CHE 2202, Section 101
Spring 2014
Exam IA
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1. Use the data below to answer the following questions. Show your work:
 Mass spec: parent ion at m/z = 100
 IR: stretches at 3018, 2980, 2947, 1720 cm-1
a. (9 points) Draw the structure.
b. (3 points) There is a major fragment observed at m/z = 85. What is likely lost from the parent
ion to produce this fragment?
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/ 12 points
2. (4 points) Which of the following would show two signals in its 1H NMR spectrum? Circle
all that apply.
3. (4 points) Rank the 13C NMR chemicals shifts of the carbons in the following compounds
from most downfield (=1) to most upfield (=4).
4. (4 points) Circle the correct relationship between the two hydrogens in bold in the following
structure.
a. homotopic
b. enantiotopic
c. diastereotopic
d. no relationship
5. (2 points) Based on your answer to number 4, would the two hydrogens in bold give the same
signal or different signals in the 1H NMR spectrum? Circle the correct choice.
Same signal
Different signals
/ 14 points
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6. (14 points) The following compounds are isomers of each other. Fill in the table below to
discuss if and how these structures could be differentiated from each other by 1H NMR and mass
spectrometry.
Structures
Number of signals present
Chemical shifts present
(provide general ranges)
Integration ratio
Splitting patterns
Parent ion value
Fragments Observed from
Alpha-Cleavage
Fragments Observed from
McLafferty Rearrangement
7. (4 points) What is the significance of the base peak in a mass spectrum? Circle the correct
answer.
a. It gives the m/z value for the unfragmented structure.
b. It differentiates the radical cation from the radical.
c. It is the tallest peak.
d. It is the peak with the largest m/z value.
/ 18 points
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8. Consider the following reaction:
a.) (2 points) Circle the kinetic product in the reaction scheme above.
b.) (6 points) Draw a reaction coordinate diagram for the reaction above that illustrates the
reaction progress from starting material X to products A and B. Use a solid line (
) to
show the formation of A and a dashed line (-------) to show the formation of B.
c.) (3 points) If you are trying to maximize the formation of the kinetic product and minimize
the formation of the thermodynamic product, which conditions would be best? Circle your
answer.
a.) 85 °C, 24 h
b.) room temperature, 5 h
c.) 0 °C, 1.5 h
9. (3 points) Ethanol, methanol, and cyclohexane are commonly used as solvents for UV-vis
spectroscopy because they do not absorb radiation at wavelengths longer than 200 nm. Why
not?
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/ 14 points
10. (6 points) Azulene is a blue substance, β-carotene is an orange-red color, and 1,3cyclohexadiene is colorless.
Based on the colors of these compounds, draw lines to match each compound to its λmax value.
Azulene
259 nm
β-Carotene
497 nm
1,3-Cyclohexadiene
696 nm
11. (16 points) Fill in the boxes with the missing starting materials or products for the DielsAlder reaction.
pts / 22 pts
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12. (10 points) Circle the aromatic molecules. For those that are not circled, indicate why these
are not aromatic.
13. (4 points) Most diazocompounds are exceedingly, and sometimes disastrously, unstable.
However, diazocyclopentadiene is quite stable. Explain, using structures, its stability.
14. (6 points) Draw a structure of an aromatic compound that:
a. is made of carbon and hydrogen only, and has 3 rings.
b. contains one boron atom in addition to carbons and hydrogens, and has one ring.
/ 20 points
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