Case: Read the passage and answer the following questions

Alcohol can be prepared in many ways. Alcohols are prepared from alkenes by acid catalysed hydration and by hydroboration–oxidation. Alcohols are even prepared from ketones and aldehydes by reduction. The reduction of carboxylic acid and ester leads to the formation of alcohol. Alcohols are produced by the reaction of Grignard reagents with aldehydes and ketones. Phenol, also known as carbolic acid, was first isolated in the early nineteenth century from coal tar. Nowadays, phenol is commercially produced synthetically. In the laboratory, phenols are prepared from benzene derivatives in many ways.

Which of the following reacts with fused NaOH to give phenol?

Chlorobenzene

The correct answer is option 3. Chlorobenzene.

When considering the reaction of halogenated compounds with fused sodium hydroxide \((NaOH)\), the process we are typically looking at involves a nucleophilic aromatic substitution  reaction, which is effective for aromatic halides like chlorobenzene but not for alkyl halides such as chloropentane, chlorohexane, or bromohexane.

Chlorobenzene reacts with fused \(NaOH\) at high temperatures (typically around 300°C) and high pressures to form phenol. The reaction can be summarized as follows:

Why Chlorobenzene Reacts:

Aromatic Halide: Chlorobenzene has a halogen directly bonded to an aromatic ring, which allows for the nucleophilic substitution reaction under the harsh conditions provided by fused NaOH. The electron-rich aromatic ring, under high temperature and pressure, can facilitate the substitution of the chlorine atom by a hydroxide ion, resulting in the formation of phenol.

Other Compounds:

Chloropentane and Chlorohexane (alkyl halides): These compounds do not react with NaOH to form phenol. Alkyl halides can undergo nucleophilic substitution reactions with NaOH to form alcohols, but not phenol.

Bromohexane (an alkyl halide): Similar to chloropentane and chlorohexane, it would not react with NaOH to form phenol but rather form hexanol.

Conclusion: Among the given options, chlorobenzene is the compound that reacts with fused NaOH to give phenol.