Which of the following best describes the molecules of a sample of ethane gas at room temperature?

A) Almost all of the molecules are frozen or locked in the eclipsed conformation.
B) Almost all of the molecules are frozen or locked in the staggered conformation.
C) The molecules are rapidly interconverting between the eclipsed and staggered conformations, but at any one time slightly more of them are present in the eclipsed conformation.
D) The molecules are rapidly interconverting between the eclipsed and staggered conformations, but at any one time slightly more of them are present in the staggered conformation.

Question

Elizabeth Leiva · Accepted Answer

Final Answer : D, Explanation :  Ethane has a staggered and eclipsed conformation due to the rotation around its C-C single bond. At room temperature, the molecules have enough thermal energy to rotate rapidly and interconvert between the two conformations. However, the staggered conformation is more stable due to decreased steric hindrance, so at any one time slightly more of the ethane molecules will be present in the staggered conformation. Therefore, choice D is the best description.

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