Chemistry 2411
Clower
Assignment 3: 12 points
Due March 18, 2014
Name ___________________________________
1. Which of the following statements is a correct description of the most stable conformation of
1,1,3-trimethylcyclohexane?
A. The methyl group at C-3 is equatorial.
B. C-1 is a tertiary carbon and C-3 is a primary carbon.
C. C-1 is a quaternary carbon and C-3 is a secondary carbon.
D. C-1 is a tertiary carbon and C-3 is a secondary carbon.
E. Both methyl groups at C-1 are equatorial.
2. Which of the statements below correctly describes the chair conformations of trans-1,4dimethylcyclohexane?
A. The two chair conformations are of equal energy.
B. The higher energy chair conformation contains one axial methyl group and one
equatorial methyl group.
C. The lower energy chair conformation contains one axial methyl group and one equatorial
methyl group.
D. The higher energy chair conformation contains two axial methyl groups.
E. The lower energy chair conformation contains two axial methyl groups.
3. Identify this conformation of butane:
A. Gauche
B. Eclipsed
C. Anti
H
H
CH3
H
CH3
H
4. What is the difference between the C-C-C angles of a planar, hexagonal cyclohexane ring
and the chair structure of the actual cyclohexane molecule?
A. 120.0° in a planar hexagon; 109.5° in cyclohexane
B. They are the same in both: 120.0° in a planar hexagon; 120.0° in cyclohexane
C. They are the same in both: 109.5° in a planar hexagon; 109.5° in cyclohexane
D. 109.5° in a planar hexagon; 120.0° in cyclohexane
5. Which of the following is produced by an axial methyl group of methylcyclohexane?
A. one 1,2-diaxial interaction
B. two 1,2-diaxial interactions
C. one 1,3-diaxial interaction
D. two 1,3-diaxial interactions
6. In the lowest energy conformation of the compound below, how many alkyl substituents are
axial?
A. 0
CH3
B. 1
C. 2
D. 3
(CH3)2CH
CH2CH3
Chemistry 2411
Clower
Assignment 3: 12 points
Due March 18, 2014
Name ___________________________________
7. The structures to the right are:
A. conformations of the same compound.
B. cis-trans stereosisomers.
C. constitutional isomers.
D. conformations and constitutional isomers.
E. none of the above.
CH3
H
H
H
H
H
CH3
H
H
CH3
H
CH3
8. The structures to the right are:
A. conformations of the same compound.
B. cis-trans stereosisomers.
C. constitutional isomers.
D. conformations and constitutional isomers.
E. none of the above.
9. Which of the following statements concerning the conformations of butane is true?
A. Unlike ethane, all butane conformations are classified as eclipsed.
B. The lowest energy conformation of butane is the gauche conformation.
C. There is more torsional strain in the anti conformation than in the eclipsed conformations.
D. All eclipsed conformations have the same amount of steric strain.
E. The gauche and anti conformations differ primarily in the amount of steric strain present.
10. The energy barrier for carbon-carbon bond rotation in propane is mainly due to __________.
A. angle strain
B. bond strain
C. muscle strain
D. steric strain
E. torsional strain
11. Define angle strain in your own words. Which cycloalkanes exhibit angle strain?
12. Consider the structure of cyclohexane below.
H
H
(a) What is the name of this conformation?
H
H
H
H
(b) Circle all the equatorial hydrogens.
H
H
H
H
H
H
Chemistry 2411
Clower
Assignment 3: 12 points
Due March 18, 2014
Name ___________________________________
13. Draw Newman projections for the (a) most and (b) least stable conformations of butane.
Label each as staggered or eclipsed.
14. D-Pinitol is an interesting hexahydroxy cyclohexane, whose structure is shown below.
(a) On the templates below, draw the two chair conformations that are in equilibrium for Dpinitol. Be sure to clearly indicate which substituents are axial and which are equatorial.
(b) Circle the most stable conformation.
6
4
5
3
2
1