Question 1

Identify the least stable conformation for 1-tert-butyl-3-methylcyclohexane.

Accepted Answer

The least stable conformation for 1-tert-butyl-3-methylcyclohexane is when both the tert-butyl and methyl groups are in the axial positions (B). This configuration creates the most steric hindrance and destabilizes the molecule due to increased 1,3-diaxial interactions.

Question 2

The K_eq for the interconversion for the two chair forms of methylcyclohexane at 25 °C is 18.What % of the chair conformers feature an axial methyl group?

Accepted Answer

The equilibrium constant (K_eq) for the interconversion of the two chair forms of methylcyclohexane is given as 18. This means that the ratio of the more stable equatorial conformer to the less stable axial conformer is 18:1. Since the axial conformer is less stable, it is less populated. To find the percentage of the axial conformer, we calculate the fraction of the axial conformer in the total population (1 part axial out of 19 total parts, since 18 parts are equatorial and 1 part is axial). Thus, (1/19) * 100% = approximately 5%.

Question 3

Which of the following describes the most stable conformation of trans-1-tert-butyl-3-methylcyclohexane?

Accepted Answer

The most stable conformation of a cyclohexane molecule has its larger groups in the equatorial positions to avoid steric hindrance with neighboring groups. In this case, the tert-butyl group is bulkier than the methyl group, therefore the tert-butyl group should be placed in the equatorial position while the methyl group occupies the axial position. This way, there is less steric strain between the groups compared to the other possible conformations.

Question 4

What aspect of the fused ring systems present in cholesterol make it an ideal compound to lend rigidity to cell membranes?

Accepted Answer

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Question 5

Draw the chair conformer of cyclohexane.Label the axial hydrogens (H_a)and the equatorial hydrogens (H_e).

Accepted Answer

The answer of Draw the chair conformer of cyclohexane.Label the...

Question 6

The equilibrium constant for the ring-flip of fluorocyclohexane is 1.5 at 25°C.Calculate the percentage of the axial conformer at the temperature.

Accepted Answer

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Question 7

Draw the most stable conformation of trans-1-tert-butyl-3-methylcyclohexane.

Accepted Answer

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Question 8

Draw the most stable conformation of trans-1-isopropyl-2-methylcyclohexane.

Accepted Answer

The answer of Draw the most stable conformation of trans-1-isopropyl-2-methylcyclohexane....

Question 9

Draw the most stable conformer of cis-1-isopropyl-2-methylcyclohexane.

Accepted Answer

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Question 10

Identify the number of secondary hydrogens in the following structure.

Accepted Answer

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Question 11

Draw the most stable conformer of trans-1-ethyl-4-methylcyclohexane.

Accepted Answer

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Question 12

Draw the most stable conformer of trans-1-ethyl-2-methylcyclohexane.

Accepted Answer

The answer of Draw the most stable conformer of trans-1-ethyl-2-methylcyclohexane....

Question 13

Draw the most stable conformer of trans-1-ethyl-3-methylcyclohexane.

Accepted Answer

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Question 14

Draw the most stable conformer of cis-1-ethyl-3-methylcyclohexane.

Accepted Answer

The answer of Draw the most stable conformer of cis-1-ethyl-3-methylcyclohexane....

Question 15

Which conformer is at a local energy minimum on the potential energy diagram in the chair-chair interconversion of cyclohexane?

Accepted Answer

The twist-boat conformer is at a local energy minimum in the chair-chair interconversion of cyclohexane, as it is more stable than the boat and half-chair conformers but less stable than the chair conformer.

Question 16

Which of the following has two equatorial alkyl substituents in its most stable conformation?

Accepted Answer

The answer of Which of the following has two equatorial...

Question 17

Name the compound shown below.

Accepted Answer

The answer of Name the compound shown below. 
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Question 18

Draw the most stable conformer of cis-1-ethyl-4-methylcyclohexane.

Accepted Answer

The answer of Draw the most stable conformer of cis-1-ethyl-4-methylcyclohexane....

Question 19

Identify the compound where the groups are axial and equatorial.

Accepted Answer

In cis-1,4-dibromocyclohexane, one bromine is axial and the other is equatorial when the cyclohexane ring is in the chair conformation.

Question 20

Draw the most stable conformer of cis-1-ethyl-2-methylcyclohexane.

Accepted Answer

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Quiz 3: An Introduction to Organic Compounds: Nomenclature, physical Properties, and Structure