Purification of Organic Compounds

Organic chemistry is the study of carbon-containing molecules’ structure, characteristics, content, reactions, and production. The majority of organic compounds contain carbon and hydrogen, but they may also contain a variety of other elements (e.g., nitrogen, oxygen, halogens, phosphorus, silicon, and sulfur).

Organic chemistry was originally limited to the study of molecules created by living organisms, but it has now expanded to encompass man-made substances.

Methods of Purification of Organic compounds

Various methods used for the purification of complex organic compounds are discussed below in this article.

• Sublimation
• Crystallization
• Distillation
• Fractional Distillation
• Vacuum Distillation
• Steam Distillation
• Differential Extraction
• Chromatography

Sublimation

Conversion of a substance from the solid state to the gaseous state without its becoming liquid. An example is a vaporization of frozen carbon dioxide (dry ice) at ordinary atmospheric pressure and temperature.

Crystallization

Crystallization is a method used for the purification of substances. The separation technique separates solids from a liquid.

The process of turning a liquid substance into a highly structured solid whose atoms or molecules are arranged in a well-defined three-dimensional crystal lattice is known as crystallization. A unit cell is a crystal’s tiniest discrete component. There are millions of these unit cells throughout the crystal.

Distillation

Distillation is the process of selectively boiling a component in a liquid mixture and then condensing it thereafter. It is a method of separation that can be applied to either get more of one particular component out of a mixture or to separate it out almost completely.

Fractional Distillation

Fractional distillation is a type of distillation that involves the separation of miscible liquids. The process involves repeated distillations and condensations and the mixture is usually separated into component parts. The separation happens when the mixture is heated at a certain temperature where fractions of the mixture start to vaporize.

Vacuum Distillation

The boiling point depends on atmospheric pressure; if liquids are distilled in an atmosphere with lower pressure, they will boil at a temperature lower than their boiling points. The vacuum pump is used to do this. Reduced air pressure causes liquids to boil more quickly, which speeds up the entire distillation process.

Steam Distillation

Steam Distillation is a separation process for temperature-sensitive substances. It is an exclusive kind of distillation. Another option is to separate miscible liquid bases based on how volatile they are. an example would be aromatic compounds. It is essential in some industrialized areas. No chemical reaction occurs in this situation

Differential Extraction

Differential extraction is the method of extracting an organic component from its aqueous solution by shaking it with an organic solvent in which it is insoluble.
As an example, consider the separation of an oil-water mixture.

Chromatography

Chromatography is a technique used to separate mixtures. The mixture is passed through another substance, in this case, filter paper. The different colour ink particles travel at different speeds through the filter paper allowing us to see the constituent colours of the pen ink.

Types of Chromatography

Chromatography is of two types:

• Adsorption Chromatography
• Partition Chromatography

Adsorption Chromatography

Adsorption chromatography is a type of chromatography in which the components of a mixture are separated through adsorption.

Adsorption chromatography is one of the oldest chromatography techniques still in use. It employs a mobile phase, which can be either liquid or gaseous, during the process. During the adsorptive process, the mobile phase is adsorbed onto the surface of a stationary solid phase.

Adsorption Chromatography is further classified into:

• Thin Layer Chromatography
• Column Chromatography

Thin Layer Chromatography

Thin-layer chromatography (TLC) separates a mixture of chemicals into their constituents using a glass plate coated with a very thin layer of adsorbent, such as silica gel and alumina, as shown in the image below.

In this technique, the glass plate is used. The solution of the to-be-separated mixture is applied as a small spot 2 cm above one end of the plate and the plate is placed in a closed jar containing an eluant, which rises up the plate carrying various components of the mixture to various heights.

Column Chromatography

Column chromatography, as depicted in the image below, is a technique for separating the components of a mixture using a column of appropriate adsorbent packed in a glass tube. The combination is placed on top of the column, and an adequate eluant is allowed to slowly trickle down the column.

The separation of the components occurs depending on the degree of adsorption of the components on the wall adsorbent column. The component with the highest absorptivity is kept at the top, while the others flow down to various heights

Partition Chromatography

Partition chromatography refers to the chromatography technique that is based on the partitioning of components of a mixture between stationary and mobile phases. It is classified into several types, including paper chromatography, gas-liquid chromatography, liquid-liquid chromatography, and so on.

FAQs on Purification of Organic Compound

Question 1: What is the basic principle of chromatography?

Answer:

Chromatography is based on the idea of separating molecules in a mixture that has been added to the ground or solid and liquid stationary states (stable phase) while travelling with the help of a mobile phase. 

Question 2: What is the Rf value in chromatography?

Answer:

In paper chromatography, RF refers to the distance a fluid component goes up a chromatography plate. All chemicals have a common RF value for each solvent, and RF values are used to match unknown samples with known compounds.

Question 3: What are the four major purifying methods?

Answer:

Four major purifying methods are as follows:

• Filtering
• Crystalline Formation
• Sublimation
• Distillation

Question 4: How can sublimation be used to purify organic compounds?

Answer: 

Sublimation is the process of transforming a solid into a gas without passing through the liquid state. This technique can be used to purify compounds that are sublimable or have vapor pressures that reach atmospheric pressure well before they reach their melting temperatures.