CHEM 2E03 Addition Reactions w/ Alkenes

Hydrohalogenation

• Addition of H-X to an alkene

• Markovnikov addition (Hs add to C with more Hs

• Pi bond attacks H, nucleophilic X attack

Hydrohalogenation w/ peroxide and HBr

• Addition of H-Br to an alkene, facilitated by ROOR

• Anti-Markovnikov addition

Acid-catalyzed hydration

• Forming an alcohol from an alkene using H3O+ (or forming an ether using ROH)

• Markovnikov addition (OH adds to the most substituted C)

• Pi bond attacks H3O+, nucleophilic water attack, deprotonation

Oxymercuration-demercuration

• Forming an alcohol from an alkene using 1. Hg(OAc)2, H2O and 2. NaBH4 (or forming an ether using ROH)

• Markovnikov addition (OH adds to the most substituted C)

• Mercurium prevents carbocation rearrangement

Hydroboration-oxidation

• Addition of H and OH using 1. BH3 + THF and 2. H2O2, NaOH

• Anti-Markovnikov (OH adds to less substituted C)

• Syn addition

Halogenation

• Addition of Cl2/Br2/sometimes I2 across a pi bond

• Anti addition (bromonium ion)

• Enantiomer from the more substituted C is favoured

Hydrogenation

• Addition of H2 across a pi bond using a metal catalyst, turning alkenes into alkanes

• Syn addition

• Catalysts include Pt, Pd, Ni, and Wilkinson’s catalyst

Halohydrin formation

• Addition of a halogen and OH across a pi bond (X2 and H2O)

• Markovnikov addition (OH adds to more substituted C)

• Anti addition (halonium ion)

Anti dihydroxylation

• Addition of 2 OHs across the pi bond in two steps using 1. RCO3H and 2. H3O+, involving an epoxide intermediate

• Anti addition (epoxide)

Syn dihydroxylation

• Addition of 2 OHs across the pi bond in one step using 1. OsO4 and 2. NMO or cold KMnO4

• Syn addition