Phenolic group can be identified by a positive:

Step 1: Understand each test

• Phthalein dye test: Phenol reacts with phthalic anhydride in presence of conc. $\ce{H2SO4}$ to give a pink/red fluorescent dye (phenolphthalein or fluorescein). This test is specific for phenols (the hydroxyl group on the benzene ring). ✓

• Lucas test: Distinguishes between primary, secondary, and tertiary alcohols (not phenols). Uses $\ce{ZnCl2 + conc. HCl}$. Phenols do NOT react with Lucas reagent.

• Tollen's test: Detects aldehydes (not phenols). Silver mirror formed from $\ce{Ag(NH3)2^+}$.

• Carbylamine test: Identifies primary amines (not phenols).

Step 2: Confirm phthalein dye test for phenol

The reaction: Phenol + phthalic anhydride $\xrightarrow{\text{conc. }\ce{H2SO4}}$ phenolphthalein (colourless in acid, pink in base) or fluorescein. Both are phthalein dyes formed specifically from phenols.

Answer: Phthalein dye test

Key Points to Remember:

• Phthalein dye test: specific for phenol (aromatic -OH).
• Lucas test: alcohols (not phenols).
• Tollen's/Fehling's test: aldehydes.
• Carbylamine test: primary amines.
• Also, FeCl3 gives violet/purple colour with phenols — another test for phenolic group.