Reimer-Tiemann Reaction (Synthesis of Salicylaldehyde)

$$\text{Phenol} + \text{CHCl}_3 + 3\text{NaOH} \xrightarrow{340\text{K}} \text{Salicylaldehyde (Major)} + 3\text{NaCl} + 2\text{H}_2\text{O}$$

Concept: Phenol reacts with chloroform ($\text{CHCl}_3$) in the presence of an aqueous alkali ($\text{NaOH}$ or $\text{KOH}$) to introduce a formyl group ($$\text{--CHO}$$) onto the aromatic ring, yielding 2-hydroxybenzaldehyde (salicylaldehyde) as the major product. The reaction proceeds via an electrophilic aromatic substitution involving a neutral, highly reactive carbene intermediate.