1. Safety precautions:
Safety goggles were worn because methanol solution of 2,4-dinitrtophenylhydrazine and bench dilute sulphuric(VI) acid is corrosive.
The experiment was done away from flame because 2,4-dinitrophenylhydrazine, methanol, ethanol, and many carbonyl compounds are flammable.
2. Sources of error:
The impurities such as pieces of filter paper, excess compound X1, 2,4-dinitrophenylhydrazine might lower the melting point of the derivative. The obtained value might be lower than the value listed in the table given.
3. Suggestions for improvement:
�� The insoluble impurities can be removed by dissolving the solution in ethanol and then being filtered. Then perform recrystallization.
�� The soluble impurities compound X1 and 2,4-dinitrophenylhydrazine might be present in the product before recrystallization. They can be removed in the recrystallization process because of different solubility in ethanol.
4. In selecting a suitable solvent in the recrystallization step, a solvent which the compound X¬ 1 is soluble in when hot and insoluble in when cold should be considered.
5. In the recrystallization procedure, the crystals were dissolved in only the minimum amount of hot ethanol to make the solution achieve saturation so that the yield of product is increased on cooling.
6. If the melting point of the 2,4-dinitrophenylhydrazone is 156℃ we can determine whether the compound X is propanal or pentan-3-one by determining its boiling point.
If the boiling point is 102℃, the compound X should be pentan-3-one;
if the boiling point is 48℃, the compound X should be propanal.
