-
Hydrohalogenation [alkene]
HX
---->
- Addition of H and X across 2x bond
- Markovnikov
- Racemic Mixture
- Rearrangement possible
- MECHANISM: Proton transfer from HBr to 2x bond. Nucleophilic attack by HBr on newly-formed carbocation.
-
Hydrohalogenation [alkene]
HBr
---->
ROOR
- Addition of H and Br across 2x bond
- Anti-markovnikov
- Racemic Mixture
- No rearrangement
- MECHANISM: Radical mechanism
-
Acid-catalyzed hydration [alkene]
H3O+
----->
- Addition of H and OH across 2x bond
- Markovnikov
- Racemic mixture
- Rearrangement possible
- Reversable - excess acid favors alkene, excess H2O favors alcohol
- MECHANISM: 2x bond grabs H from H3O+, creates carbocation, rearranges, H2O attacks, H2O attacks the newest C+ leaving OH
-
Oxymercuration-demercuration [alkene]
1) Hg(OAc)2, H2O
----------------->
2) NaBH4
- Addition of H and OH across 2x bond
- Markovnikov
- Racemic mixture
- No rearrangement
- MECHANISM: Mercurium ion intermediate
-
Hydroboration-oxidation [alkene]
1) BH3*THF
------------->
2) HOOH, NaOH
- Addition of H and OH across 2x bond
- Anti-markovnikov
- Syn addition (but only trans product)
- MECHANISM: H on BH3 is replaced with the less-substituted end of alkene, H goes to other end. Repeated for all three H's until BR3 is seen. Creates three sets of ROH.
-
Catalytic Hydrogenation [alkene]
H2
---->
Pt
- Alkene to alkane
- Syn addition
- NOTE - Wilkinson's catalyst is a soluble catalyst that will work in the same manor
-
Bromination (Halogenation) [alkene]
Br2
----->
- Addition of Br2 across 2x bond
- Anti-addition
- MECHANISM: Formation of bromonium ion
- NOTE - solvent must be inert (no water!)
- NOTE - also viable for Cl2
-
Halohydrin Formation [alkene]
Br2
---->
H2O
- Addition of Br and OH across 2x bond
- Markovnikov
- Anti addition
- MECHANISM: H2O makes second attack, because it is more prevalent than Br-
-
Dihydroxylation [alkene]
1) RCO3H
----------->
2) H3O+
- Addition of OH and OH across 2x bond
- Anti-addition
- MECHANISM: alkene -> epoxide using peracid. Acid or base catalyzed ring opening. (same results, diff mech).
- NOTE - step 1 could also be MCPBA
- NOTE - step 2 could also be base
-
Dihydroxylation [alkene]
1) OsO4
--------->
2) Na2SO4/H2O
- Addition of OH and OH across 2x bond
- Syn addition
- MECHANISM: Osmate ester intermediate
- NOTE - Step 2 can be replaced with NMO for cost purposes
- NOTE - reaction can be done with KMnO4 / NaOH at cold temp, for much less $$ and less toxicity BUT yield will suffer
-
Ozonolysis [alkene]
1) O3
------->
2) DMS
- Cleavage across the 2x bond, creating ketone or aldehyde
- MECHANISM: Molozonide intermediate -> ozonide intermediate
- NOTE - when using KMnO4 + heat similar rxn occurs, but aldehydes are oxidized to acids.
- NOTE - Step 2 could be (CH3)2S
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