Acid-catalysed hydration of an alkene: mechanismऐल्कीन का अम्ल-उत्प्रेरित जलयोजन: क्रियाविधिAcid-catalysed hydration of an alkene: mechanism
Class 12 Chemistry · Chapter 7 · interactive diagram
Parts and what they mean
- Ethene (the alkene, C=C π bond) (एथीन (ऐल्कीन, C=C π बंध)) — The π electrons of C=C attack H⁺ — the alkene acts as a nucleophile.
- Hydronium ion H₃O⁺ (the electrophile) (हाइड्रोनियम आयन H₃O⁺ (इलेक्ट्रॉनस्नेही)) — Formed from H₂O + H⁺; it gives a proton to the alkene.
- Curved arrows, step 1 (वक्र तीर, पद 1) — Arrow 1: π bond electrons → H. Arrow 2: the H–O bond electrons move onto O, so H₂O leaves.
- Carbocation CH₃–CH₂⁺ (कार्बधनायन CH₃–CH₂⁺) — Positively charged carbon with only six electrons; it is attacked by water.
- Water as nucleophile (lone pair on O) (नाभिकस्नेही के रूप में जल (O पर एकाकी युग्म)) — A lone pair of O forms the new C–O bond.
- Curved arrow, step 2: lone pair of O → C⁺ (वक्र तीर, पद 2: O का एकाकी युग्म → C⁺) — Arrow starts at the electron pair and ends at the atom that receives it.
- Protonated alcohol (alkyloxonium ion) (प्रोटॉनित ऐल्कोहॉल (ऐल्किलऑक्सोनियम आयन)) — O now has three bonds and a positive charge.
- Curved arrows, step 3 (deprotonation) (वक्र तीर, पद 3 (विप्रोटॉनन)) — A water molecule takes H⁺; the O–H bond pair returns to O, giving the neutral alcohol.
- Product: ethanol (उत्पाद: एथेनॉल) — H₃O⁺ is regenerated, so H⁺ is a catalyst.
- Markovnikov's rule for unsymmetrical alkenes (असममित ऐल्कीनों के लिए मार्कोनीकॉफ़ नियम) — Propene gives propan-2-ol: H goes to the CH₂ end, –OH to the middle carbon (the more stable 2° carbocation forms).
Original diagram drawn by Simple Learning Hub, based on the NCERT textbook. Report a mistake