Question

But-2-ene can exhibit:
A. geometrical isomerism
B. structural isomerism
C. metamerism
D. tautomerism

Answer 1

Hint: Isomers are compounds that possess the same molecular formula but differ from each other in physical and chemical properties. Since isomers have the same molecular formula the difference in their properties might be due to different modes of combination of arrangement of atoms within the molecule.

Complete step by step solution:The isomers which differ only in the orientation of atoms in space are known as stereoisomers and this phenomenon is known as stereoisomerism. One of the types is geometrical isomerism, isomers which possess the same molecular and structural formula but differ in arrangement of atoms or groups in space around the double bonds are known as geometrical isomers and the phenomenon is known as geometrical isomerism.
Such isomers are not superimposable, that is if you try to put one compound over another. You will find discrepancy and hence they cannot be superimposed on each other.
Since the above compound (but-2-ene) has double bonds and is an alkene therefore is a geometrical isomer. Cis-trans isomerism is shown when similar groups are on the same side it is cis and if same groups are on the opposite side it is trans isomerism. Let us draw structure of but-2-ene exhibiting both cis-tans isomerism in geometrical isomerism.

In other words, stereoisomerism is exhibited by such compounds which have identical molecular structure but different configurations. The other isomers are structural isomers.
Hence we can conclude that the above hydrocarbon compound but-2-ene is a geometrical isomer.

Therefore the correct option is A.

Note: Certain differentiating properties for cis-trans isomerism is dipole moment, melting point etc. as per stability is concerned, generally trans-isomer is more stable than cis-isomer as in cis form there will be steric repulsion.