Question

The intermediate formed in the preparation of phenol by sodium benzene sulphonate is:
A.Sodium prop oxide
B.Sodium phenoxide
C.Sodium ethoxide
D.None of these

Answer 1

Hint: Basically, phenol is an aromatic compound with general formula ${C_6}{H_6}O$ .It is a white crystalline solid and is soluble in water. These can further be prepared from sulphonic acids also known as alkali fusion of sodium benzene sulphonate and from diazonium salts. So, to solve this question we need to know the preparation from sulphonic acids.

Complete step by step answer:
Phenols are organic compounds that contain at least one OH group which is directly attached to the benzene ring. We have three types of phenols depending upon the number of hydroxyl groups attached to the benzene ring. These are monohydric, dihydric and trihydric phenols. Further the monohydric phenols are the simplest members of the series which are commonly known as phenols, dihydric are three isomeric dihydroxy benzenes namely resorcinol, quinol whereas trihydric are known by the common names like hydroxyquinol etc.
Now, phenols can be synthesized by two methods. These two methods are:
1.From sulphonic acid or by alkali fusion of sodium benzene sulphonate- In this process, sodium benzene sulphonate is fused with sodium hydroxide at 573k to produce sodium phenoxide which further yields phenol. The reaction is as shown:
 ${C_6}{H_5}S{O_3}Na + 2NaOH\xrightarrow{{573K}}{C_6}{H_5}ONa + N{a_2}S{O_3} + {H_2}O$
 $2{C_6}{H_5}ONa + 2HCl \to 2{C_6}{H_5}OH + 2NaCl$

2.From diazonium salts- When the diazonium salt solution is steam distilled or is added to dil. ${H_2}S{O_4}$ , it forms phenol. The reaction is as shown:
${C_6}{H_5}{N_2}Cl + {H_2}O\xrightarrow[{{H_2}S{O_4}}]{\Delta }{C_6}{H_5}OH + {N_2} + HCl$
So, we have seen that the intermediate formed in the preparation of phenol by sodium benzene sulphonate is sodium phenoxide.
Hence, option B is correct.

Note: Phenol is very cheap and it has plenty of small-scale applications. Its derivatives are used in cosmetics preparation like sunscreens, skin toners etc. It is also a part of industrial paint strippers used for the removal of epoxy, polyurethane and other coatings in the aviation industry.