To purify acetanilide by a recrystallization procedure.
a) Describe how you would decide what solvent to use in order to accomplish this objective.
b) How you would calculate the effeciency of your recrystallization procedure with respect to;
--- Improvement in purity across the procedure.
---- Yield efficiency.
Thanks!
You must know how to do parts of this or have some ideas about how to proceed. Let's hear your thoughts and a rationale for why you have those thoughts.
a) To decide on the solvent to use for recrystallizing acetanilide, you would need to consider several factors:
1. Solubility: The solvent should have low solubility for acetanilide at low temperatures, but high solubility at higher temperatures. This allows the impurities to dissolve while the desired compound remains insoluble during cooling, leading to crystal formation.
2. Selectivity: The solvent should selectively dissolve the impurities, leaving acetanilide behind. This ensures that the impurities are removed during the recrystallization process.
3. Chemical compatibility: The solvent should not react with acetanilide or form any undesired products that could affect the purity of the final product.
Some commonly used solvents for recrystallization of organic compounds like acetanilide include water, ethanol, methanol, and ethyl acetate. You can perform a solubility test by adding small amounts of acetanilide to test tubes containing each solvent and heating them. Observe which solvent dissolves the least amount of acetanilide at room temperature and dissolves the most upon heating. This would indicate the most appropriate solvent for recrystallization.
b) To calculate the efficiency of your recrystallization procedure, you can assess the improvement in purity and yield efficiency.
1. Improvement in purity: Measure the purity of the acetanilide before and after recrystallization using a suitable analytical technique like melting point determination or spectroscopy. Melting point can be a good indicator of purity, as impurities often lower the melting point. The closer the post-recrystallization melting point is to the literature value, the higher the improvement in purity.
2. Yield efficiency: Calculate the yield efficiency by comparing the mass of the purified acetanilide obtained after recrystallization to the mass of the impure starting material used. Ideally, the yield should be close to 100% with minimal loss during the recrystallization process. Yield efficiency can be calculated using the following formula:
Yield Efficiency = (Mass of purified acetanilide obtained / Mass of impure acetanilide used) x 100%
By evaluating the improvement in purity and yield efficiency, you can assess the effectiveness of your recrystallization procedure.