Chemistry Question
OC2 Practice 1Name:________________________
___ __
______
Date:________________________
Multiple Choice
____
1. Which of the following is appropriate to include in a synthetic step but should NOT be included in the
mechanism for a reaction?
a. starting materials
d. reaction temperature
b. mechanism arrows
e. necessary reagents
c. products
____
2. Which of the following synthetic steps would be classified as a functional group conversion?
a.
b.
c.
d.
e.
____
3. Fill in the missing precursor to complete the following transform.
a. CH3Br
b. CH3MgBr
c. (CH3)3CMgBr
d. CH3CH2Br
e. CH3CH2MgBr
____
4. Which of the following solvents would NOT be a good choice to use when carrying out the following
reaction?
a. DMSO
b. CH3CH2CH2OH
c. CH3OH
____
d. DMF
e. acetonitrile
5. How do the overall percent yields of the following linear and convergent syntheses compare?
a.
b.
c.
d.
e.
The convergent synthesis has a higher overall percent yield than the linear synthesis.
The linear synthesis has a higher overall percent yield than the convergent synthesis.
Both synthetic schemes result in the same overall percent yield.
It is not possible to determine how yields compare based on the information given.
It depends on how many carbons are in each compound.
____
6. Which molecular orbital has the lowest energy?
a. the highest bonding MO
d. HOMO
b. the highest antibonding MO
e. LUMO
c. the lowest bonding MO
____
7. Which of the following reactions releases the least amount of heat upon hydrogenation?
a. I
b. II
c. III
____
8. Assuming all of the following molecules are planar, which one can be labeled antiaromatic?
a. I
b. II
c. III
____
d. IV
e. V
d. IV
e. V
9. How many electrons are in the following molecule’s largest conjugated pi system?
a. 2
b. 4
c. 6
d. 8
e. 10
____ 10. Which of the following corresponds to the greatest proportion of light absorbed by a sample?
a. 50%T
d. 100%T
b. 75%T
e. 15%T
c. 25%T
____ 11. Which of the electron transitions shown in the figure below would correspond to the UV–vis absorption band
at the shortest wavelength?
a. 1
b. 2
c. 3
d. 4
e. 5
____ 12. Identify the following vibrational mode.
a. symmetric stretch
b. asymmetric stretch
c. out-of-phase bend
d. in-phase bend
e. more than one of the above
____ 13. Which of the following would show a CO stretch at the lowest frequency in its IR spectrum?
a. I
b. II
c. III
d. IV
e. V
____ 14. Which structure is most consistent with the following IR spectrum?
a. I
b. II
c. III
d. IV
e. V
____ 15. Nuclear magnetic resonance spectroscopy is generated using which type of electromagnetic radiation?
a. microwaves
d. gamma rays
b. radio waves
e. No electromagnetic radiation is used.
c. visible light
____ 16. Which hydrogen atom has the greatest chemical shift?
a. HA
b. HB
c. HC
d. HD
e. HE
____ 17. What is the expected splitting pattern for the indicated hydrogen?
a. singlet
b. doublet
c. triplet
d. quartet
e. quintet
____ 18. Which will produce the largest coupling constant?
a. HA coupling to HB
b. HA coupling to HC
c. HB coupling to HC
d. HC coupling to HD
e. HD coupling to HE
____ 19. Which compound would produce the following 1H NMR spectrum?
a. I
b. II
c. III
d. IV
e. V
____ 20. The mass spectrum for an unknown molecule has an M peak with a relative intensity of 100 and an M 1
peak with a relative intensity of 9.905. How many carbons are in the unknown molecule?
a. 1 carbon
d. 10 carbons
b. 5 carbons
e. 100 carbons
c. 9 carbons
Short Answer
1. Briefly explain why the following synthetic step is incorrect, and rewrite it so that it is correct.
2. Determine the alkyl bromide and alkyne that could be used to synthesize the following target molecule.
3. Draw two possible sets of precursors that could be used to synthesize the following target molecule.
4. Calculate the overall percent yield of the following synthetic sequence.
5. Would you expect the following atomic contributor to result in a bonding, antibonding, or nonbonding
molecular orbital? Explain your answer.
