Kolbe's reaction and Reimer–Tiemann reactionकोल्बे अभिक्रिया और राइमर–टीमन अभिक्रियाKolbe's reaction and Reimer–Tiemann reaction
Class 12 Chemistry · Chapter 7 · interactive diagram
Parts and what they mean
- Phenol + NaOH → sodium phenoxide (फ़ीनॉल + NaOH → सोडियम फ़ीनॉक्साइड) — Phenoxide ion is even more reactive than phenol towards electrophilic substitution.
- (i) CO₂, (ii) H⁺ ((i) CO₂, (ii) H⁺) — CO₂ (weak electrophile) attacks the ring; acidification gives the free acid.
- Main product: ortho-hydroxybenzoic acid (salicylic acid) (मुख्य उत्पाद: ऑर्थो-हाइड्रॉक्सीबेन्ज़ोइक अम्ल (सैलिसिलिक अम्ल)) — –COOH enters ortho to –OH.
- Why Kolbe's reaction works (कोल्बे अभिक्रिया क्यों होती है) — The strongly activated phenoxide ring can react even with a weak electrophile like CO₂.
- Phenol + chloroform + aqueous NaOH (फ़ीनॉल + क्लोरोफ़ॉर्म + जलीय NaOH) — Introduces a –CHO group at the ortho position.
- Intermediate: substituted benzal chloride (–CHCl₂ ortho) (मध्यवर्ती: प्रतिस्थापित बेन्ज़ैल क्लोराइड (ऑर्थो पर –CHCl₂)) — Hydrolysed in the presence of alkali; the –CHCl₂ group becomes –CHO.
- Hydrolysis by NaOH (NaOH द्वारा जल-अपघटन) — –CHCl₂ → –CHO.
- Sodium salt of salicylaldehyde (सैलिसिलैल्डिहाइड का सोडियम लवण) — Still a phenoxide.
- Acidification (H⁺) (अम्लीकरण (H⁺)) — Converts –O⁻Na⁺ back to –OH.
- Product: salicylaldehyde (2-hydroxybenzaldehyde) (उत्पाद: सैलिसिलैल्डिहाइड (2-हाइड्रॉक्सीबेन्ज़ैल्डिहाइड)) — NCERT Intext 7.9 asks you to write this reaction.
Original diagram drawn by Simple Learning Hub, based on the NCERT textbook. Report a mistake