### The Big 5 Named Reactions:
1. **Aldol Condensation:** Aldehydes having α-hydrogen in presence of dilute NaOH form β-hydroxy aldehydes.
2. **Cannizzaro Reaction:** Aldehydes lacking α-hydrogen (Formaldehyde, Benzaldehyde) disproportionate into alcohol and carboxylic acid salt.
3. **Reimer-Tiemann Reaction:** Phenol + Chloroform + aqueous NaOH yields Salicylaldehyde.
4. **Kolbe's Reaction:** Phenol + NaOH + CO2 at 400K and 4-7 atm yields Salicylic acid.
5. **Sandmeyer Reaction:** Diazonium salt + CuCl/HCl yields Chlorobenzene with N2 evolution.
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