Answers Reactions of Alkenes

Additional Problems for practice:
1.) Write a mechanism which accounts for the formation of the observed
product(s) in the following reactions:
a.
+
+
HCl
Cl
Cl
a
Cl-
H+
Cl-
c
a
c
b
hydride
CH3
CH3
H
b H
shift
H
H+
b.
Br
+
HBr
Br-
CH3
CH3
hydride
H
H
H
shift
H
H
2.) Show how you could prepare the following compounds from an alkene:
H3CO
a.
CH2
CH3
1.Hg(OAc)2
CH3
or
CH3OH
2. NaBH4
b.
CH3
OH
c.
1. BH3•THF
CH3
2. H2O2, HO-
1. BH3•THF
OH
2. H2O2, HOCH3
d
CH3CH2C(CH3)2
CH3
HBr
Br
H
CH3
CH3
Br
e.
HBr
H3CH2C
CH3CH2CHCHCH2CH3
CH3
ROOR
heat
H3 C
H
3.) Draw mechanisms for and show the products of the following reactions.
Remember to indicate the regio- and stereochemistry of the products
H
CH3
CH3
H2, Pt
a.
CH3
syn addition of
H2 across the pi bond
CH3
H
CH
CH
3 CH
2 OH
3 CH
2 OH
b.
H
OCH2CH3
H
1. Hg(OAc)2
CH3CH3 CH3 CH2OH
H
d+
AcOHg
H
CH3CH3
Hg
OAc
CH3CH3
2. NaBH4,
HOH
H
OCH2CH3
CH3CH3
H
1. BH3•THF
H
CH3CH3
H
H
H
H
B
H
H3CH3C
CH3CH3
H
B
H
H
B
H
H
H3CH3C
CH3CH3
CH3CH3
2
H
H3CH3C
H
2. H2O2, HO-
H
H
CH3CH3
HO-
O
O
H
CH3CH3
H
B
H
H
O
H
H3CH3C
H
HO
H
racemic
HBr
c.
H
Br
ROOR
heat
H––Br
Br•
H
Br
H
racemic
BrHBr
H
H–––Br
Br
H
H
O
H
H
racemic
H
e.
B
H
H
1. BH3•THF
H
H3 C
2. H2O2, HO-
R
H3 C
S
H
H
racemic
H
H
f.
H3C
B
+ R,S
H
H
H
1. BH3•THF
2. H2O2, HO-
H3 C
H
O H
S
+ R,R
S
racemic
Additional Problems for practice:
1. Show the structures of alkenes that give the following products upon
reaction with warm, concentrated KMnO4
a.
H3CH2C
KMnO4
H
H3CH2C
H
O
H
conc.
H
O
H
H
KMnO4, conc.
H3CH2C
+ CO2
O
HO
b.
H3CH2CH2C
CH3
KMnO4
H3CH2CH2C
CH3
O
H
CH3
conc.
O
H
CH3
KMnO4, conc.
H3CH2CH2C
CH3
+
O
HO
c.
CH3
CH3
CH3
KMnO4
O
CH3
O
+ O
conc.
2.) Show how you could prepare the following compounds from an alkene:
CH3
H
COOH
KMnO4
H
COOH
(a)
conc.
OH
OsO4, H2O2
(b)
H
OH
H
or KMnO4,
cold, dilute
meso
CH3
O
O3
(c)
H
H
O
DMS
CH2I2, Zn/Cu
(d)
or CH2N2, D
OH
(e)
CH3COOOH
CH3
OH
H
H3O+, H2O
CH3
H
racemic
4.) Draw reasonable mechanisms for the following reactions:
H
Br+
Br
Br–––Br
SN2 backside
attack
H
OCH2CH3
+ enantiomer
(a)
HOCH2CH3
H
1. Br2, H2O
(b)
Br
Br+
O
H
2. NaOH, H2O
H
OH2
H
HO-
Br
intamolecular
SN2
O
O-
H
(c)
Br+
Br2, H 2O
Br–––Br
OH
OH
H2O
H
intamolecular
SN2
O
O
Br
Br

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