CHE 275 ALKANES AND CYCLOALKANES CHAP 3 ASSIGN ...

CHE 275 ALKANES AND CYCLOALKANES CHAP 3 ASSIGN
COMFORMATIONS AND cis-trans STEREOISOMERS
1. Which of the following Newman projections represents "sighting down" the C4-C5 bond of 4,5-di-isopropyloctane in the
conformation in which the two isopropyl groups are anti with respect to each other?
A. B.
C. D.
E.
2. To which conformation of butane would the position marked with an asterisk in the following energy diagram correspond?
A B C D E
3. What molecule does the Newman projection shown correspond to?
A. butane
B. pentane
C. 3-methylbutane
D. 2-methylbutane
E. isobutane
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4. Which of the following Newman Projections represents the lowest energy conformation for butane?
A. B.
C. D.
E.
5. Choose the zigzag structure that corresponds to the molecule depicted in the following Newman projection.
A B C D E
6. Which of the following would be the Newman projection of a C-C bond in chair cyclohexane?
A. B.
C. D.
E.
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7. Which of the following isomers of the formula C 8 H 14 would you expect to give the highest heat of combustion?
A. B. C. D. E.
8. What would be the best name for the following compound? (Neglect any cis-trans isomerism that is possible.)
A. 1-ethyl-3,4-dimethylcyclohexane
B. 3-ethyl-1,6-dimethylcyclohexane
C. 1-ethyl-4,5-dimethylcyclohexane
D. 5-ethyl-1,2-dimethylcyclohexane
E. 4-ethyl-1,2-dimethylcyclohexane
9. Which of the following cyclic alkanes is the most stable (i.e., lowest energy)?
A. B. C. D. E.
10. What is the lowest energy stereoisomer of cis-1-isopropyl-3-methylcyclohexane?
A. B.
C. D.
E.
11. Which of the following most accurately illustrates the correct geometry of the axial and equatorial bonds in the chair
conformation of cyclohexane?
A B C D E
12. What is the correct IUPAC name for the following molecule?
A. trans-3-methyl-5-ethylcyclohexane
B. cis-3-methyl-5-ethylcyclohexane
C. trans-1-ethyl-3-methylcyclohexane
D. cis-1-ethyl-3-methylcyclohexane
E. trans-1-methyl-3-ethylcyclohexane
13. What is the most stable conformation of trans-1-tert -butyl-2-methylcyclohexane?
A B C D E
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14. In the following chair conformation of methylcyclohexane, which hydrogen (indicated by arrows) causes the greatest steric
strain with the axial methyl group? This conformation (with the methyl group occupying an axial orientation) is less stable
than the conformation in which the methyl group is equatorial.
A. B.
C. D.
E.
15. What is the most stable conformation of cis -1-sec-butyl-4-methylcyclohexane?
A B C D E
16. How many axial hydrogens are present in the following molecule?
A. two
B. three
C. four
D. five
E. six
17. Cyclobutane is an example of a molecule that shows
A. only angle strain B. 109.5° bond angles
C. angle and torsional strain D. only torsional strain
E. a low energy ring structure
18. Consider the graph of total strain energy versus ring size. Which of the following statements is false?
A. Among the smaller ring sizes, six-membered rings are the most stable.
B. Medium-sized rings (7-11 carbons) are less stable than larger rings.
C. Five-membered rings have about the same strain energy as seven-membered rings.
D. Four-membered rings are significantly more stable than three-membered rings.
E. Ten-membered rings are the least stable of the medium-sized rings (7-11 carbons).
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19. Which of the following definitions most accurately describes stereo-isomers?
A. compounds that differ from one another by one bond rotations
B. compounds that differ from one another as a result of differences in spatial orientation that are caused by altering their
connectivity (one structure compared with the other)
C. compounds that have exactly the same connectivity but differ in the arrangement of their atoms in space
D. compounds that are very similar in structure but contain several different functional groups
E. compounds that have the same number of carbon atoms but differ because one of them is acyclic (no ring) and the other
is cyclic (contains a ring)
20. Which one of the following statements is incorrect?
A. Cyclopropane has a higher heat of combustion than does cyclohexane.
B. Cyclopentane is destabilized somewhat by tortional (eclipsing) interactions.
C. Cyclohexane exists predominantly in an all-staggered conformation.
D. Cyclopropane is destabilized by both angle strain and tortional (eclipsing) interactions.
E. Cyclobutane has a higher heat of combustion per CH 2 group than does cyclohexane.
21. Which conformation of cis -1-isopropyl-4-methylcyclohexane would be of the lowest energy?
A. B.
C. D.
E.
