Markovnikov vs Anti-Markovnikov: Clear Rule Guide & Mechanism
Markovnikov adds the hydrogen to the carbon that already has more hydrogens; Anti-Markovnikov flips the rule and places the hydrogen on the carbon that had fewer.
Students swap them because “anti” sounds like a rebellious exception, so they assume every reverse addition is Anti-Markovnikov, even when reagents like peroxides aren’t present.
Key Differences
Markovnikov: electrophilic addition via carbocation stability; yields more substituted haloalcohol. Anti-Markovnikov: free-radical or hydroboration pathway; yields less-substituted product.
Which One Should You Choose?
Need the more branched alcohol for fragrance synthesis? Go Markovnikov. Making a linear fatty alcohol for biodegradable detergents? Pick Anti-Markovnikov.
Examples and Daily Life
Adding HBr to 1-butene gives 2-bromobutane (Markovnikov). Switch to HBr + peroxide and you get 1-bromobutane—handy for fire-resistant hydraulic fluids.
Does peroxide always trigger Anti-Markovnikov?
Only for HBr. HCl and HI ignore the peroxide effect.
Can hydroboration be called Anti-Markovnikov?
Mechanistically yes, but chemists prefer “hydroboration–oxidation” to stay precise.