Which of the following conjugated dienes represent two conformations?

Question

Quizplus · Accepted Answer

Conjugated dienes I and II have a fixed conformation with a linear arrangement of atoms, whereas diene III has a flexible conformation with a bent arrangement of atoms. Conformational isomers occur when the molecules differ in the arrangement of atoms due to the rotation of a single bond. Therefore, I and II cannot have different conformations, while III can have different conformations due to the rotation around the single bond connecting the two methyl groups. Thus, only II and III represent two conformations.

Which of the Following Conjugated Dienes Represent Two Conformations