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H-X addition steps
- 1) addition of hydrogen to less substituted carbon
- 2) addition of X- ion to carbocation
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Markovnikov's rule
- More electropositive atom adds first to less substituted carbon.
- Carbocation that forms is maximally stable.
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Halonium ion
compound containing a halogen ion carrying a positive charge
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X2 addition: solvents? steps?
- inert solvents (CH2Cl2, CHCl3, or CCl4)
- 1) creation of halonium ion
- 2) attack by nucleophilic halide atom (anti addition)
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Catalytic hydrogenation: reagents? syn/anti?
- H2; Pd, Pt, or Ni.
- Syn addition.
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Creation of sodium alkynides: reagents? solvent?
NaNH2, liquid NH3.
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Synthesizing longer alkynes: steps?
- 1. Starting with an alkyne, create sodium alkynide.
- RC|||CH + NaNH2 --> (liq NH3) --> RC|||C-Na+ + NH3
- 2. Combine sodium alkynide with primary halide (SN2)
- RC|||C-Na+ + R'CH2Br --> (liq NH3, 6h) --> RC|||C-CH2R' + NaBr
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Effect of peroxides (ROOR):
Anti-Markovnikov additions (e.g. for hydrogen halides)
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How to produce anti-Markovnikov additions?
Use a peroxide (ROOR).
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Hydration of alkenes: catalyst? regiochem? temperature? mechanism?
- Acid catalyzed (e.g. H3O+.
- Markovnikov addition.
- 25 Celsius.
- Reverse of alcohol dehydration.
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Oxymercuration/demercuration: purpose? regiochem? rearrangements? mechanism?
- 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.
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Hydroboration/oxidation: purpose? regiochem? mechanism?
- 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.
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Halohydrin formation: purpose? regiochem? mechanism?
- Anti addition of halogen and hydroxyl group (X and OH).
- Markovnikov addition.
- 1) NBS / 1:1 H2O:THF
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NBS: structure? purpose?
- 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.
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Mercury oxoacetate (HgOAc) : structure? purpose?
Hg attached to two carbonyl groups terminating in a methyl. Used during the oxymercuration process.
Hg(O(CO)CH3)2
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Ozonolysis: purpose? reagents?
- Turns an alkene into two carbonyls.
- 1) O3
- 2) Zn, H2O
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NMO: structure? purpose?
- 6-membered ring with O at 1 and N+ at 4. O- and H3C attached to N+.
- stochiometric co-oxidant for catalytic dihydroxylation.
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Syn 1,2 dihydroxylation: reagents (2 reactions)? Mechanism?
- 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.
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Cleavage with Hot Basic KMnO<sub>4</sub>
- 1: addition of KMnO<sub>4</sub>, OH<sup>-</sup>, H<sub>2</sub>O, heat
- 2 (if necessary to make carboxylic acid): H<sub>3</sub>O<sup>+</sup>
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