Methods of Purification of Organic Compounds

The purification of organic compounds is a necessary step after its extraction from a natural source or its synthesis in the laboratory. The method of purification of the organic compound depends mainly on the nature of the compound and the impurities present. The factors that could be taken into account for selecting a particular method of purification are boiling point, melting point, solubility, etc. the most important method of purification is Chromatography.

Various methods of purification

Let’s have a look at some of the methods in brief.

  • Sublimation:

This method can be applied to only those compounds that change their state directly from solid to vapor on heating. Hence this method can be used for separating the sublimable compounds from the non-sublimable impurities.This process is known as sublimation.

  • Crystallization:

The difference in the solubilities of an organic compound and that of the impurities present in it, in a suitable solvent, is the basis for this method of separation. A concentrated solution is prepared by dissolving the compound in a suitable solvent; the pure compound crystallizes out on cooling. The dissolved impurities are removed through filtration. The filtrate contains some amount of pure compound too. A compound containing impurities of comparable solubilities are purified by repeated crystallization.

  • Distillation:

This method is mainly used for separating liquids with sufficient difference in their boiling points. It can also be used for separating volatile liquids from non-volatile impurities. There are two kinds of distillation methods widely used in the industry for purifying organic compounds. These are:

  • Fractional distillation:

It is the process in which the components of a mixture are separated by heating the chemical mixture. Boiling point plays a vital role in fractional distillation. The component with lower boiling point vaporizes first and then the components with higher boiling points. In this way the components of

  • Steam distillation:

In this method substances which are steam volatile and immiscible with water can be separated. It basically lowers the distillation temperature of the organic compounds which are immiscible with water having a high boiling point.

  • Differential Extraction:

It is used for the separation of organic compound present in an aqueous solution. The compound is removed from the aqueous solution by dissolving the compound in a highly soluble solvent forming a layer with the aqueous solution.The aqueous solution and the organic solvent should be immiscible and are separated using a separatory funnel. Later on, the organic solvent and the compound is separated by evaporation or distillation.

  • Chromatography:

Chromatography is an important separation technique used to separate constituent particles of a mixture of substances, to purify the compounds and check the purity of compounds. In this technique on a stationary phase (solid or a liquid) a mixture of substance is applied. The mixture of gas or the pure solvent is allowed to move slowly on the stationary phase. Due to which the components of the mixture start separating from one another. Chromatography is of two types namely Adsorption chromatography and Partition chromatography.

This was just a glance about the different methods of purification of organic compounds. To know these methods of purification in detail download BYJU’S – The learning app.


Practise This Question

The temperature and pressure at which ice, liquid water and water vapour can exist together are