CHEMISTRY 241A (3-4)
EXAM 3
DOLLINGER
November 8, 2005
Name:__________________
ID#:___________________
GOOD LUCK!
YOU SHOULD HAVE 6 PAGES!!!
BONUS (2 pts):
How many stereoisomers are there of the following compound,
including the one drawn?
21 = 2 stereoisomers
1) (24 points) Draw the principle organic product in each of the
following reactions.
Indicate all stereoisomers formed where appropriate.
B
Br
Br2
Br
A
CH2I2
Zn(Cu)
Br
Br
D
(xs)
KOH
HBr
Br
C
Br
E
Br2
Br
Br
Br
F 1)NaNH2
NH3
2)
Br
G
KMnO4
Br
H
O
O
+
OH
OH
2) (20 points) Compound A has the formula C4H6 and it absorbs2 moles of H2 in
the presence of palladium metal to give B, which has the formula C4H10. Upon
oxidative cleavage with KMNO4, A produces acetic acid. Further, hydrogenation of
A using poisoned palladium catalust (Lindlar) gives compound C, which has the
furmula C4H8. Reduction of A with sodium metal and ammonia gives compound D,
which also has the formula C4H8. Both C and D react with 1 mole of Br2 to give
compounds E and F, respectively. What are compounds A through F? Provide all
stereoisomers formed for each reaction, and circle the appropriate
answer (Chiral or Achiral) for the compound(s) formed for E and F!!!
O
H2
KMnO4
+
Pd-C
H3O
OH
A
B
(C4H6)
H2
Lindlar
Na0/NH3
C
D
Br
(C4H8)
(C4H8)
Br2
Br2
H
Br
H
R
R
H
H
S
Br
H
Br
Br
Br
S
R
H
S
F
E
Chiral / Achiral
Chiral / Achiral
3) (24 points) Provide sequences of reactions to carry out the fooling
transfromatinos from the indicated starting materials. You may use
any reagents as well as ANY organic compounds. More than one step
will be needed. Give the necessary reagents for each individual step.
Give the product of each individual step.
(a)
(12 points)
???
Br2
H2
Pd-C
Br
Br
KOH
1)NaNH2/NH3
2)
Br
(b)
(12 points)
Br
???
KOH
KOH
HBr
Br
4) (16 points)
(a) (12 points) Fill in boves with correct product or starting material.
In each reaction, only one constitutional isomer should be formed.
(i)
1) BH3
2) H2O2/OHO
(ii)
O
1) BH3
HgSO4
2) H2O2/OH-
H2SO4/H2O
O
(iii)
O
HgSO4
H2SO4/H2O
(b) (4 points) the enol below is an intermediate to the ketone formed
in (i). Write the step-wise mechanism for the tautomerization of this
enol to the ketone product under acidic conditions.
H3O+
H
OH
H
O
O
H
OH
O
O
H
H
H
5) (16 points) Determine the relationship of A and B to the structures
that follow. Are the constitutional isomers, identical,
enantiomers, or diastereomers? Indicate your choice in the space
provided.
CHO
r
CHO
OH
H
C
r
CH2OH
C
H
HO
OH
H
s
r
CHO
H
s C
HO
OH
H
H
OH
C s
CH2OH
CH2OH
A
B
ENANT
DIAST.
CONST.
DIAST.
CHO
H
OH
r
s
H
OH
CH2OH
DIAST.
IDENT
OH
H
H
r
r
CHO
OH
CH2OH
IDENT
ENANT
Extra Credit: (1 point) all or nothing!
Circle R or S to describe the configuration of the chirality centers in the
compound below:
CHO
H
OH
H
OH
CH2OH
Front Carbon: R or S
Back Carbon: R or S