Download Exam 3 w/ Answers (2002)

CHEMISTRY 61
Exam 3
Dr. M.T. Crimmins
November 14, 2002
Name___________________________________________
Pledge: I have neither given nor received aid on this exam.
Signature________________________________________
I.
Reactions: Predict the major organic product of the following reactions. If more than one product is
formed give both and indicate the major product. Indicate stereochemistry where necessary. (4
points each)
1.
H 3C
H
H 3C
K + –OC(CH3)3
H
CH2CH3
CH2CH3
Br
H
2.
H 3C
CH3OH
Br
H 3C
OCH3
25°C
3.
HO
CH3
CH3
H3PO4
CH3
heat
CH3
4.
HI (excess)
CH3
H 3C C CH3
OCH3
CH3
H 3C C CH3
I
+
ICH3
5.
O
C CH2 CH3
H2O, H2SO4
C C CH3
HgSO4
6.
CH3
OCH3
CH3
CH3OH, H+
O
OH
7.
OH
OCH3
NaH, CH3I
–1–
8.
1. n-BuLi
H C C H
2. H 2C CH2
O
H C C CH2CH2OH
9.
CN
Na+ – CN
I
H 3C
H 3C
10.
OH
CH2
C
H 3C
CH3
CH3
O C CH3
CH3
H2SO4
11.
H
1. Br2, H2O
O
2. NaH
H
12.
Br
H 3C C C CH3
Br
Br2
H 3C C C CH3
13. Indicate whether the following reactions are more likely to proceed by an E1, E2, SN1 or SN2
mechansim. (2 points each)
CH2CH3
a.
H 3C C Br
CH3CH2S
–
S N2
H
Br
b.
E2
CH3O – + Na
C CH3
CH3
OH
c.
C H
CH3
OCH3
d.
II.
E1
H3PO4
heat
S N1
HI
C CH3
25 °C
CH3
Multiple Choice: Circle the best answer (only one). (3 points each)
–2–
14.
a.
Which of the following would be the least stable carbocation?
+
H 2C C CH–CH3
H
b.
+
H 2C C CH3
c.
B
+
H 3C C CH3
H
15. Which of the following would undergo SN2 reaction the fastest?
d.
C
a. CH 3I + HO – Na +
b. CH 3CH2I
+ HO – Na +
c. CH3I + HS – Na +
d. (CH3)2CHI
+ HO – Na +
e. (CH3)2CHI
+ HS – Na +
16. Which of the following alcohols would undergo dehydration the fastest?
A
a. 2-phenyl-2-butanol
b. 2-methyl-2-butanol
c. 2-butanol
d. 1-butanol
17. Which of the following is a not stereospecific reaction?
C
a. epoxidation of cyclohexene with m-CPBA
b. elimination of HBr from 2-bromo-2-methylpropane by sodium ethoxide?
c. dehydration of 1-methylcyclohexanol by heating with H2SO4.
d. reaction of 2-bromobutane with NaOH.
18. Reaction of a secondary alkyl halide with a weak base would likely result in
a. SN1 reaction
b. SN2 reaction
c. E1 Reaction
d. mixture of SN1 and E1
e. E2 elimination
f. mixture of SN2 and E2
19. Which of the following is the stronger acid?
B
a. ethanol
b. ethanethiol
c. acetylene
d. butane
20. Which of the following would be the most soluble in water?
a. diethyl ether
b. methanol
c. 1-butanol
d. dimethylsulfide
–3–
B
D
+
H 3C C CH3
CH3
Syntheses. Give reagents to show how to synthesize the compounds on the right from the compounds
on the left. They may require more than one step. (4 pts each)
21.
1. n-BuLi, I–CH2CH2CH3
H
C
C
H
O
H 3C
C
CH2CH2CH3
2. H2O, H2SO4, HgSO4
22.
1. m-CPBA
OH
OH
2. H2O, H+
V.
Mechanisms. Give a stepwise, detailed mechanism with arrows and intermediates for the
following reactions. (5 points each)
23.
CH3
CH3CH3
H 3C
C
C
CH3
H2SO4
H 3C
heat
OH OH
C
C
O
CH3
H+
CH3CH3
H 3C
C
C
HO
+O
CH3
H
H
CH3
CH3CH3
H 3C
C
H 3C
C CH3
+
C
C
CH3
+
H O CH3
HO
H 2O
–4–
CH3
24.
H+
CH3
O C CH3
CH3
excess HBr
O H
+
CH3
Br C CH3
CH3
why is this not converted to the bromide? C–O bond too strong, and
vinyl cation too unstable
H
O+
CH3
C CH3
CH3
H
O
+
Br
–
CH3
+ C CH3
CH3
25.
HBr
H 3C C C CH3
H+ Br
H 3C
Br
C C
H
CH3
–
Br –
H 3C C C CH3
+
H
Br –
–5–
+
H 3C
CH3
C C
H
Br