Melting points and Recrystallisation 1.1 Given that the average recovery for thi
ID: 1021911 • Letter: M
Question
Melting points and Recrystallisation
1.1 Given that the average recovery for this process is ~80%, what would be the most likely reason if a recovery of less than ~50% is obtained?
1. The melting point of your purified sample should be higher and sharper than that of the crude sample. If your recrystallized sample contains an impurity, what is it most likely to be, and why?
2. If you did not know what solvent to use to recrystallize the acetanilide, how would you test a solvent for suitability as a recrystallization solvent?
3. For a recrystallisation to be successful the compound must be sparingly soluble in the cold solvent but readily soluble in the hot solvent. Why?
Explanation / Answer
1.1 ) the average recovery for this process is ~80%, the most likely reason if a recovery of less than ~50% is obtained,is incomplete recrystallyzation of the product means a filteration before complete recrystllyzation.
1) The melting point of your purified sample should be higher and sharper than that of the crude sample. If your recrystallized sample contains an impurity, then the melting point will be less than that of pure one because due to melting point depression.
2) If you did not know what solvent to use to recrystallize the acetanilide, we will test a solvent for suitability as a recrystallization solvent by taking different - 2 solvent like polar or non-polar because polar molecules dissolve in polar solvent vice versa.
3) For a recrystallisation to be successful the compound must be sparingly soluble in the cold solvent but readily soluble in the hot solvent because on heating compound dissolves in the solvent out of which impurities remains soluble even after cooling but as we know that compound is sparingly soluble in cold solvent after colling it recystallizes.