Electrophilic Addition

Electrophilic addition

electrons of pi bond are reactive as a Nu: and attracted to electrophilic reagents

Acid Catalyzed Hydration

- converts alkenes to alcohols

- carbocation rearrangements are possible

- reagents: H20, H+, H2SO4 (aq)

Halohydrin

-Reagents: Br2 or Cl2 in H2O

-Bromonium or chloronium ion intercepted by H2O

-Anti addition stereochemical preference

bromination of alkenes (mechanism and stereochemistry?)

alkene with HBr

- alkyl halide on most substituted carbon

- carbocation intermediate

- rearrangements possible

Oxymercuration-Demercuration Conditions

1) Hg(OAc)2, H2O

2) NaBH4

Oxymercuration-Demercuration mechanism

Oxymercuration-Demercuration to make ethers

Oxymercuration-Demercuration of alkynes

Hydroboration-Oxidation conditions

1. BH3, THF

2. H2O2, NaOH

Hydroboration-Oxidation mechanism

Hydroboration-Oxidation of Alkynes

1. BH3, THF / H2O2

2. Hydroboration of terminal alkyne gives an aldehyde.

3. Hydroboration of internal alkyne gives a ketone.

Hydroboration-Oxidation stereochemistry

Markovnikov's Rule

hydrogen will add to the least substituted carbon of the double bond

Anti-Markovnikov Addition

An addition reaction in which a hydrogen atom is installed at the more substituted position and another group (such as a oxygen) is installed at the less substituted position.

Epoxidation of Alkenes

MCPBA, CH2Cl2

stereochemistry of epoxidation

the alkyl substituents stay trans or cis but cyclopropane could add to either face

Simmons-Smith Reaction

A cyclopropanation of an alkene using the carbenoid reagent generated from diiodomethane and the zinc-copper couple.

Simmons-Smith Reaction mechanism

Simmons-Smith Reaction trans alkene (stereochemistry?)

the alkyl substituents stay trans but cyclopropane could add to either face