Markovnikov's Rule: Why Some Alkenes React Faster Than Others If you've ever wondered why HBr adds to an alkene in one specific way and not randomly, this is the rule that explains it — and once you understand why it happens (not just the rule itself), you'll never mix it up again. The Rule Itself When a protic acid (like HBr, HCl, or H₂SO₄) adds across a double bond, the hydrogen ends up on the carbon that already has more hydrogens , and the other group (Br, Cl, etc.) ends up on the more substituted carbon. The old-school phrasing: "the rich get richer" — the carbon with more H's gets even more H's. But Why Does This Happen? This is where most textbooks stop, and where most confusion starts. The real reason is about carbocation stability , not some arbitrary rule to memorize. Here's the mechanism: The acid's H⁺ attacks the double bond first This creates a carbocation on one of the two former double-bond carbons Br⁻ then attacks t...
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