Markovnikov's Rule

In-depth explanation of Markovnikov's Rule

Markovnikov's rule describes the regiochemistry of the addition of a hydrogen halide such as HX to an unsymmetrical alkene. The hydrogen adds to the carbon that already carries more hydrogen atoms, and the halogen adds to the more substituted carbon. This outcome follows from the mechanism, because the proton adds to give the more stable carbocation, which is the one with more alkyl groups attached to the positive carbon. The rule is therefore a direct consequence of the relative stabilities of carbocations.

Going deeper: Markovnikov's Rule

Key ideas: In addition of HX to an unsymmetrical alkene, hydrogen goes to the carbon with more hydrogens, so the halide ends on the more substituted carbon; the modern statement is that the more stable carbocation forms. Propene plus HBr gives mainly 2-bromopropane. Rearrangement can override the apparent rule, as in 3-methyl-1-butene plus HCl giving 2-chloro-2-methylbutane.

Common mistakes and connections: Students apply the rule backwards, putting H on the carbon with fewer hydrogens. They also use it for radical reactions with peroxides. It does not matter for symmetrical alkenes like ethene or 2-butene. Links to carbocation stability and hydration.

Visualization of Markovnikov's Rule

Protonation gives the more stable, more substituted carbocation via the lower-energy path, so H adds to the carbon with more hydrogens. The interactive lesson shows this as a live animation or chart.

Worked example and use case

Propene reacts with HBr to give mainly 2-bromopropane, with the bromine on the central carbon.

Where Markovnikov's Rule fits in Organic Chemistry

Markovnikov's Rule is topic 48 of 148 in Organic Chemistry.

Related topics

• Fractional Distillation of Crude OilBeginner
• Octane NumberIntermediate
• Electrophilic AdditionIntermediate
• Anti-Markovnikov AdditionAdvanced
• HydrogenationIntermediate
• Hydration of AlkenesIntermediate

Browse all 148 topics in Organic Chemistry