The number of structural isomers of pentane is

[amp_mcq option1=”5″ option2=”4″ option3=”2″ option4=”3″ correct=”option4″]

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UPSC NDA-2 – 2022

The correct answer is 3.

Structural isomers are compounds with the same molecular formula but different arrangements of atoms. Pentane has the molecular formula C₅H₁₂. The three structural isomers of pentane are:
1. n-pentane (a straight chain of five carbon atoms).
2. Isopentane (2-methylbutane, a four-carbon chain with a methyl group attached to the second carbon).
3. Neopentane (2,2-dimethylpropane, a three-carbon chain with two methyl groups attached to the central carbon).

As the number of carbon atoms increases in alkanes, the number of possible structural isomers grows rapidly. For example, hexane (C₆H₁₄) has 5 isomers, and heptane (C₇H₁₆) has 9 isomers.

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