Question

Phenol is also called :
A) Salicylic acid
B) Benzyl alcohol
C) Carbolic acid
D) Salol

Answer 1

To solve such questions , we should have knowledge of some basic organic compounds and terms.An acid is any substance which donates proton. Phenol is highly acidic in nature and hence it is also known as carbolic acid.

Complete answer:
Phenol is thought to be similar to alcohols as both have hydroxyl groups attached to it . The difference between alcohol and phenol is that in alcohols the hydroxyl group is attached to the alkyl group and in phenol hydroxyl group is attached to the benzene ring . Phenol is that compound which is formed by the addition of hydroxyl groups in the benzene ring. Let us learn more about phenol and what else it is called.
Acid is not a synonym of a “carboxylic acid”. An acid is a substance that can furnish protons in the solution and hence lowering the pH of the solution . Phenol has the tendency to provide protons in the solution .
Talking about phenols, we know phenols are acidic in nature because the phenoxide ion formed by the loss of electron is resonance stabilized and hence highly stable. Hence , phenols are good acids. Because of their high acidity, phenols are also known as carbolic acids. Phenol acts as a Bronsted acid. Since phenol and carbolic acids are the same . They both have the same molecular formula which is ${C_6}{H_5}OH$ .
There are many ways of preparing carbolic acid. Let us look at one of them.
Preparation:

1. First do chlorination of benzene by reacting it with chlorine gas in presence of either Ferric Chloride or anhydrous Aluminium Chloride or Red phosphorus to get chlorobenzene .
   ${C_6}{H_6} + C{l_2}\xrightarrow{{an.AlC{l_3}}}{C_6}{H_5}Cl + HCl$
2. Then heat the chlorobenzene with steam at $698K$ using calcium phosphate or silica to get the required phenol .
   ${C_6}{H_5}Cl + {H_2}O\xrightarrow{{C{a_3}{{(P{O_4})}_2}/698K}}{C_6}{H_5}OH + HCl$
   This is carbolic acid and this is how it is prepared.

Therefore, from the above equation we can say that the correct answer is (C).

Note: Though phenol and aliphatic alcohols appear to be similar, they are not in various senses. Like for example , the detection test of both phenol and alcohols are different because they react differently with compounds.