cis-1,2-diethylcyclopropane has a larger heat of combustion than that of the trans isomer. Determine the more stable isomer. Explain your answer using drawings.

• A. The cis isomer is more stable because the eclipsed interactions between two ethyl groups stabilize the molecule.
• B. The trans isomer is more stable because the eclipsed interactions between two ethyl groups stabilize the molecule.
• C. The cis isomer is more stable because the eclipsed interactions between ethyl groups and hydrogens are more favorable than eclipsed interactions between ethyl groups
• D. The trans isomer is more stable because the eclipsed interactions between ethyl groups and hydrogens are more favorable than eclipsed interactions between ethyl groups

Answer: (D)