Reactions of Alkenes: Summary
Intermediate:
Carbocation
Regiochemisty:
Markovnikov* Anti-Markovnikov*
Addition:
Rearrangements?
Radical
3-Membered Ring None or Cyclic (concerted)
Markovnikov-like
N/A
Syn & Anti
Syn & Anti
Anti
Syn
yes
no
no
no
*the reaction goes through the pathway of the most stable intermediate;
the more substituents on an electron deficient carbon (carbocation or radical), the greater its stability
Stereochemistry:
• If the reactants are optically inactive (achiral), the products will be optically inactive (achiral, racemic or meso)
• If the reactants are optically active (chiral), the products will be optically active (unequal mixture of
enantiomers, unequal mixture of diastereomers, or 1 enantiomer)
• Use 2n of the product to predict the maximum number of stereoisomers
(if just anti or just syn addition, divide the maximum number of stereoisomers by 2)
Predicting the type of intermediate:
• Carbocation - H is the electrophile (no lone pair to share with the empty p orbital)
• Radical - an initiator with a weak bond (ex. ROOR) and an energy source (heat or light) is present
• 3-Membered Ring - the electrophile has a lone pair of electrons available to share with the empty p orbital
• None or Cyclic - the electrophile can both accept and donate electrons at the same time
HX
(X = Br, Cl, I)
CH3
heat or light
(NOT HCl or HI)
Br
(X = Br, Cl)
(X = Br, Cl)
CH3
X
X
CH3
OH
X
H3O+, H2O
OH
CH3
Alkyl halide
Radical
syn + anti
Anti-Markovnikov
Vicinal dihalide
3-membered
ring
anti
Markovnikov-like
Halohydrin
3-membered
ring
anti
Markovnikov-like
Alcohol
Carbocation
syn + anti
Markovnikov
Alcohol
3-membered
ring
anti
Markovnikov-like
Alcohol
None
(concerted)
syn
Anti-Markovnikov
H3C
1. Hg(OAc)2, H2O
2. NaBH4
OH
H3C
1. BH3, THF
CH3
Markovnikov
CH3
X2, H2O
CH3
syn + anti
CH3
X2
CH3
Carbocation
H3C
HBr, ROOR
CH3
Alkyl halide
X
2. HOOH, NaOH
HO
CH3
CH3
1. Hg(OAc )2, MeOH
2. NaBH4
H3 C
CHX3, KOH
CH3
X
C
OCH3
Ether
3-membered
ring
anti
CH3
Cyclopropane
None
(concerted)
syn
N/A
Cyclopropane
None
(concerted)
syn
N/A
Alkane
Heterogeneous
syn
N/A
Epoxide
None
(concerted)
syn
N/A
trans-1,2-diol
3-membered
ring
anti
N/A
trans-1,2-diol
None
(concerted)
anti
N/A
X
CH2I2, Zn(Cu)
CH3
H
C
CH3
H
H2, Pd/C
CH3
(or H2, PtO2)
CH3
RCO3H
CH3
O
CH3
H3O+, H2O
O
CH3
HO
OH
CH3
-
OH, H2O
O
CH3
Markovnikov-like
HO
CH3
OH
Cyclic
(concerted)
syn
Cyclic
(concerted)
syn
Cyclic
(concerted)
syn
Aldehydes
and Ketones
Cyclic
(concerted)
syn
CH3
Carboxylic acids
and Ketones
Cyclic
(concerted)
syn
CH3
Carboxylic acids and
Ketones
Cyclic
(concerted)
syn
1. OsO4
CH3
2. NaHSO3, H2O
(or H2O 2)
HO
CH3
OH
HO
CH3
OH
KMnO4 (cold, dilute)
-
OH, H2O
CH3
HO
CH3
OH
HIO4, H2O
H
CH3
cis-1,2-diol
cis-1,2-diol
Aldehydes
and Ketones
O O
1. O3
CH3
+
2. Zn(H3O ) or (CH3)2S
1. O3
CH3
H3O+, H2O
CH3
O O
HO
2. H2O2
KMnO4 (hot, conc'd)
CH3
H
O O
HO
O O