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How Carbolic Acid is Prepared from Benzene Sulphonic Acid? - HSC Science (Computer Science) 12th Board Exam - Chemistry

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How carbolic acid is prepared from benzene sulphonic acid?

Prepare carbolic acid from benzene sulphonic acid.

Solution 1

Preparation of Carbolic acid (Phenol) from Benzene sulphonic acid (C6H6SO3H): 

a) When benzene sulphonic acid is neutralised by aqueous sodium hydroxide (NaOH),
sodium benzene sulphonate is obtained.

b) Dry sodium benzene sulphonate when fused with excess of sodium hydroxide at 573K,
sodium phenoxide is obtained along with sodium sulphite (Na2SO3).

c) sodium phenoxide when hydrolysed by heating with dilute sulphuric acid, phenol is
obtained.

When a current of carbon dioxide is passed through aqueous sodium phenoxide, phenol is obtained as product.

Solution 2

From Benzene Sulphonic Acid: Carbolic acid (phenol) is obtained from Benzene sulphonic acid in the following 3 steps

Step- I: Neutralization

Benzene sulphonic acid is neutralized by the addition of dilute NaOH when sodium benzene sulphonate is obtained

Step- II: Fusion at 623 K

Dry sodium benzene sulphonate is fused with the excess of solid sodium hydroxide at about 623 K when sodium phenate (i.e. sodium phenoxide) is obtained.

Step III: Decomposition by dil. H2SO4:

Sodium phenate (Sodium phenoxide) on boiling with dil. H2SO4 is decomposed to form the carbolic acid (or phenol)

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 2016-2017 (March) (with solutions)
Question 8.2 | 7.00 marks
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Solution How Carbolic Acid is Prepared from Benzene Sulphonic Acid? Concept: Phenols - Phenols.
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