Briana Charchafliah Recrystallization 9/25/2015
1. Did recrystallization improve the purity of your acetanilide? How can you tell?
The process of recrystallization improves the purity of a compound by two ways.
Because impurities usually have a different solubility, it will either not dissolve in the
boiling solvent and be filtered out, or the impurities may stay dissolved in the cold
solvent during recrystallization. Another reason that recrystallization improves the purity
of a compound is that if an impurity is present during crystal growth, it will prevent the
crystals from packing in an orderly manner due to its irregular shape. This leads to a less
stable crystal, therefore making it less likely to form.
During the lab, when I was dissolving the acetanilide in the boiling water, I
noticed that there were small brownish pieces at the bottom of the beaker that would not
dissolve no matter how much of the boiling solution I added. The small brownish pieces
are likely impurities, which did not dissolve in the solvent due to the fact that it has a
different solubility than pure acetanilide. The impurities, as a result, were filtered out.
This is one way I can tell my final product of acetanilide was more pure than the starting
acetanilide. I also know that the purity of my acetanilide was improved because my final
melting point range is between 114°C and 116°C, which is very close to the literature
melting point of 114.3°C. Because the melting points are so similar, one can assume that
the final acetanilide is relatively more pure.
