Chemistry 233
Organic I
March 13, 2010
George A. O’Doherty
Exam #2 (AK)
Name:
ID#
(Please also put your name and ID# on the last page)
There is a total of 200 points for this exam.
[I] (25 points/2 points each)
Rank the following bonds in terms of relative bond strength by writing the letter (a, b or c) in the appropriate
box.
Strongest
Ha
Weakest
Hc
C
B
A
Hb
A)
Strongest
Weakest
Clb
C
Cla
A
B
Clc
B)
Strongest
Ha
Weakest
Hb
A
B
C
Hc
C)
Strongest
Ha
Hc
A
Hb
D)
Weakest
B
C
[II] (30 points/2 points each)
Please indicate whether the molecule is chiral or achiral by circling the appropriate term.
A=
OH
HO
OH
OH
B=
OH
C=
OH
Chiral
Achiral
D=
Chiral
Achiral
E=
Chiral
Achiral
Achiral
Chiral
F=
Chiral
Achiral
Chiral
Achiral
OH
G=
H=
Chiral
Achiral
I=
Chiral
Achiral
Chiral
Achiral
Cl
CH3
OH
OH
OH
J=
K=
L=
Cl
Chiral
Achiral
Chiral
Achiral
Chiral
Achiral
OH
M=
N=
Chiral
Achiral
O=
Chiral
Achiral
Chiral
Achiral
[III] (30 points)
Please 1) draw the product from the following reactions (2 points each)
and 2) answer the related questions (1 point each).
a)
The ratio of B to H2O is 1:1.
LiOH
+
(S)
+ H2O
(R) OH
Br
A
B
chiral
achiral
SN1, SN2, E1 or E2
SN1, SN2, E1 or E2
i) Is A chiral or achiral (if so, indicate in the small box)?
ii) Is B chiral or achiral (if so, indicate in the small box)?
iii) Label all stereocenters in the products with an R or S.
iv) Is the reaction that produced A SN1, SN2, E1 or E2? (circle the appropriate term)
v) Is the reaction that produced B SN1, SN2, E1 or E2? (circle the appropriate term)
b)
Products C and D are isomer.
H
(R)
Br
H
LiCN
H
CN
CN
+
(R)
(R)
C
(R)
(R)
chiral
(S)
D
SN1, SN2, E1 or E2
chiral
SN1, SN2, E1 or E2
i) Is A chiral or achiral (if so, indicate in the small box)?
ii) Is B chiral or achiral (if so, indicate in the small box)?
iii) Label all stereocenters in the products with an R or S.
iv) Is the reaction that produced C SN1, SN2, E1 or E2? (circle the appropriate term)
v) Is the reaction that produced D SN1, SN2, E1 or E2? (circle the appropriate term)
vi) What is the stereochemical relationship between products C and D (3 points)?
C and D are Diastereomers
c)
The ratio of E to H2O is 1:1.
(R)
Br
(R)
Br
LiOH
+
+ H2O
D
H D
(S)
E
H D
(S)
achiral
SN1, SN2, E1 or E2
F
chiral
SN1, SN2, E1 or E2
i) Is E chiral or achiral (if so, indicate in the small box)?
ii) Is F chiral or achiral (if so, indicate in the small box)?
iii) Label all stereocenters in the products with an R or S.
iv) Is the reaction that produced E SN1, SN2, E1 or E2? (circle the appropriate term)
v) Is the reaction that produced F SN1, SN2, E1 or E2? (circle the appropriate term)
[IV] (40 points)
Please provide reagents for the following conversions. Some transformation may require more than one step.
a) (8 points)
How?
Br2
h!/AIBN
Br
KOt-Bu
b) (8 points)
CN
HOW?
(+/–)
HBr
or
HBr
h!/AIBN
Br
KCN
(+/–)
c) (8 points)
How?
CN
Br2
h!/AIBN
Br
KCN
d) (16 points)
How?
How?
CN
KOt-Bu
Br2
h!/AIBN
Br
Br2
h!/AIBN
Br
KCN
[V]
(25 points/5 points each)
For the following five sets of reactions, indicate (by circling the letter) the faster/fastest reaction.
If a number of the reaction rates are the same, then circle both reactions? (5 points each)
a)
A
Br
KOt-Bu
H
KOt-Bu
H
B
Br
b)
S
Na
SCH3
A
B
O
Na
+
MeI
+
MeI
OCH3
c)
A
Br
+
KOt-Bu
i-Pr
(+/–)
B
Br
+
KOt-Bu
i-Pr
(+/–)
d)
A
+
NBS
h!
AIBN
NBS
h!
AIBN
Br
Br
B
+
(+/–)
Br
C
+
NBS
h!
AIBN
(+/–)
e)
Br
A
+
Br2
h!
AIBN
B
+
Br2
h!
AIBN
C
+
Br2
h!
AIBN
Br
Br
D
+
Br2
h!
AIBN
Br
[VI]
(50 points/5 points each)
In the boxes provided on the next page draw the products (A-J) for the reactions drawn below. Please
indicate relative stereochemistry when appropriate. If the product is formed as part of a racemic mixture only
draw one enantiomer. Also, if the product is formed as part of a racemic mixture this will be indicated by a
(+/–) next to the letter. (Hint: some products are formed more than once)
C4H9Br
H2
Pd/C
+
A
C7H16
B
C6H12
C6H12 C
Br
C5H12
HBr
D
C4H8
A
LiCuEt2
LiCuMe2
Br
E
HBr
C6H14
KOt-Bu
Br
C4H9Br
F
LiCuMe2
+
LiCN
G
CN
C5H9N
H
KOt-Bu
HBr, h!
1% AIBN
CuLi
KOt-Bu
2
G
C6H12
B
Br
E
C4H9Br
H2
Pd/C
H2
Pd/C
H
H2
Pd/C
D
C6H14
LiCN
HBr
Br
Li
H
J
C6H10
C4H9Br
NBS, h!
1% AIBN
I
LiCuMe2
CN
C5H9N
A=
B=
C7H16
C=
C6H12
D=
C6H14
C6H12
E=
F=
Br
(+/–)
C4H9Br
C5H12
G=
Br
H=
C5H9N
C4H9Br
I=
CN
J=
H
CN
(+/–)
C5H9N
C6H10