Question: are cis-2-butene and trans-2-butene conformational isomers?
Answer: In principle, cis- and trans-2-butene are conformational isomers; in theory, they could be interconverted by a simple rotation about the central double bond. ... This time there is no imaginable rotation about bonds that can equilibrate the two isomers, so these two molecules are not conformational isomers.