cis-2-butene
 

trans-2-butene
 

cyclohexene
While we did not discuss the conformation of
cyclohexene in class, note that it is still in a chair conformation,
but somewhat squashed down.

intermediate formed from the
reaction of Cl⁺ and ethene

intermediate formed from the
reaction of Cl⁺ and cyclopentene

s-trans-1,3-butadiene

s-cis-1,3-butadiene
Note that this structure is non-planar!