Organic Chemistry: Basic Principles and Techniques - Purification of Organic Compounds

Sublimation: A process used to separate substances that transform directly from solid to vapor state upon heating. Examples include $I_2$, $Camphor$, and $Naphthalene$.

Crystallization: Based on the difference in the solubilities of the organic compound and its impurities in a suitable solvent. The impure compound is dissolved in the minimum amount of hot solvent to form a saturated solution.

Simple Distillation: Used for liquids that are stable at their boiling points and contain non-volatile impurities or have a boiling point difference of more than $30-50^\circ C$. Example: Separating $C_6H_5NH_2$ (Aniline, $B.P. 457 K$) and $CHCl_3$ (Chloroform, $B.P. 334 K$).

Fractional Distillation: Employed when the boiling point difference between two liquids is small (less than $25 K$). A fractionating column is used to provide multiple cooling and heating surfaces.

Distillation under Reduced Pressure (Vacuum Distillation): Used for liquids that decompose at or below their normal boiling points. By reducing the external pressure, the liquid boils at a lower temperature. Example: Purification of $Glycerol$.

Steam Distillation: Applied to separate substances which are steam volatile and immiscible with water. The total vapor pressure is $P = P_w + P_o$, where $P_w$ is the vapor pressure of water and $P_o$ is the vapor pressure of the organic liquid.

Differential Extraction: Based on the Nernst Distribution Law, where a solute distributes itself between two immiscible solvents (typically water and an organic solvent like $C_2H_5OC_2H_5$).

Chromatography: A technique based on the differential rate of movement of components of a mixture through a stationary phase under the influence of a mobile phase. It includes Adsorption Chromatography (Column and TLC) and Partition Chromatography (Paper).