Octet

Octet / Reactions

Hydrohalogenation (HX Addition)

Hydrohalogenation (HX Addition) (Electrophilic Addition Addition.) Converts CC=C to CC(C)Br using HBr (or HCl, HI).

Addition

Reaction details

Name

Hydrohalogenation (HX Addition)

Type

Addition

Subtype

Electrophilic Addition

Starting Material

CC=C

Product

CC(C)Br

Reagents
  • HBr (or HCl, HI)

Mechanism
  1. Smiles

    CC=C

    Description

    Propene: π electrons are nucleophilic

  2. Smiles

    CC=C

    Description

    H⁺ adds to less substituted carbon (forms more stable carbocation)

  3. Smiles

    C[CH+]C

    Description

    Secondary carbocation intermediate

  4. Smiles

    CC(C)Br

    Description

    Halide attacks carbocation (shown: Br⁻)

Regiochemistry

Markovnikov: H adds to carbon with more H's, X to more substituted carbon

Tips
  1. Carbocation stability determines regiochemistry

  2. Rearrangements possible with carbocation intermediate

  3. Follows Markovnikov's rule

  4. Mechanism shown for HBr; HCl and HI work analogously

Related Reactions
  • hydroboration

  • halohydrin-formation

This is one row of the Reaction roadmap sheet - print all 83 reactions on one page.