JEE Main 2025 Apr 8 Shift 2, Chemistry Q10: Introduction to Nomenclature

Step 1: Identify the Principal Functional Group

The –OH group is the principal functional group. Hence, it is named using the suffix “-ol”, not the prefix “hydroxy”.

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Step 2: Number the Ring

Numbering starts from the carbon bearing the –OH group so that it gets the lowest possible locant.

Choosing the direction that gives the double bond the lowest locant places the double bond between C2 and C3.

Hence, the parent compound is

$\boxed{\mathrm{Cyclopent}\text{-}2\text{-}\mathrm{en}\text{-}1\text{-}\mathrm{ol}}$

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Step 3: Locate the Substituent

With this numbering, the ethyl group is present at C4.

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Conclusion

Therefore, the correct IUPAC name is

$\boxed{4\text{-}\mathrm{Ethylcyclopent}\text{-}2\text{-}\mathrm{en}\text{-}1\text{-}\mathrm{ol}}$

$\boxed{\text{Correct Answer: Option (4)}}$