6. Is the following compound aromatic, antiaromatic, or nonaromatic? Explain your answer.
7. Draw the symmetric N—H stretch that would occur in the following molecule.
8. Match each compound below to its IR spectrum based on the intensity of the alkane C—H stretch absorption
band
.
9. Which hydrogen in the following molecule has the greatest integration value?
10. How many distinct 13C NMR signals are expected for the following compound?
OC2 Exam 1
Name:______________________
Date:________________________
Multiple Choice (3 pts each)
____1. Which of the following synthetic steps shows a reagent that is written incorrectly?
a.
b.
c.
d.
e.
____2. Which of the following would not alter the carbon skeleton of the starting material?
a.
d.
b.
c.
e.
____3. Fill in the missing precursor to complete the transform below.
a. CH3Br
b. CH3MgBr
c. (CH3)3MgBr
d. CH3CH2Br
e. CH3CH2MgBr
____4. Determine the necessary starting material to complete the step below.
a.
d.
b.
e.
c.
____5. Which atomic orbital contributor has three areas of constructive interference?
a. I
b. II
c. III
d. IV
e. V
____6. Which term can be used to define a molecule that is cyclic, planar, completely conjugated, and has
four π electrons.
a. Aromatic
d. Semiaromatic
b. Antiaromatic
e. None of the above
c. Nonaromatic
____7 Assuming all of the following molecules are planar, which one can be labeled antiaromatic?
a. I
b. II
c. III
d. IV
e. V
____8. How many electrons are in the following molecule’s largest conjugated π system?
a. Two
b. Four
c. Six
d. Eight
e. Ten
____9. What type of electron transition would create an absorption band at the longest wavelength in the
UV–vis spectrum of the molecule below?
a.
d.
b.
e.
c.
____10. If we wished to monitor a frequency to determine whether the reaction below had taken place,
which frequency would be the best choice?
a. 2200 cm–1
b. 1600 cm–1
c. 3300 cm–1
d. 1050 cm–1
e. 2950 cm–1
____11. Which of the following would you expect to have the longest λmax?
a.
d.
b.
c.
e.
____12. How many chemically distinct hydrogen atoms are in the following molecule?
a. Two types
b. Three types
c. Four types
d. Five types
e. Six types
____13. Which hydrogen type has the smallest integration value?
a. HA
b. HB
c. HC
d. HD
e. HE
____14. Which of the following molecules would have a quartet at 3.5 ppm?
a. I
b. II
c. III
d. IV
e. V
____15. The mass spectrum for an unknown molecule has an M+ peak with a relative intensity of 50 and
an M + 1 peak with a relative intensity of 1.65. How many carbons are in the unknown molecule?
a. One carbon
d. Four carbons
b. Two carbons
e. Six carbons
c. Three carbons
Short Answers (5 pts each)
1. A student proposes the following synthesis. Explain why this reaction would not work as intended.
2. A student proposes the following synthetic step. Explain the potential error in this proposed step,
and suggest a better alternative to carry out the desired synthetic transformation.
3. Assume that the following molecule is planar. Use the Frost method to explain whether it is
aromatic, antiaromatic, or nonaromatic. In your Frost diagram, fill in all π electrons, and label the
HOMO and the LUMO.
4. Which is more acidic, HA or HB? Explain.
5. Rank the following bonds in order of increasing stretching vibration frequency. Explain the reason.
6. Assuming all of the following molecules are planar, which one can be labeled antiaromatic, and
why?
7. Explain how coupling constants can be used to determine whether an NMR spectrum represents
compound A or compound B.
8. Draw a splitting diagram for HA and indicate the expected splitting pattern.
.
9. A molecule has the formula C4H9Cl, and its 1H NMR spectrum has only one singlet at 1.49 ppm.
Give the structure of this molecule.
10. Calculate the overall percent yield of the following synthetic sequence.
11. Rank the following in order of increasing C O stretching frequency, and explain the reason.
