallizing A graph of this is shown on the next page You will Crystallize a sample of impure sulfanilamide by dissolving it in the minimum amount of boiling 95% ethyl alcohol and then cooling the solution, first to room temperature, and then to o oc in an ice-water bath The purity of the final material after crystallization will be determined by observing the color of your crystals and by performing a melting point on your sample. You will also weigh your sample and calculate the percent recovery. It is not likely that you will obtain a 100% recovery. This is true for several reasons: experimental loss, the original sample is not 100% sulfanilamide, and some sulfanilamide is soluble in the solvent even at 0 °C. Because of this latter factor, some sulfanilamide will remain dissolved in the mother liquor (the liquid remaining after crystallization has taken place)

Explanation / Answer

Recrystallization of sulfanilamide

1) Based on the color of the crystal the recyrstallized sulfaniliamide is pure.

2) However, the melting point is slightly lower than the literature melting point and may have some of the leftover solvent in it which has reduced the melting point of the recovered or recrystallized sulfanilamide. Drying the material further would remove this solvent and make the crystals pure.

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