Esterification

What is esterification?

The chemical reaction that takes place during the formation of ester is called esterification. Ester is obtained by an esterification reaction of an alcohol and a carboxylic acid.

Esterification

Esterification – Reaction

What is esterification reaction?

When primary alcohol is treated with carboxylic acid in the presence of sulfuric acid a compound is formed. This compound has a sweet smell. The compound obtained is called ester. The chemical reaction occurring in the formation of ester is known as esterification reaction.

CH3COOH + CH3CH2COOH → CH3COOCH2CH3

Esterification Mechanism

This process involves five steps. We have discussed the steps below:

Step 1: Cation formation

Esterification_Mechanism_step_1

Step 2: Delocalized carbocation

Carboxyl oxygen gets protonated to give delocalized carbocation making the carbocation a better electrophile.

Esterification_Mechanism_step_2

Step 3: Transfer of proton

A proton is transferred to one of the hydroxyl groups to form a good leaving group.

Esterification_Mechanism_step_3

Step 4: Formation of pi bond

The hydroxy group’s alcohol oxygen atom donates a pair of electrons to carbon atom which makes a π bond by eliminating water. The concentration of water is less than methanol, therefore, it is not a feasible nucleophile to reverse the reaction.

Esterification_Mechanism_step_4

Step 5: Ester formation

Esterification_Mechanism_step_5

Esterification methods

Esterification can happen in three ways. They are discussed below:

  • From acid anhydride and alcohol
  • From acid chloride and alcohol
  • From carboxylic acid and alcohol

1. Acid anhydride and alcohol

The reaction between alcohol and acid anhydride is comparatively slower when compared to acid chloride. To get a number of esters it is required to warm the mixture. For instance, consider 2,6-diiodophenol.

2,6-diiodophenol reacts with acid anhydride to form ester.

Acid anhydride and alcohol

 

2. Acid chloride and alcohol

Esterification process can also be performed with alcohol and acid chloride at room temperature. Ester is obtained with steamy acidic fumes of hydrogen chloride. For instance, benzoyl chloride.

Reaction of alcohol and benzoyl chloride to form ester.

Acid chloride and alcohol

3. Carboxylic acid and alcohol

Production of esters from carboxylic acid and alcohol. Heat them in the presence of acid catalyst such as sulfuric acid (H2SO4) is used as a catalyst. Example, reaction of ethanoic acid and propanol to form propyl-ethanoate and water.

Carboxylic acid and alcohol

Properties of esters

  • The name of an ester is derived from its carboxylic acid that takes part in the esterification reaction.
  • They have a pleasant smell.
  • They have a wide application in perfume and food industries.
  • Esters are organic compounds found in oils and fats.

Uses of esters

Some common uses of esters are mentioned below:

  • Esters that have fragrance are used in perfumes, food flavourings, and cosmetics.
  • Used as an organic solvent.
  • Nitroglycerin is known and famous for its explosive properties.
  • In the manufacturing of surfactants like detergents and soaps.
  • Natural occurring esters are present in pheromones
  • The backbone of DNA molecules is formed by phospo esters.
  • Polyesters are used in the production of plastics

Frequently asked questions:

1. Give two examples of ester.

Ans: CH3COOCH3 and CH3CH2CH2CH2OH

2. Which compound has a higher boiling point: CH3COOCH3 or CH3CH2CH2CH2OH? Why?

Ans: CH3CH2CH2CH2OH due to the presence of intermolecular hydrogen bonding.

3. Give two main uses of esterification reaction.

Ans: The two major uses of esterification reaction are:

1. Manufacturing of medicines.

2. Manufacturing of paints and dyes.

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