CHE 230-002 Organic Chemistry Exam 3, Fall 2011
Name ________________________________ Student ID No. ___________________
Before you begin this exam:
First: You are allowed to have writing utensils and a simple model set at your
seat. Please put away all other materials. Second: Place your student
identification on your desk. A proctor will come around to check everyone’s ID.
Third: Read through the entire exam. Your goal, as always, is to score as many
points as possible. Do not waste time on problems that you can’t do if there are
others that look easy. Fourth: Read each question carefully. Be sure you answer the
question that is asked. If you erase something, make sure it is very clear what is on
erased and what you intend to include in your answer. Fifth: Once the start time
is announced, you will have one hour to complete this exam. There will be no
extensions, so budget your time carefully.
Problem Number
Points Possible
Score
1.
10
_____________
2.
30
_____________
3.
10
_____________
4.
15
_____________
5.
20
_____________
6.
15
_____________
7.
15
_____________
8.
15
_____________
9.
10
_____________
10.
30
_____________
11.
30
_____________
Total
200
_____________
1
1. (10 points) In the boxes provided below, draw the resonance hybrid for
each of the structures below. Don’t forget to show lone pairs and partial charges
where appropriate. Circle the sp2-hybridized atoms in the structures provided
(not in your hybrid).
O
!-
O !+
!-
!-
2. (30 points) Identify the number of peaks in the 1H and 13C NMR spectra for
the following molecules.
Cl
O
O
1H
13C
5
4
3
NMR
3
NMR
3
4
3. (10 points) Fill in the blank for the following acid/base equilibrium reaction
between phenol and cyclohexanol.
O
OH
OH
O
+
+
The molecule with the most acidic proton is phenol.
The equilibrium lies to the left.
The most important phenomenon contributing to the pKa difference between the
two molecules is resonance.
2
4. (15 points) In each molecule drawn below, circle the most acidic proton. In
some cases, there may be more than one equivalent answer, but if so, you only
need to circle one H.
NH2
CH
H2C
H2C
HO
CH2
H
C
CH2
H2
C
H
C
H
C
C
CH3
HC
C
C
H
OH
H
C
CH
H2
C
O
CH
C
H2
H3C
C
C
OH
CH3
Bonus: 5 points! Circle the most acidic protons in the molecule below, and briefly state
the reason for your choice within the box provided.
The protons I've circled in the molecule to
the left are more acidic because:
BONUS!
O
O
C
C
H3C
C
H2
there is greater resonance stabilization
in the resultant anion than in in anion
that results from deprotonation of the
methyl group
CH3
5. (20 points) In the box provided, draw the skeletal structures for the products
(organic and inorganic) of the following reaction by following the curved arrows.
H
H
C
H
Cl
+
3
HCl
6. (15 points) Given the reaction energy diagram below:
Insert the appropriate letters for each of the following:
(1) the transition state for the slowest step in the reaction: B
(2) the product of the reaction: G
(3) the most stable reaction intermediate: C
7. (15 points) In the box provided below, draw the transition state for the each
of the following reactions.
H
CH3Br
+
–OH
CH3OH
+
Br–
!-
OH !-
Br
H
H
+
+ HBr
+BrH–
4
!+
!Br
H
8. (15 points) In each series below, circle the following:
a) the molecule that is most reactive in an SN1 reaction:
Br
Br
Br
Br
b) the anion that is most reactive as a nucleophile:
CH3–
–
–
OH
NH2
F–
I–
F–
c) the best leaving group:
Br–
Cl–
9. (10 points) When 3-chloro-3-methylpentane is treated with a variety of strong
bases, the products always contain two isomers A and B with chemical formula
C6H12. The 13C NMR spectrum of isomer A has 4 peaks, and the 13C NMR of
isomer B has 6 peaks. Draw the skeletal structures of products A and B of this
elimination reaction in the boxes below.
base
or
Cl
product A: C6H12 with 4 peaks
in its 13C NMR spectrum
5
product B: C6H12 with 6 peaks
in its 13C NMR spectrum
10. (30 points) Draw the skeletal structure of the organic product(s) of the
following substitution reactions, indicating stereochemistry where relevant. If
more than one major product is formed, draw both isomers.
an SN2 reaction:
NaCN
+
CN
Cl
an SN1 reaction:
OH
Br
+
H2O
+
OH
an SN2 reaction:
Br
+
S
S
6
11. (30 points) For each set of spectral data below, draw the skeletal structure of
the molecule consistent with the data in the box provided.
C5H10O2
IR peak at 1740 cm−1
1
H NMR (ppm): 1.15 (triplet, 3 H); 1.25 (triplet, 3 H); 2.30 (quartet, 2 H); 4.72
(quartet, 2 H)
O
O
C6H14O
IR peak at 3000–2850 cm−1
1
H NMR: 1.10 ppm (doublet); 3.60 ppm (septet)
O
C4H8 Br2
IR peak at 3000–2850 cm−1
1
H NMR: 1.87 ppm (singlet, 6 H); 3.86 ppm (singlet, 2 H)
Br
Br
END OF EXAM
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