The number of possible isomers of butene are:

• (A) 3
• (B) 2
• (C) 4
• (D) 5

To determine the number of possible isomers of butene, we first need to understand what butene is. Butene is an alkene with the molecular formula C4H8, and it can exist in different structural forms due to the presence of a double bond. The isomers can be categorized into structural isomers and geometric isomers. Let's break this down step by step.

Types of Isomers

Isomers are compounds that have the same molecular formula but different structural arrangements. In the case of butene, we can identify two main types:

• Structural Isomers: These differ in the connectivity of atoms.
• Geometric Isomers: These arise due to the restricted rotation around the double bond, leading to different spatial arrangements.

Identifying Structural Isomers of Butene

For butene, we can have the following structural isomers:

• 1-Butene: The double bond is between the first and second carbon atoms.
• 2-Butene: The double bond is between the second and third carbon atoms. This can exist in two forms:
• Cis-2-butene: The two methyl groups (CH3) are on the same side of the double bond.
• Trans-2-butene: The two methyl groups are on opposite sides of the double bond.
• Isobutene (or 2-methylpropene): This is a branched isomer where the double bond is between the first and second carbon of a three-carbon chain with a methyl group attached.

Counting the Isomers

Now, let's summarize the isomers we identified:

• 1-Butene
• Cis-2-butene
• Trans-2-butene
• Isobutene (2-methylpropene)

In total, we have four distinct isomers of butene. Therefore, the correct answer to the question regarding the number of possible isomers of butene is:

Final Answer

(C) 4

Understanding these isomers is crucial in organic chemistry, as the different structures can lead to varying chemical properties and reactivities. This concept is foundational for further studies in organic compounds and their behaviors in reactions.