Constitutional Isomers: Understanding the Molecular Structures

Which of the following is not a constitutional isomer of C₆H₁₂?

1-methylcyclopentane

hex-2-ene

cyclohexane

hex-3-yne

3-methyl-pent-1-ene

Final Answer: All the given options except cyclohexane are constitutional isomers of C₆H₁₂. Why?

Answer:

All the compounds mentioned are constitutional isomers of C₆H₁₂ except cyclohexane. Let's understand why.

The concept of constitutional isomers revolves around the molecular formula and the arrangement of atoms within a compound. In the case of C₆H₁₂, the listed options have different structures that meet the molecular formula except for cyclohexane.

1-methylcyclopentane is a cyclic hydrocarbon with a methyl group attached, making it a constitutional isomer of C₆H₁₂. Hex-2-ene and hex-3-yne are alkene and alkyne compounds, respectively, with different bonding patterns, which also qualify them as constitutional isomers of C₆H₁₂. 3-methyl-pent-1-ene consists of an alkene structure with a methyl group, fulfilling the criteria for a constitutional isomer.

However, cyclohexane stands out as it is a cyclic hydrocarbon without any double bonds or substituted groups, diverging from the required molecular structure of C₆H₁₂. Due to this unique arrangement, cyclohexane is not a constitutional isomer of C₆H₁₂.

Understanding the concept of constitutional isomers helps in grasping the diverse possibilities of molecular structures based on the same chemical formula. It showcases the intricate nature of organic chemistry and the varied arrangements atoms can form within compounds.