Alkene Addition Reactions

This flashcard set covers key reactions, mechanisms, regiochemistry, and stereochemistry of alkene addition reactions.

Hydrohalogenation Reaction

Alkene + H-X (where X is Cl, Br, or I) → Alkyl halide

Hydrohalogenation Mechanism

Protonation → carbocation intermediate → nucleophilic attack by X⁻

Hydrohalogenation Regiochemistry

Markovnikov (X goes to more substituted carbon)

Hydrohalogenation Stereochemistry

Not stereospecific

Hydrohalogenation (Br and peroxide present) Reaction

Alkene + HBr + ROOR → Alkyl bromide

Hydrohalogenation (Br and peroxide present) Mechanism

Radical chain mechanism (initiation, propagation, termination)

Hydrohalogenation (Br and peroxide present) Regiochemistry

Anti-Markovnikov (Br to less substituted carbon)

Hydrohalogenation (Br and peroxide present) Stereochemistry

Not stereospecific

Acid-Catalyzed Hydration Reaction

Alkene + H₂O (H⁺) → Alcohol

Acid-Catalyzed Hydration Mechanism

Hydration reaction: Carbocation intermediate → nucleophilic attack from H₂O → deprotonation

Acid-Catalyzed Hydration Regiochemistry

Markovnikov (X goes to more substituted carbon)

Acid-Catalyzed Hydration Stereochemistry

Not stereospecific

Oxymercuration–Demercuration Reaction

1. Alkene + Hg(OAc)₂, H₂O

2. NaBH₄ → Alcohol

Oxymercuration–Demercuration Mechanism

Hydration reaction without carbocation intermediate (mercurinium ion)

Oxymercuration–Demercuration Regiochemistry

Markovnikov (X goes to more substituted carbon)

Oxymercuration–Demercuration Stereochemistry

Anti addition (two substituents added to opposite sides/faces of double/triple bond)

Hydroboration–Oxidation Reaction

1. Alkene + BH₃•THF

2. H₂O₂, OH⁻ → Alcohol

Hydroboration–Oxidation Mechanism

Concerted (no intermediate carbocation)

Hydroboration–Oxidation Regiochemistry

Anti-Markovnikov (X to less substituted carbon)

Hydroboration–Oxidation Stereochemistry

Syn addition (two substituents added to same sides/faces of double/triple bond)

Catalytic Hydrogenation Reaction

Alkene + H₂ and heterogenous catalyst (Pd, Pt, or Ni) → Alkane — reduction reaction

Catalytic Hydrogenation Mechanism

Surface reaction on metal catalyst

Catalytic Hydrogenation Regiochemistry

Not applicable

Catalytic Hydrogenation Stereochemistry

Syn addition (two substituents added to same sides/faces of double/triple bond)

Halogenation Reaction

Alkene + X₂ (where X is Cl or Br)₂ → Vicinal dihalide

Halogenation Mechanism

Halonium ion intermediate

Halogenation Regiochemistry

Not applicable

Halogenation Stereochemistry

Anti addition (two substituents added to opposite sides/faces of double/triple bond)

Halohydrin Formation Reaction

Alkene + X₂ (where X is Cl or Br)₂ + H₂O → Halohydrin

Halohydrin Formation Mechanism

Halonium ion → water attack

Halohydrin Formation Regiochemistry

OH to more substituted carbon (Markovnikov-like)

Halohydrin Formation Stereochemistry

Anti addition (two substituents added to opposite sides/faces of double/triple bond)

Anti Dihydroxylation Reaction

Alkene → epoxide (peracid) → acid-catalyzed opening → trans diol

Anti Dihydroxylation Mechanism

Epoxide intermediate → backside attack

Anti Dihydroxylation Regiochemistry

Attack at more substituted carbon (acidic conditions)

Anti Dihydroxylation Stereochemistry

Anti addition

Syn Dihydroxylation Reaction

Alkene + OsO₄ (or cold KMnO₄) → cis diol

Syn Dihydroxylation Mechanism

Cyclic intermediate

Syn Dihydroxylation Regiochemistry

Not applicable

Syn Dihydroxylation Stereochemistry

Syn addition

Oxidative Cleavage Reaction

Alkene + O₃ → carbonyls (aldehydes/ketones) (or KMnO₄ → ketones/carboxylic acids)

Oxidative Cleavage Mechanism

Ozonide intermediate → cleavage

Oxidative Cleavage Regiochemistry

Double bond is broken

Oxidative Cleavage Stereochemistry

Not applicable