Step 1 : Understanding the Question:
The topic of this question is Named Organic Reactions involving Phenols. Phenols are highly reactive toward electrophilic aromatic substitution due to the strongly activating $-OH$ group. There are several famous named reactions that introduce different functional groups onto the phenol ring. The question describes a specific reaction using chloroform and sodium hydroxide to produce an aromatic aldehyde and asks us to identify the name of this process.
Step 2 : Key Formulas and approach:
The approach is to match the reagents and products to known named reactions:
1. Phenol + Chloroform ($CHCl_3$) + $NaOH \rightarrow$ Salicylaldehyde ($o$-hydroxybenzaldehyde).
2. Identify the active intermediate: Dichlorocarbene ($:CCl_2$).
3. Distinguish from similar reactions: For example, using $CO_2$ instead of $CHCl_3$ would lead to a different reaction.
Step 3 : Detailed Explanation:
The reaction described is the Reimer-Tiemann Reaction. It is a classic method for the ortho-formylation of phenols.
In the first step, Chloroform ($CHCl_3$) reacts with the base ($NaOH$) to produce a highly reactive, neutral electrophile called dichlorocarbene ($:CCl_2$).
This dichlorocarbene attacks the electron-rich phenoxide ion (formed by phenol and $NaOH$) at the ortho position.
After subsequent hydrolysis of the intermediate and final acidification, a $-CHO$ (formyl) group is successfully attached to the ring, producing Salicylaldehyde.
Let's evaluate the other options:
- Kolbe's Reaction (Option A) uses $NaOH$ and Carbon Dioxide ($CO_2$) to produce Salicyllic Acid (not an aldehyde).
- Rosenmund Reduction (Option C) involves the hydrogenation of acyl chlorides to aldehydes using a poisoned catalyst.
- Friedel-Crafts Acylation (Option D) uses acyl halides and $AlCl_3$ to add ketone groups to an aromatic ring.
Since the reagents are $CHCl_3$ and $NaOH$, the reaction is uniquely identified as the Reimer-Tiemann Reaction.
Step 4 : Final Answer:
The introduction of a formyl group using chloroform and alkali is known as the Reimer-Tiemann Reaction. The correct option is (B).