Named reactions of phenol constitute a consistent NEET topic. All three major reactions exploit the activated nature of the phenol ring.

1. Kolbe Reaction (Kolbe-Schmitt Carboxylation):

$\text{C}_6\text{H}_5\text{O}^-\text{Na}^+ + \text{CO}_2 \xrightarrow{125°C,\ 4\text{-}7\ \text{atm}} [\text{sodium salicylate}] \xrightarrow{\text{H}_3\text{O}^+} \text{Salicylic acid}$

• Substrate: sodium phenoxide (NOT phenol directly)
• Reagent: $CO_{2}$ under pressure
• Conditions: 125°C, 4-7 atm
• Product: salicylic acid (SMILES:OC(=O)c1ccccc1O) — -COOH at ortho position
• Significance: salicylic acid → acetylation → aspirin (acetylsalicylic acid)

2. Reimer-Tiemann Reaction (Formylation):

$\text{C}_6\text{H}_5\text{OH} + \text{CHCl}_3 \xrightarrow{\text{NaOH, reflux}} \text{C}_6\text{H}_4(\text{OH})(\text{CHO}) + 3\text{NaCl} + \text{H}_2\text{O}$

• Substrate: phenol
• Reagent: $CHCl_{3}$ + NaOH
• Intermediate: dichlorocarbene (:$CCl_{2}$) — electrophilic, attacks phenoxide at ortho position
• Product: salicylaldehyde (SMILES:O=Cc1ccccc1O) — ortho-hydroxybenzaldehyde

3. Bromination of Phenol:

$\text{C}_6\text{H}_5\text{OH} + 3\text{Br}_2/\text{H}_2\text{O} \rightarrow 2,4,6\text{-tribromophenol} + 3\text{HBr}$

• No Lewis acid catalyst ($FeBr_{3}$) required — unlike benzene
• Product: white crystalline precipitate
• Also serves as qualitative test for phenol

Summary Comparison: