4. Alkanes and Cycloalkanes

Choose the conformation in each pair that is most stable. If both are equally stable, then write 'no difference.'

(a)

Which of the following cycloalkanes has the most angle strain?

Cyclopropane (C₃H₆, a three-membered ring) is more reactive than most other cycloalkanes.

c. Suggest why cyclopropane is so reactive.

Verify the strain energy shown in Table 3.8 for cycloheptane

Which conformation in each of the following pairs has the least strain energy?

(a)

The heat of combustion of cis-1,2-dimethylcyclopropane is larger than that of the trans isomer. Which isomer is more stable? Use drawings to explain this difference in stability.

The normal C(sp³)–C(sp³) bond length is 1.54 Å. The normal bond angle for an sp³-hybridized carbon is 109.5°. The following molecule experiences large deviations from these normal values. Explain these deviations. [Molecular models would be helpful here.]

Which conformation in each of the following pairs has the least strain energy?

(b)