Transcript Alkene Reactions

Alkene Reactions
Addition
Substitution
Diels-Alder
Cleavage
Addition Reactions
 Syn
addition
 Anti addition
 Carbocation formation
 Radical formation
Syn Addition Reactions
Hydrogenation
Hydroxylation
Hydroboration
Anti Addition Reactions
Hydroxylation
Halogenation
Halohydrin
formation
Hydroxylation
 Syn
addition
 Anti addition
C
C
C
C
O O
+
Syn Addition:
C
-
Mn
O
O
O
O
Mn
-
OH
-
H2 O
C
OHOH
+
MnO 2
O
O
permanganate
C
Anti A ddition:
O
R
C
C
C
C
+
O
O
+
H
O
peroxyacid
OH
H2 O
OH
O
R
C
OH
-
OH
Alkene Addition Reactions via Halonium Ions
Halogenation
Halohydrin formation


R
C
C
R
X
X
R
R
C
XX
+
X
C
H2 O
Ha loni um ion
R
R
X
vicinal d ihal id e
wher e X = Cl or B r
OH
R
R
X
hal ohydr in
Carbocation Formation
Hydration
Alcohol
formation
HX Addition
Alkyl
halide formation
Alkene Addition Reactions via Carbocation
Intermediates
Hydration
Hydrogen halide addition
OH
R
R
CH CH2
+
H
+
R CH CH3
secondary
carbocation
(prim ary R+
not form ed)
alcohol
H2 O
X
-
X
CH CH3
R
CH CH3
alkyl halide
where X = Cl, Br, & I
Reaction products are examples of Markovnikov addition
Radical Addition
HBr Addition/ROOR present
Anti-Markovnikov regiochemistry
Peroxide-mediated HBr Addition to Alkenes
R
O + H Br
R
Br
O O R
+
R
CH CH2
2R
R
O
OH + Br
R
CH CH2 Br
secondary radical
(prim ary R
not formed)
R
CH CH2 Br + H Br
R
CH2 CH2 Br + Br
The alkyl bromide product is an example of A nti-Markovnikov addition
Allylic Substitution
NBS/ROOR or NBS/light
O
N
O
Br
N
h
O
+
Br
O
NBS
Br
+
C CH CHx
HBr +
O
+
N
x-1
allyl radical
allylic substrate
HBr
C CH CH
O
Br
N H
O
+ Br2
O
Br
C CH CH
allyl radical
x-1
+ Br2
Br
+
C CH CH
x-1
Diels-Alder Reaction
C
C
C
C
C
C
 Six-membered
ring formation (4+2)
 Diene + Dienophile
Cleavage Reactions of
Alkenes
Ozonolysis
Hot
Potassium Permanganate
Cleavage Reactions of Alkenes
H H
H C C H
H H
R
ozonolysis
C C H
(r eductive workup)
R
R
ozonolysis
(r eductive workup)
2H C H
O
R
O
H
ozonolysis
C C H
(r eductive workup)
ozonolysis
(oxidative workup)
H C C H
or
hot KMnO 4
C H+ H C H
R
O
C R + H C H
O
O
H H
ozonolysis
(oxidative workup)
C C H
or
hot KMnO 4
2 CO2
H H
R
R
R
H
C C H
ozonolysis
(oxidative workup)
or
hot KMnO 4
R
C OH + CO2
O
R
C R + CO2
O