Deck 4: Cycloalkanes

Question 1

Which of the following compounds has the highest heat of combustion per CH₂ group?

A) cyclopropane
B) cyclobutane
C) cyclopentane
D) cyclohexane
E) All have equal $\Delta$ H_combustion.

Answer 1

cyclopropane

Question 2

The most stable conformation of cis-1,3-dimethylcyclohexane has how many hydrogen atoms in axial positions?

A) 4
B) 5
C) 6
D) 8
E) None of the above.

Answer 2

6

Question 3

Which of the following correctly shows the Newman projection along a C-C bond in cyclohexane? (the squiggles indicate where the rest of the ring is attached)

A) A
B) B
C) C
D) D
E) E

Answer 3

D

Question 4

Which of the following statements about conformations of methylcyclohexane is true?

A) The energy barrier to interconvert these is too high to be achieved at room temperature.
B) The two forms are in equilibrium and are present in equal amounts at room temperature.
C) The two forms are not in equilibrium but are present in equal amounts at room temperature.
D) The two forms are in equilibrium but are not present in equal amounts at room temperature.
E) The two forms are not in equilibrium and are not present in equal amounts at room temperature.

Question 5

Which of the following isomers would you expect to have the lowest heat of combustion? (i.e.,be most stable)

A) cis-1,2-dimethylcyclohexane
B) trans-1,3-dimethylcyclohexane
C) cis-1,4-dimethylcyclohexane
D) cis-1,3-dimethylcyclohexane
E) All should have the same heat of combustion.

Question 6

Which of the following cyclic alkanes can be ring-opened under hydrogenation conditions?

A) cyclopropane
B) cyclobutane
C) cyclopentane
D) cyclohexane
E) more than one of these

Question 7

Which of the following compounds has the lowest heat of combustion per CH₂ group?

A) cyclopropane
B) cyclobutane
C) cyclopentane
D) cyclohexane
E) All have equal $\Delta$ H_combustion.

Question 8

Which one of the following cyclic alkanes has the greatest tendency to have a planar ring?

A) cyclopropane
B) cyclobutane
C) cyclopentane
D) cyclohexane
E) None of the above are planar.

Question 9

Which would be the most stable conformation of trans-1-methyl-3-isopropylcyclohexane?

A)

B)

C)

D)

E)

Question 10

Which,if either,of the two isomers of the compound shown below would be more stable?

A) Cis is more stable.
B) Trans is more stable.
C) Both are equally stable.
D) Neither is stable.
E) There is no way to predict this.

Question 11

Which of the following disubstituted cyclohexanes could exist in a conformation that has both groups equatorial?

A) cis-1,3-dimethylcyclohexane
B) cis-1,4-dimethylcyclohexane
C) trans-1,3-dimethylcyclohexane
D) cis-1,2-dimethylcyclohexane
E) All or none can have both groups equatorial.

Question 12

What would be the name of the following?

A) 5-cyclopentyl-1-methylcyclononane
B) cis-1-cyclopentyl-5-methylcyclodecane
C) cis-5-methyl-1-cyclopentylcyclododecane
D) trans-cyclopentyl-5-methylcyclodecane
E) (5-methylcyclodecyl)cyclopentane

Question 13

Terpenes can be considered to be built up from what units?

A)

B)

C)

D)

E)

Question 14

Which of the following ring systems belongs to the class of compounds called steroids?

A)

B)

C)

D)

E)

Question 15

What is the correct IUPAC name for the following molecule:

A) 1-ethyl-2-methylhexane
B) 2-ethyl-1-methylcycloheptane
C) 4-ethyl-5-methylcyclohexane
D) 1-ethyl-2-methylcyclohexane
E) 1-methyloctane

Question 16

Which of the following correctly represents cyclopropylcyclohexane?

A)

B)

C)

D)

E) None of the above.

Question 17

Although five- and six-membered rings are generally the most stable,why is cyclopentane less stable than cyclohexane?

A) The angles in cyclopentane deviate significantly from the tetrahedral angle.
B) Five-membered rings have trans annular interactions.
C) Five-membered rings have eclipsing hydrogens.
D) Planar cyclohexane has bond angles closer to 109 $\degree$ .
E) Larger rings are always more stable than smaller rings.

Question 18

Which of the following could have both methyl groups in an equatorial orientation?

A)

B)

C)

D)

E)

Question 19

Which of the following could be classified as a terpene?

A)

B)

C)

D)

E)

Question 20

What would be the proper name of the following:

A) cis-1-tert-butyl-4-methylcyclohexane
B) trans-1-tert-butyl-4-methylcyclohexane
C) axial,equatorial-1-tert-butyl-4-methylcyclohexane
D) cis-1-isopropyl-4-methylcyclohexane
E) trans-1-isopropyl-4-methylcyclohexane

Question 21

Which of the following structures represent cis-1,4-dimethylcyclohexane?

A) I & II
B) I & III
C) II & III
D) All of the above.
E) None of the above.

Question 22

How many isoprene units are in eudesmal?

A) 0
B) 1
C) 2
D) 3
E) Unable to determine

Question 23

What is the correct structure of 2-methyl-1,3-butadiene?

A)

B)

C)

D)

E) None of the above.

Question 24

Which conformation of cyclohexane experiences the most transannular strain?

A) Chair
B) Planar
C) Boat
D) Twist boat
E) All of these are stable.

Question 25

What is the most stable conformation of trans-1-fluoro-4-methylcyclohexane?

A)

B)

C)

D)

E)

Question 26

Steroids frequently function as _____________,which are regulators of biochemical activity.

A) proteins
B) nucleic acids
C) hormones
D) fatty acids
E) triglycerides

Question 27

Which of the following is not in its most stable conformation?

A)

B)

C)

D)

E) All of these are in their most stable conformation.

Question 28

What is the correct name for the following molecule?

A) 1-chloro-2-methyl-4-propylcyclopentane
B) 2-chloro-1-methyl-4-propylcyclopentane
C) 1-chloro-5-methyl-3-propylcyclopentane
D) 5-methyl-1-chloro-3-propylcylopentane
E) 1-chloro-3-propyl-5-methylcyclopentane

Question 29

What is the potential energy change to convert from a twist-boat to boat conformation?

A) -14 Kcal/mol
B) 0 Kcal/mol
C) 1.4 Kcal/mol
D) 14 Kcal/mol
E) 45 Kcal/mol

Question 30

Cyclohexanes exhibit a higher_______than their straight-chain analogs.(Choose the correct answer)

A) boiling point
B) melting point
C) density
D) All of these are correct.
E) Two of these are correct.