22. Cyclopentane exhibits more torsional strain than cyclohexane because,
A. cyclopentane exists predominantly in the boat form.
B. its atoms are in a partially eclipsed conformation.
C. its atoms are in the staggered conformation.
D. its bond angels deviate greatly from 109°.
23. trans-1,2-Dibromocyclohexane is represented by structure(s):
A. I
B. II
C. III
D. II and III
E. I and II
24. What is the correct name of the following compound?
A. 1-Chlorobicyclo[4.1.1]octane
B. 2-Chlorobicyclo[4.1.0]octane
C. 2-Chlorobicyclo[4.1.1]octane
D. 2-Chlorobicyclo[4.1.1]heptane
E. 5-Chlorobicyclo[4.1.1]octane
Br
H
Br
H
H
Br
Br
H
H
I II III
Cl
Br
Br
H
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25. Which of the following is bicyclo[3.2.2]nonane?
A. I
B. II
C. III
D. IV
E. V
I II III
26. cis-1,3-Dibromocyclohexane is represented by structure(s):
A. I
B. II
C. III
D. II and III
E. I and II
Br
H
IV V
Br
Br
H
H
Br
H H
Br
Br
H
I II III
27. The preferred conformation of cis-3-tert-butyl-1-methylcyclohexane is the one in which:
A. the tert-butyl group is axial and the methyl group is equatorial.
B. the methyl group is axial and the tert-butyl group is equatorial.
C. both groups are axial.
D. both groups are equatorial.
E. the molecule exists in a boat conformation.
28. Which of the following can be described as cis isomers?
A. I
B. II, V
C. III, IV
D. I, III and IV
E. None of the above are cis isomers.
HO
Br Cl
Br
CH 3
F
I II III
CH
CH 3
3
HO
CH 2 CH 3
IV V
29. Which of the following will have the same energy after undergoing ring flip?
A. I
B. II
C. III
D. IV
E. V
HO
OH
Cl
CH 3
I II III
F
Br
HO
CH 3
CH 2 CH 3
CH 2 CH 3
IV V
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30. Which of these C 10 H 18 isomers is predicted to be the most stable?
A. I
B. II
C. III
D. IV
E. V I II III
H
H
H
IV
H
V
EXTRA CREDIT
31. The most stable conformation for 1,2-ethanediol (ethylene glycol) is shown below. It is the most stable conformation
because:
A. this corresponds to an anti conformation.
B. in general, gauche conformations possess the minimum energy.
C. it is stabilized by intramolecular hydrogen bonding.
D. it is a staggered conformation.
E. it has the highest energy of all the possibilities.
H
H
H
H
OH
OH
32. The most stable conformation of 2,3-dibromobutane, viewed through the C-2—C-3 bond :
A. I
B. II
C. III
D. IV
E. V
Br
Br
CH 3
H
H
H
H 3 C Br
H
Br
H 3 C Br
CH 3
H
I II III
H 3 C
Br
H
H
Br
H 3 C
Br
H
Br
CH 3
H 3 C
H H 3 C
Br
CH 3
IV V
H
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NAME_______________________________________
DATE______________
ANSWER SHEET
CHE 275 – CHAP 3 ASSIGN
1. _______________ 11. _______________ 21. _______________ 31. _______________
2. _______________ 12. _______________ 22. _______________ 32. _______________
3. _______________ 13. _______________ 23. _______________ 33. _______________
4. _______________ 14. _______________ 24. _______________ 34. _______________
5. _______________ 15. _______________ 25. _______________ 35. _______________
6. _______________ 16. _______________ 26. _______________ 36. _______________
7. _______________ 17. _______________ 27. _______________ 37. _______________
8. _______________ 18. _______________ 28. _______________ 38. _______________
9. _______________ 19. _______________ 29. _______________ 39. _______________
10. _______________ 20. _______________ 30. _______________ 40. _______________
SSI 2013
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