251_EA.txt

• 1) addition of hydrogen to less substituted carbon
• 2) addition of X^- ion to carbocation

• More electropositive atom adds first to less substituted carbon.
• Carbocation that forms is maximally stable.

compound containing a halogen ion carrying a positive charge

• inert solvents (CH₂Cl₂, CHCl₃, or CCl₄)
• 1) creation of halonium ion
• 2) attack by nucleophilic halide atom (anti addition)

• H₂; Pd, Pt, or Ni.
• Syn addition.

NaNH₂, liquid NH₃.

• 1. Starting with an alkyne, create sodium alkynide.
• RC|||CH + NaNH₂ --> (liq NH₃) --> RC|||C^-Na⁺ + NH₃
• 2. Combine sodium alkynide with primary halide (S_N2)
• RC|||C^-Na⁺ + R'CH₂Br --> (liq NH₃, 6h) --> RC|||C-CH₂R' + NaBr

Anti-Markovnikov additions (e.g. for hydrogen halides)

Use a peroxide (ROOR).

• Acid catalyzed (e.g. H₃O⁺.
• Markovnikov addition.
• 25 Celsius.
• Reverse of alcohol dehydration.

• Anti hydration of an alkene.
• Markovnikov addition.
• Rearrangements are rare.
• 1) Hg(OAC)₂/THF + H₂O
• water and mercuric acetate add to double bond.
• 2) NaBH₄, OH^-.
• sodium borohydride group replaces acetomercury group with hydrogen.

• Syn hydration of an alkene.
• Anti-Markovnikov addition.
• 1) BH₃/ether or THF.
• H adds to more highly substituted carbon; BH₃ adds to other.
• 2) OH^-/H₂O₂
• OH^- replaces BH₃ group, giving anti-Markovnikov product.

• Anti addition of halogen and hydroxyl group (X and OH).
• Markovnikov addition.
• 1) NBS / 1:1 H₂O:THF

• cyclopentane with carbonyl =O on 2 and 5; N attached to Br at 1.
• Used for halohydrin formation; contributes Br to reaction, few side products.

Hg attached to two carbonyl groups terminating in a methyl. Used during the oxymercuration process.

Hg(O(CO)CH₃)₂

• Turns an alkene into two carbonyls.
• 1) O₃
• 2) Zn, H₂O

• 6-membered ring with O at 1 and N⁺ at 4. O^- and H₃C attached to N⁺.
• stochiometric co-oxidant for catalytic dihydroxylation.

• Reaction A: 1) OsO₄, pyridine. 2) NaHSO₃/H₂O
• Reaction B: alkene + KMnO₄ --> (OH^-, H₂O; cold)
• In osmium tetroxide, cyclic intermediate (carbon bonds to oxygen)and then cleavage at oxygen-metal bonds.

• 1: addition of KMnO₄, OH^-, H₂O, heat
• 2 (if necessary to make carboxylic acid): H₃O⁺