JEE Chemistry 2024 Question with Solution

Given: The compound name is 4-Methylpent-2-enal.

Find: The correct structure among the given options.

Naming the Structure: The name “4-Methylpent-2-enal” provides the key structural features of the molecule. The “pent” indicates a five-carbon chain. “2-enal” indicates the presence of a double bond at the second carbon and an aldehyde group at the terminal position. The “4-methyl” substituent specifies a methyl group attached to the fourth carbon.

Construct the Structure Step-by-Step:

1. Step 1: Place a five-carbon chain.
2. Step 2: Insert a double bond between carbons 2 and 3.
3. Step 3: Attach an aldehyde group at the first carbon.
4. Step 4: Add a methyl group to the fourth carbon.

Verify Each Option: Only Option (4) matches this structure, with the correct placement of the double bond, aldehyde group, and methyl substituent.

Conclusion: The structure in Option (4) is correct for 4-Methylpent-2-enal. Therefore, the correct option is D.

Given: The compound name is 4-Methylpent-2-enal.

Find: Which option matches the IUPAC name.

To determine the structure of 4-Methylpent-2-enal, first identify each part of the name:

1. Determine the Parent Chain: The word pent indicates a five-carbon chain.
2. Locate the Functional Group: The suffix al signifies an aldehyde group at carbon 1.
3. Locate the Double Bond: The term 2-en indicates a double bond starting at carbon 2.
4. Identify the Substituent: The prefix 4-Methyl indicates a methyl group attached to carbon 4.

Thus, the required structure must contain:

• a five-carbon parent chain,
• a terminal aldehyde group,
• a double bond between carbon 2 and carbon 3,
• a methyl substituent on carbon 4.

Comparing the options on this basis, the solution identifies Option D as the matching structure.

Conclusion: The correct option is D.