Acidity of α-hydrogen and aldol condensationα-हाइड्रोजन की अम्लता और ऐल्डोल संघननAcidity of α-hydrogen and aldol condensation

Class 12 Chemistry · Chapter 8 · interactive diagram

Parts and what they mean

• Ethanal: α-H shown in front (एथेनैल: α-H आगे दिखाया) — The H on the carbon next to C=O is acidic.
• Enolate (carbanion form) (इनोलेट (कार्बऋणायन रूप)) — Negative charge on the α-carbon…
• Enolate (oxygen form) (इनोलेट (ऑक्सीजन रूप)) — …delocalised onto the electronegative oxygen. This resonance stabilisation + the electron-withdrawing C=O make α-H acidic.
• Two molecules of ethanal (एथेनैल के दो अणु) — Both have α-hydrogens: one acts as the nucleophile (via its enolate), the other as the electrophile.
• 3-Hydroxybutanal (aldol) (3-हाइड्रॉक्सीब्यूटेनैल (ऐल्डोल)) — A β-hydroxy aldehyde: ALDehyde + alcohOL = aldol.
• But-2-enal (aldol condensation product) (ब्यूट-2-ईनैल (ऐल्डोल संघनन उत्पाद)) — An α,β-unsaturated aldehyde, formed by loss of water on heating.
• Two molecules of propanone (प्रोपेनोन के दो अणु) — Ketones with α-H also undergo aldol reaction (Ba(OH)₂ as base).
• 4-Hydroxy-4-methylpentan-2-one (ketol) (4-हाइड्रॉक्सी-4-मेथिलपेन्टेन-2-ओन (कीटॉल)) — A β-hydroxy ketone.
• 4-Methylpent-3-en-2-one (mesityl oxide) (4-मेथिलपेन्ट-3-ईन-2-ओन (मेसिटिल ऑक्साइड)) — The α,β-unsaturated ketone — the name aldol condensation still applies to ketones.
• But-2-enal — from two ethanal molecules (ब्यूट-2-ईनैल — दो एथेनैल अणुओं से) — Simple (self) aldol product.
• 2-Methylpent-2-enal — from two propanal molecules (2-मेथिलपेन्ट-2-ईनैल — दो प्रोपेनैल अणुओं से) — Simple (self) aldol product.
• Pent-2-enal — ethanal (nucleophile) + propanal (electrophile) (पेन्ट-2-ईनैल — एथेनैल (नाभिकस्नेही) + प्रोपेनैल (इलेक्ट्रॉनस्नेही)) — Cross aldol product.
• 2-Methylbut-2-enal — propanal (nucleophile) + ethanal (electrophile) (2-मेथिलब्यूट-2-ईनैल — प्रोपेनैल (नाभिकस्नेही) + एथेनैल (इलेक्ट्रॉनस्नेही)) — Cross aldol product.
• Benzaldehyde (no α-H, so only an electrophile) (बेंज़ैल्डिहाइड (α-H नहीं, केवल इलेक्ट्रॉनस्नेही)) — Its carbonyl is attacked by the enolate of acetophenone.
• Acetophenone (has α-H, gives the enolate) (ऐसीटोफ़ीनोन (α-H है, इनोलेट देता है)) — A ketone used as one component of a cross aldol.
• 1,3-Diphenylprop-2-en-1-one (benzalacetophenone), major product (1,3-डाइफ़ेनिलप्रोप-2-ईन-1-ओन (बेन्ज़ैलऐसीटोफ़ीनोन), मुख्य उत्पाद) — Cross aldol between a ketone and an aldehyde without α-H.

Original diagram drawn by Simple Learning Hub, based on the NCERT textbook. Report a mistake