Which of the following compounds will react with sodium hydroxide solution in water? 

C₆H₅OH

The correct answer is option 1. \(C_6H_5OH\).

Let us explore why phenol (\(\text{C}_6\text{H}_5\text{OH}\)) reacts with sodium hydroxide (\(\text{NaOH}\)) and why the other compounds do not.

1. Phenol (\(\text{C}_6\text{H}_5\text{OH}\))

Phenol consists of a benzene ring (\(\text{C}_6\text{H}_5\)) with a hydroxyl group (\(\text{OH}\)) attached to it. Phenol is weakly acidic compared to other acids. The hydroxyl group attached to the benzene ring can donate a proton \((H^+)\) to form a phenoxide ion (\(\text{C}_6\text{H}_5\text{O}^-\)).

Reaction with Sodium Hydroxide:

In this reaction, phenol reacts with sodium hydroxide to form sodium phenoxide (\(\text{C}_6\text{H}_5\text{O}^-\text{Na}^+\)) and water. The phenoxide ion is stabilized by resonance, making phenol slightly acidic.

2. Benzyl Alcohol (\(\text{C}_6\text{H}_5\text{CH}_2\text{OH}\))

Benzyl alcohol has a benzene ring (\(\text{C}_6\text{H}_5\)) with a -CH₂OH group attached. The -CH₂OH group is a primary alcohol group. Benzyl alcohol is not acidic because the hydroxyl group does not have the ability to donate a proton easily. The -CH₂OH group does not ionize to form a negatively charged ion that would react with \(\text{NaOH}\).

Reaction with Sodium Hydroxide: Since benzyl alcohol is not acidic, it does not react with sodium hydroxide.

3. Tert-Butyl Alcohol (\((\text{CH}_3)_3\text{COH}\))

Tert-butyl alcohol has a central carbon atom bonded to three methyl groups and one hydroxyl group. Tert-butyl alcohol is a tertiary alcohol and, similar to other alcohols, does not have acidic protons that can react with sodium hydroxide. The hydroxyl group in tertiary alcohols is not sufficiently acidic to form an ion in the presence of \(\text{NaOH}\).

Reaction with Sodium Hydroxide: Tert-butyl alcohol does not react with sodium hydroxide.

4. Ethanol (\(\text{C}_2\text{H}_5\text{OH}\))

Ethanol is a simple primary alcohol with two carbon atoms and a hydroxyl group.  Like other alcohols, ethanol is not acidic enough to react with sodium hydroxide. The hydroxyl group in ethanol does not donate protons readily.

Reaction with Sodium Hydroxide: Ethanol does not react with sodium hydroxide because it does not have the acidic properties necessary for this reaction.

Summary

Phenol (\(\text{C}_6\text{H}_5\text{OH}\)) reacts with sodium hydroxide due to its slightly acidic nature, allowing it to form a phenoxide ion. Benzyl Alcohol (\(\text{C}_6\text{H}_5\text{CH}_2\text{OH}\)), Tert-Butyl Alcohol (\((\text{CH}_3)_3\text{COH}\)), and Ethanol (\(\text{C}_2\text{H}_5\text{OH}\)) do not react with sodium hydroxide because they are not sufficiently acidic.