Which of the following conjugated dienes represent two conformations?
A)Only I and II
B)Only I and III
C)Only II and III
D)None of the choices

Question

Which of the following conjugated dienes represent two conformations? 
A)Only I and II 
B)Only I and III 
C)Only II and III 
D)None of the choices

Quizplus · Accepted Answer

Conjugated dienes are molecules with alternating single and double bonds. In the given structures, only structures II and III have alternating single and double bonds. Structure I has two double bonds next to each other which is not a conjugated diene. 
Structure II can exist in two conformations, cis and trans because there is a pi bond restricting rotation around the single bond. 
Structure III can also exist in two conformations, s-cis and s-trans, due to the same pi bond restriction.

Which of the Following Conjugated Dienes Represent Two Conformations