1st Semester Organic Chemistry (Org Chem I)
Final Exam, May 23rd
Name:
Recitation Instructor:
Instructions
1. Keep the exam closed until you are instructed to begin.
2. The exam consists of 10 questions in 13 pages (including this one). The first thing you should do is
make sure that no pages are missing. If a page is missing, notify a proctor immediately.
3. You will have 2 hours to complete the exam, at which time pens must be put down. Budget your time
wisely. Don’t write in pencil!
4. Questions are ranked easy (*), medium (**), and hard (***). You probably shouldn't spend too much
time on a hard question if you still have easy or medium difficulty problems you haven't tried yet.
4. Make sure to show all of your worth and make it clear what your thought process was. Answers
should fit in the space provided. If you need to use the back of the sheet of paper, you must make note
of it in the space allotted for credit.
5. GOOD LUCK!
Breakdown: Question (total points):
1a (7.5)
1b (7.5)
2 (7)
3a (6.5)
3b (3)
3c (3)
3d (3)
3e (3)
3f (5.5)
4 (7)
5a (7.5)
5b (7.5)
6 (7)
8 (5)
8 (4)
9a (7.5)
9b (7.5)
10 (7)
Total = 107 pts (7 extra points included!)
1 1. NMR spectra (*) 15 points. Below you have an expansion of the 1H NMR for isobutanol (2methylpropan-1-ol). The 13C (H decoupled) spectrum (A) is also provided together with a DEPT
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C spectrum (B).
1a. 7.5 pts. Below you have the 1H NMR spectrum for isobutanol (2-methyl propan-1-ol). The
numeric values above the peaks are the integration (area of the peak) values.
Explain intensity and splitting pattern (multiplicity) for each peak:
Peak at δ 0.90 ppm:
2 Peak at δ 1.75 ppm:
Peak at δ 2.90 ppm:
Peak at δ 3.40 ppm:
b) 7.5 pts. Below you have two types of
A and B.
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C NMR spectra for isobutanol (2-methyl propan-1-ol)
A. 13C (H decoupled) spectrum of isobutanol in CDCl3. Peaks at δ: 19, 30, 68 and 76 ppm.
3 Write clearly in this spectrum how you assign the different carbon atoms to the signals (e.g.
mark the signal that can be assigned to a CH3 group). DO NOT FORGET THE PEAK FROM
CDCl3! Looking at spectrum B will help you out.
B. DEPT 13C (H decoupled) spectrum (B) of isobutanol (2-methyl propan-1-ol). Peaks at δ: 19,
30, 68 (negative) ppm. Note that peak at 76 ppm is absent here.
2. Conformational analysis 1 (**) 8 pts. For the compound below, draw both chair
conformations of the following molecule and discuss the relative energies.
OH
HO
O
OH
HO
OH
4 3. Reactivity Questions (*, ** and ***) 25 points.
Give the products or missing reactants for the following reactions. Include stereochemistry. That
means that some boxes may allocate more than one product. If that’s the case you can draw
the other(s) product(s) in the blank space close by (or below).
3a. 7.5 pts.
3b. 3 pts
3c. 3 pts 5 3d. 3 pts
3e. 3 pts
3f. 5.5 pts
D = Deuterium 2H
6 4. Halogenation reactions II (**) 7 points. a) Circle the reaction that is more regioselective (A or B)
and explain why. Hint: think of possible products. b) How many fractions will be obtained by distillation
in each case?
5.Synthesis (**) 15 points (7.5 each).
5a. 7.5 pts. Provide a synthesis of the aldehyde below starting with cyclopentene and any other organic
compound having four or fewer carbon atoms. You may use any inorganic compound you need.
7 5b. 7.5 pts. Provide the synthesis of the product below starting from 2-propanol as the source of all
carbon atoms. You can use inorganic compounds and solvents as needed.
2-hexyne
8 6. Mass Spectrometry (**) 7 points. An MS spectrum (electronic ionization) of 3-methyl-2pentanone is provided below. Identify: a) 1 pt The molecular ion peak and the base peak in this
spectrum; b) 5 pts Draw the molecular structure corresponding to the peaks at m/z of 43, 58, 85
and 100.
9 7. Substitution reactions (**) 4 points. Below you have two energy coordinate diagrams (A and B). In
substitution reactions the reactants are R-X + Nucleophile (Nu-) while the products are R-Nu + X-.
Indicate which reaction coordinate diagram goes with an SN1 type mechanism and which one with an
SN2 type mechanism briefly explaining why.
A
B
8. IR spectroscopy (*) 5 points. Circle which of the following bonds (circled) gives the weakest
absorbance in the infrared spectrum.
O
H
C
H3C
CH2
1
H3C
CH3
2
C
CH3
H3C
3
O
4
10 9. Reaction mechanisms (**). 15 pts. Propose a reasonable mechanism for these reactions. Use
curved arrows consistently
9a. (7.5 pts)
11 9b. (7.5 pts)
12 10. Stereochemistry. (7 pts) The compound below is called ephedrine, a chiral compound isolated
from the plant ephedra sinica (IUPAC name: 2-(methylamino)-1-phenylpropan-1-ol). a) Draw a
Newman projection for the molecular structure below. b) Assign the absolute configuration of carbons 1
and 2 (you can choose your preferred projection in order to do this).
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