Interpret the IUPAC name: 4-Methylpent-2-enal

Let us break the name into parts:

• pent $\Rightarrow$ main chain has 5 carbons
• enal $\Rightarrow$ aldehyde group $(-CHO)$ is present, and it is carbon 1
• 2-en $\Rightarrow$ double bond is between carbon 2 and carbon 3
• 4-methyl $\Rightarrow$ a methyl group is attached to carbon 4

Write the parent chain numbering

Since aldehyde carbon is always carbon 1:

$\text{C1} - \text{C2} = \text{C3} - \text{C4} - \text{C5}$

with $\text{C1} = -CHO$

Add the substituent at carbon 4

A methyl group at carbon 4 gives:

$\text{CHO} - \text{CH}=\text{CH} - \text{CH}(CH_3) - \text{CH}_3$

Write the condensed structure clearly

The structure is:

$OHC-CH=CH-CH(CH_3)-CH_3$

or equivalently,

$CH_3-CH(CH_3)-CH=CH-CHO$

Match with the options

The correct option must represent:

$CH_3-CH(CH_3)-CH=CH-CHO$

This corresponds to Option C.

Comparison with stored answer

Stored correct answer = C

Derived answer = C

Hence, they agree.