What is the correct IUPAC name of 

To determine the correct IUPAC name of the given cyclic compound, we apply the standard IUPAC nomenclature rules by identifying the principal functional group and assigning the appropriate numbering.

The molecule contains both a hydroxyl group $$(-OH)$$ and a carbon-carbon double bond $$\left(C=C\right)$$ in a five-membered ring. According to IUPAC priority rules, the hydroxyl group has higher priority than the double bond. Therefore, the suffix of the compound is “-ol”, and the carbon bearing the $$-OH$$ group is assigned position 1.

After fixing the hydroxyl-bearing carbon as carbon 1, the ring is numbered in the direction that gives the double bond the lowest possible locant. With this numbering, the double bond begins at carbon 2, and the ethyl substituent is located at carbon 4.

Thus, the numbering is:

• Hydroxyl group at C1
• Double bond between C2 and C3
• Ethyl substituent at C4

The name is constructed as follows:

• Substituent: 4-ethyl
• Parent ring: cyclopent
• Double bond: 2-en
• Principal suffix: 1-ol

Hence, the correct IUPAC name of the compound is

4-ethylcyclopent-2-en-1-ol.