4.4: Experiment 3 Notes
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PURIFICATION OF SULFANiLAMIDE BY CRYSTALLIZATION
The sulfanilamide molecule poses a challenge for crystallization because it contains both polar and nonpolar groups. Because of that, a solvent pair is used that has an intermediate polarity. 95% ethanol is the solvent of choice. Water is present in 5% to provide a highly polar environment that will solvate the polar amino and sulfonamide groups. Ethanol provides the less polar environment that will solvate the nonpolar benzene ring.
Other appropriate solvents of intermediate polarity that might work well are acetone and isopropyl alcohol.
1. When heating on a hot plate, keep in mind that 95% alcohol boils rather fast. Keep an eye on the solvent level and be ready to add more if you lose too much by evaporation. If you lose too much solvent you might burn your sample.
2. Skip the optional exercise on p. 25.
3. Do not do parts B, C, or D.