Which type of isomerism is exhibited by but-2-ene?

But-2-ene exhibits geometric isomerism due to the presence of a double bond between the second and third carbon atoms in its structure. This double bond restricts the rotation of the carbon chain, leading to two distinct spatial arrangements of the substituents attached to the carbons involved in the double bond.

In but-2-ene, there are two possible geometric isomers: the cis isomer, where the two methyl groups (–CH₃) are on the same side of the double bond, and the trans isomer, where the methyl groups are on opposite sides. This distinction arises because of the priority of the groups attached to the double-bonded carbons and the inability to freely rotate around the double bond.

This type of isomerism is characterized by the different orientations of the same molecular formula. In contrast, structural isomerism involves compounds differing in the connectivity of atoms, enantiomerism pertains to non-superimposable mirror images, and functional group isomerism refers to isomers that have different functional groups. Thus, the identification of but-2-ene as exhibiting geometric isomerism highlights its specific structural feature related to the double bond.