Question

The IUPAC name of the given compound is

$C{H}_3-\underset{C{H}_3}{\underset{|}{C}}=CH-CHO$

• A. 3-Methyl-2-butenal
• B. 2-Methyl-2-butenal
• C. 2-Methyl-4-butenal
• D. 3-Methyl-3-butenal

Answer 1

The correct option is A

3-Methyl-2-butenal

The given compound contains an Aldehyde and is unsaturated (double bond). While numbering, the aldehyde group gets a higher preference and a lower number. So there is only one way to number the longest chain; it is to start from the functional group.


The double bond is between $C_2$ and $C_3$ while attached to it

Word root = but
Primary suffix = ene (double bond)
Secondary suffix = al
Secondary prefix = 3-methyl

Hence the IUPAC name is
3-methylbut -2-en-1-al or
(a) 3-methyl-2-butenal