What factors influence the selection of a solvent for recrystallization?

The selection of a solvent for recrystallization primarily hinges on the solubility characteristics of both the target compound and any impurities present. An ideal solvent should dissolve the target compound well when hot, enabling it to form a saturated solution at high temperatures, while allowing the compound to crystallize out when cooled. It is equally important that the impurities either remain dissolved in the hot solvent or precipitate out upon cooling, leading to a purer final product.

In this context, the other factors mentioned, such as color, viscosity, and boiling point, do not play a critical primary role in the effectiveness of recrystallization. Color is not relevant to the solubility of compounds; viscosity may affect how the solution is handled but does not impact the solubility dynamics essential for recrystallization. While boiling point can influence the solvent's evaporation rate and how it interacts with the target compound, it is not the sole factor considered, nor does it outweigh the importance of the solubility of both the target compound and any impurities. Therefore, solubility is the cornerstone factor in selecting an appropriate solvent for recrystallization.