Deck 4: Organic Compounds: Cycloalkanes and Their Stereochemistry

Question 1

Which of the following statements is not true regarding the conformation of substituted cyclohexanes?

A)ring flip of substituted cyclohexanes flips the axial and equatorial positions of substituents
B)substituted cyclohexanes are destabilized by 1,3-diaxial interactions
C)the twist-boat conformation of cyclohexane is more stable than the chair conformation
D)the relative amount of two conformations of substituted cyclohexanes can be determined from the difference in strain energy

Answer 1

the twist-boat conformation of cyclohexane is more stable than the chair conformation

Question 2

Which of the following structures represents trans-1,2-dimethylcyclohexane?

A)
B)
C)
D)

Answer 2

Question 3

Substitution of which of the following groups on a cycloalkane would result in the greatest amount of steric strain?

A)bromo
B)ethyl
C)isopropyl
D)hydroxyl

Answer 3

isopropyl

Question 4

Which one of the following structures represents a different compound from the other three?

A)
B)
C)
D)

Question 5

Which of the following cycloalkanes would be the most similar to its open chain counterpart?

A)cyclodecane
B)cyclooctane
C)cyclopentane
D)cyclopropane

Question 6

Which of the following is the most stable conformation of trans-1-ethyl-3-methylcyclohexane?

A)
B)
C)
D)

Question 7

D-Pinitol is an interesting hexahydroxycyclohexane,whose structure is shown below.
On the templates provided,draw the two chair conformations that are in equilibrium for D-pinitol.Circle the most stable conformation.

Question 8

Which of the following structures represents trans-1,3-dimethylcyclohexane?

A)
B)
C)
D)

Question 9

Which one of the following structures represents a different compound from the other three?

A)
B)
C)
D)

Question 10

If the 1,3-diaxial strain for an ethyl group is 4.0 kJ/mol,what is the energy difference between the axial and equatorial conformations of ethylcyclohexane?

A)2.0 kJ/mol
B)4.0 kJ/mol
C)8.0 kJ/mol
D)16.0 kJ/mol
E)Cannot be determined from the 1,3-diaxial strain

Question 11

Which of the following is the most stable conformation of cis-1-isopropyl-3-methylcyclohexane?

A)
B)
C)
D)

Question 12

Which of the following compounds can adopt a chair conformation in which there are no axial methyl groups?

A)1,1-dimethylcyclohexane
B)cis-1,2-dimethylcyclohexane
C)trans-1,2-dimethylcyclohexane
D)trans-1,3-dimethylcyclohexane

Question 13

Which of the following cycloalkanes has the most ring strain?

A)cyclopropane
B)cyclobutane
C)cyclopentane
D)cyclohexane

Question 14

Instructions: (-)-Menthol is responsible for the characteristic flavor and taste of peppermint.The structure of (-)-menthol is shown below.Use this information to answer the following question.


Refer to instructions.On the chair template provided below,draw the two chair conformations that are in equilibrium for (-)-menthol.

Question 15

In cycloheptane,which of the following factors contributes the least to the stability of the ring conformation?

A)torsional strain
B)angle strain
C)steric strain
D)all of these contribute to an approximately equal degree

Question 16

In which of the following compounds would the carbon-carbon bond angle diverge the greatest from 109 ^$\circ$ ?

A)cyclodecane
B)cyclooctane
C)cyclopentane
D)cyclopropane

Question 17

If cyclohexane were planar,how much torsional strain would be present in the planar molecule? Assume that the energy cost for each H«H eclipsing interaction is 4.0 kcal/mol.

A)12.0 kJ/mol
B)24.0 kJ/mol
C)36.0 kJ/mol
D)48.0 kJ/mol
E)64.0 kJ/mol

Question 18

What is the energy difference between the two chair conformations of the following compound that is due to steric strain?
Cis-1-bromo-4-isopropylcyclohexane

A)7.2 kJ/mol
B)5.6 kJ/mol
C)9.2 kJ/mol
D)11.2 kJ/mol