Uses of Benzoic Acid: Overview, Questions, Preparation

Benzoic acid is an organic compound with the molecular formula C6H5COOH. It is an aromatic carboxylic acid with a carboxyl group attached to a benzene ring. The esters and salts of benzoic acid are commonly known as 'benzoate.’

The physical properties of benzoic acid are as follows:

The molecular structure of benzoic acid is as follows:

The molecule of benzoic acid has seven carbon (C) atoms, six hydrogen (H) atoms, and two oxygen atoms (O). It has a benzene ring attached to a carboxyl group.

There are various methods to prepare benzoic acid. Some of them are as follows:

• From benzene

The most common method to prepare benzoic acid from benzene is by using Friedel Kraft's calculation reaction.

In this reaction, benzene reacts with carbon dichloride (COCL2) to form Benzoyl chloride (C6H5COCl). 

This reaction takes place in the presence of anhydrous aluminum chloride.

The benzoyl chloride then reacts with water to form benzoic acid. It releases hydrochloride in this process.

• From toluene

The most common method to produce benzoic acid commercially uses toluene and oxygen.

Toluene undergoes partial oxidation due to oxygen to give benzoic acid. This chemical reaction uses manganese or cobalt naphthenates as catalysts. 

• Benzoic acid can be used in a variety of industries. Some of them are as follows:

• Benzoic acid is used as a food preservative in different foods like soft drinks, salad dressings, and pickles. It prevents the growth of bacteria and yeast in food and helps increase their shelf life.

• Benzoic acids serve as a starting material for the development of plasticizers. Methyl benzoate undergoes transesterification to produce plasticizers like glycol esters.

• It also serves as the precursor for the formation of Sodium benzoate. Sodium benzoate helps in the lowering of glycine levels in our body.

• Benzoic acid is present in ointments used for treating various bacterial and fungal infections.

• It is also used in the production of various cosmetics, mouthwashes, toothpaste, and face cleansers.

• It also acts as a germicide and helps in treating urinary tract infections and bronchitis.

• It was commonly used as an antiseptic and as an expectorant by doctors in the 20th century.

• Recent studies show that benzoic acid may also be effective in preventing the growth of coronavirus in the body.

In class 12, chapter Aldehydes, ketones, and carboxylic acids provide information about benzoic acid. The chapter consists of the various properties of this compound and its uses. The chapter further explains the different methods of preparing benzoic acid and its reactions with other compounds.

Aldehydes, ketones, and carboxylic acids carry a weightage of 6-8 marks in the exam. Hence, one or two questions based on benzoic acid may be asked.

[Image courtesy: NCERT]

Q: What is the crystal structure of benzoic acid?

Q: What is the refractive index of benzoic acid?

Q: Can we produce benzoic acid using hydrolysis?

Q: Is benzoic acid dangerous?

Q: What are the different reactions that benzoic acid can undergo?