Question

The alkene that exhibits geometrical isomerism is:
A.propane
B.2-methylpropene
C.2-butene
D.2-methyl-2-butene

Answer 1

Hint: To answer this question, you should recall the concept of geometrical isomerism. Geometrical isomerism is defined as the type of stereoisomerism having the same molecular formula and same structure but differ in the relative arrangement of atoms.

Complete step by step solution:
We know that isomers are defined as the molecules with the same molecular formula but possess a different arrangement of the atoms in space or different connectivity of atoms. The phenomenon in which the molecules in which the atoms that form the isomers are connected differently is known as structural isomerism. The phenomenon in which the connectivity of atoms is the same in isomers but a different spatial arrangement is a stereoisomerism.
2-Butene can exist as cis and trans isomers because of the double bond that leads to the restricted rotation. The cis-isomer has the two methyl groups on the same side and the trans-isomer has the two methyl groups on opposite sides.
2-methyl propene and 2-methyl-2-butene contain a double bond but the groups attached to one of the C of the double bond are the same. Hence, all the geometric isomers of these respective compounds will be identical.

Hence, it can be concluded that the correct option is option C.

Note: Geometric isomerism is one of the forms of stereoisomerism. The key point in geometrical isomers is the restricted rotation of a bond present somewhere in a molecule. At the most basic level of organic chemistry, carbon-carbon double bond is one of the examples leading to a restricted rotation.