Structure of 4-Methylpent-2-enal is :

Solution

Chemistry ma’am · 3 steps

The aldehyde carbon is always C1, so number every option from the CHO end and read off the name.

1. Decode the name. -al means the CHO carbon is C1. pent means a five-carbon chain, 2-en puts the double bond between C2 and C3, and 4-methyl puts a CH₃ branch on C4.
2. Target structure. Putting that together gives OHC-CH=CH-CH(CH₃)-CH₃. Now number each option from its CHO carbon and compare it with this.

   Option	Double bond	Methyl on	Correct name
   (a)	C4 = C5	C3	3-methylpent-4-enal
   (b)	C2 = C3	C3	3-methylpent-2-enal
   (c)	C2 = C3	C4	4-methylpent-2-enal
   (d)	C2 = C3	C2	2-methylpent-2-enal

3. So. Only (c), CH₃-CH(CH₃)-CH=CH-CHO, has the double bond at C2 and the methyl at C4. It is 4-methylpent-2-enal.

The idea to keep. In an aldehyde the CHO carbon is C1, every time. Fix C1 first, then place the double bond and the branches by counting from there.

Answer from the NTA final answer key. Solution by PrepWiser.