In recrystallization, oiling out occurs when the desired compound has a large impurity with it. Simply put, oiling out is when the product separates not as crystals, but as a liquid "oil".
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In recrystallization, "oiling out" refers to the process of adding a solvent in small amounts to dissolve a minor impurity that is not removed by filtration. The impurity will separate out as an oil layer, which can then be decanted or removed before allowing the remaining solution to undergo crystallization.
Recrystallization is used to purify solids by dissolving them in a solvent and then allowing them to reform into crystals. This process helps remove impurities and improve the overall quality of the solid.
Chloroform is not a commonly used solvent for recrystallization of acetanilide. It is more commonly used for dissolving non-polar or slightly polar compounds. In the case of acetanilide, solvents such as ethanol or ethyl acetate are often preferred for recrystallization.
An Erlenmeyer flask is preferred over a beaker for recrystallization because its conical shape allows for better control of evaporation and minimizes the loss of solvent during the process, leading to more efficient and effective recrystallization.
The product formed from recrystallization can be contaminated with impurities if they are more soluble in the solvent used for recrystallization compared to the desired compound. In this case, the impurities will remain in the solution while the desired compound forms crystals, leading to impurity inclusion in the final product. Proper choice of solvent and recrystallization conditions can help minimize impurity contamination.
A good recrystallization solvent should have the following characteristics: high solubility for the compound being purified at high temperatures, low solubility at low temperatures to allow for crystal formation, non-reactive with the compound, and easily removable from the crystals after recrystallization.