Alkene Reactions

Dehydration

Elimination of alcohols

Dehydration reagents

H2SO4 + heat

Mechanism of dehydration of primary alcohols

1. Make LG 2. E2

Mechanism of dehydration of 2°/3° alcohols

1. Make LG 2. loss of LG 3. Attack β-hydrogen

Hydrohalogenation

Addition of HBr or HCl

Hydrohalogenation reagents

H2O2 + HX

Hydration

Addition of water

Hydration reagents

Water + strong acid

Hydration mechanism

1. Add H from acid 2. Add OH from water 3. Proton transfer to neutralize

Oxymercuration

Addition of water without rearrangements

Oxymercuration reagents

1. Hg(OAc)2, H2O 2. NaBH4

Hydroboration

Anti addition of H2O

Hydroboration reagents

1. BH3 * THF 2. H2O2, H2O, NaOH

Hydrogenation

Addition of H2

Hydrogenation reagents

H2 + metal catalyst

Syn dihydroxylation

Addition of 2 OHs

Syn dihydroxylation reagents

1. KMnO4 + NaOH 2. OsO4 3. NaHSO4

Halogenation

Addition of Cl2 or Br2

Halogenation mechanism

1. Add first X 2. Add second X

Halohydrin

Addition of Cl2 or Br2 in water

Halohydrin reagents

X2 + H2O

Halohydrin mechanism

1. Add X 2. Add H2O 3. Proton transfer

Anti Dihydroxylation

Addition of 2 OHs

Anti Dihydroxylation reagents

1. MCPBA 2. H3O+

Epoxide forming reagent

MCPBA

Anti dihydroxylation mechanism after epoxide forms

1. Protonate epoxide 2. Sn2 3. Proton transfer

Ozonolysis

Oxidative cleavage of C=C

Ozonolysis reagents

1. O3 2. DmS

Oxymercuration mechanism

hydroboration mechanism

dual attack of pi bond with B-H bond leads to cis relationship

Hydrogenation mechanism

Syn dihydroxylation mechanism

Which atom/group adds to the less substituted carbon in HYDROHALOGENATION

Halogen

Which atom/group adds to the less substituted carbon in HYDRATION

H

Which atom/group adds to the less substituted carbon in OXYMERCURATION

H

Which atom/group adds to the less substituted carbon in HYDROBORATION

OH

Which atom/group adds to the less substituted carbon in HALOHYDRIN

Halogen

Is HYDROBORATION syn or anti?

Syn

Is HYDROGENATION syn or anti?

Syn

Is HALOGENATION syn or anti?

Anti

Is HALOHYDRIN syn or anti?

Anti

Is HYDROHALOGENATION stereoselective? (Y/N)

N

Is HYDRATION stereoselective? (Y/N)

N

Is HYDROBORATION stereoselective? (Y/N)

Y

Is HALOGENATION stereoselective? (Y/N)

Y

Is HALOHYDRIN stereoselective? (Y/N)

Y