Question 1

Which of the following best describes the molecular formula for a cycloalkane with 7 carbon atoms?

Accepted Answer

$$\mathrm{C}_7\mathrm{H}_{14}$$

Question 2

Which type of strain is primarily responsible for the instability of cyclopropane compared to cyclohexane?

Accepted Answer

Angle strain

Question 3

A cyclohexane ring is most stable in which conformation, and why?

Accepted Answer

Chair, because it minimizes both angle and torsional strain

Question 4

What is the IUPAC name for a cycloalkane with a single methyl group attached to a five-membered ring?

Accepted Answer

Methylcyclopentane

Question 5

Which of the following statements about the chair conformation of cyclohexane is TRUE?

Accepted Answer

There are six axial and six equatorial hydrogens

Question 6

A methyl group is attached to a cyclohexane ring. Which conformation is more stable and why?

Accepted Answer

Equatorial, due to minimized 1,3-diaxial interactions

Question 7

Which of the following best explains why cyclobutane is not planar?

Accepted Answer

To reduce torsional strain from eclipsed hydrogens

Question 8

Given the following energy differences, which conformation of methylcyclohexane is favored at equilibrium and by how much energy?

Accepted Answer

Equatorial, by 7.6 kJ/mol

Question 9

Which of the following is the correct general formula for alkanes?

Accepted Answer

$$\mathrm{C}_n\mathrm{H}_{2n+2}$$

Question 10

Which of the following best describes the main source of ring strain in cyclopropane?

Accepted Answer

Deviation from the ideal tetrahedral angle of $$109.5^\circ$$

Question 11

A cyclohexane ring undergoes a chair flip. What happens to the positions of axial and equatorial substituents?

Accepted Answer

Axial groups become equatorial and vice versa

Question 12

Which of the following is a correct statement about cis-1,2-dimethylcyclohexane?

Accepted Answer

Each chair conformation has one axial and one equatorial methyl group

Question 13

Which of the following best describes the structure of Buckminsterfullerene ($$\mathrm{C}_{60}$$)?

Accepted Answer

A spherical molecule composed of fused pentagons and hexagons

Question 14

Which of the following is true about the energy diagram for cyclohexane conformations?

Accepted Answer

The chair conformation is the most stable, while the half-chair is the least stable

Question 15

Which of the following best explains why cyclopentane adopts a slightly bent conformation rather than being planar?

Accepted Answer

To reduce torsional strain from eclipsed hydrogens

Question 16

Which of the following is a correct statement about 1,3-diaxial interactions in substituted cyclohexanes?

Accepted Answer

They are minimized when the substituent is in the equatorial position

Question 17

Which of the following best describes the difference between cis- and trans-1,4-disubstituted cyclohexanes?

Accepted Answer

Cis isomers have both substituents on the same side of the ring; trans isomers have them on opposite sides

Question 18

Which of the following is the correct formula for the heat of combustion difference used to calculate cycloalkane strain energies?

Accepted Answer

$$\Delta E = (	ext{Cycloalkane heat of combustion per CH}_2 - 	ext{Acyclic alkane heat of combustion per CH}_2) 	imes 	ext{number of CH}_2 	ext{ units}$$

Question 19

Which of the following is a correct statement about the numbering of substituents in substituted cycloalkanes?

Accepted Answer

The ring is numbered to give the substituents the lowest possible numbers

Alkanes and Cycloalkanes: Structure, Nomenclature, and Conformations

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