Orgo I Organic Reaction Mechanisms

Hydration i (Acid-Catalyzed Hydration)

• Typical Reagents: H₂O, H₂SO₄

• Where −OH Ends Up: More sub. carbon

• Regiochemical Rule: Markovnikov

Hydration ii (Oxymercuration-Demercuration) Reaction

• Typical Reagents:

  • Hg(OAc)₂, H₂O

  • NaBH₄

• Where −OH Ends Up: More sub. carbon (no rearrangement)

• Regiochemical Rule: Markovnikov

Hydration iii (Hydroboration-Oxidation)

• Adding H and OH

• Typical Reagents:

  • BH₃ ^. THF

  • H₂SO₄, NaOH

• Where −OH Ends Up: less substituted carbon

• Regiochemical Rule: Anti-Markovnikov

Hydrohalogenation i Markovnikov

• Adding H and Halogen

• Typical Reagents:

  • HCl, HBr, HI alone

  • H₂SO₄, NaOH

• Where X Ends Up: more substituted carbon

• Regiochemical Rule: Markovnikov

Hydrohalogenation ii Anti-Markovnikov

• Adding H and X

• Typical Reagents:

  • HBr with peroxides (ROOR or H₂O₂)

  • H₂SO₄, NaOH

• Where −OH Ends Up: less substituted carbon via free-radical mechanism

• Regiochemical Rule: Anti-Markovnikov

Halohydrin

• Adds: Halogen (X) or acohol (OH, ROH)

• Typical Reagents:

  • Br₂ or Cl₂ in H₂O or an alcohol ROH

• Where −OH Ends Up: more substituted carbon

• Regiochemical Rule: Anti-Markovnikov

• Stereochem.: Anti-addition (X and OH will be trans to each other)

Syn Dihydrolyxation

• Addition of two OH groups

• Syn dihydrolyxation

  • Reagents: catalytic OsO₄ with NMO (or cold, dilute KMnO₄, NaOH)

  • Stereochem: Syn addition, OH on same face via a (cyclic osmate ester)

Anti Hydrolyxation

• Reagents:

  • mCBPA (alkene with a peroxyacid/peracid to form an epoxide — epoxidation)

  • H₃O⁺

• Stereochem: Anti-Additon Acid opens epoxide via backside attack, delivering two OH groups on opposite faces

Hydrogenation

• Reagents: H₂ with a metal catalyst (Pd/C,Pt, or Ni)

• What adds: Two hydrogen atoms

• Stereochemistry: Syn Addition Both H2 are delivered simultanoeously from the catalyst surface to one face of the alkene

Oxydative Cleavage (Ozonolysis)

• Reagents:

  • O₃

  • DMS (or Zn/H₂O) for reductive

• Mechanism: Completely slices the $\text{C=C}$ double bond in half, capping both ends with carbonyl oxygens C- - C. Yields aldehydes and ketones. (Using oxidative workup like C - - O converts aldehydes into carboxylic acids).