Question

a) Write the geometrical isomers of 2-butene and also designate them as E / Z isomers

Answer 1

Geometrical isomers of 2-butene are cis-2-butene and it is Z Isomer and the other is trans-2-butene which is E Isomer.
Remember the one which looks like E is actually Z and one which looks like Z is actually E

Answer 2

Cis-2- butene in the form of Z isomer and Trans-2-butene in the form of E isomer. In the given compound 2-butene, methyl group can be attached on the same side or it can be attached on the different side. When methyl group is attached on the same side of 2-butene it becomes Cis-isomer whereas when methyl group is attached on the opposite or different side it becomes Trans-isomer. In this, Cis-isomer is in Z-geometry because it has high priority group on same side where as Trans- isomer is in E-geometry because it has high priority group on opposite side.