Question

Preparation of phenol from benzenesulphonic acid is the example of :
A. Electrophilic substitution reaction
B. Nucleophilic substitution reaction
C. Condensation reaction
D. None of the above

Answer 1

Hint: One of the methods to manufacture phenol synthetically is from benzene sulphonic acid . In the above reaction the $S{O_3}{H^ - }$ group in benzene sulphonic acid is replaced by $O{H^ - }$ group to form phenol.

Complete step by step answer: As we know there are various ways to prepare phenol and one of them is from benzene sulphonic acid .
${C_6}{H_6}\xrightarrow{{oleum}}{C_6}{H_5}S{O_3}H\xrightarrow[{{H^ + }}]{{NaOH}}{C_6}{H_5}OH$
First benzene is sulphonated with oleum to form benzene sulphonic acid which is then fused with $NaOH$ at 623K , in this step $S{O_3}{H^ - }$ is replaced with $O{H^ - }$ (as we can see in the figure ) and phenol is formed .
Now , since $S{O_3}{H^ - }$ is a nucleophile and $O{H^ - }$ is also a nucleophile the above reaction is nucleophilic substitution reaction as the nucleophile is substituted on the aromatic ring .
A nucleophile is an electron rich species and can donate electrons to electron deficient species , hence they are also termed as nucleus loving groups . They are generally negatively charged or neutral with lone pairs of electrons . For example - $S{O_3}{H^ - }$ ,
Whereas an electrophile is an electron deficient species which can accept lone pairs of electrons from electron rich species , they are also known as electron loving species . They are generally positively charged or neutral with empty orbitals . For Example - ${H^ + }$ .

Note:
Basically there are two fundamental events in a nucleophilic substitution reaction:
-formation of the new σ bond to the nucleophile
-breaking of the σ bond to the leaving group .