What is the IUPAC name of the following compound?

1-Bromo-2-methylbut-2-ene

The correct answer is Option (1) → 1-Bromo-2-methylbut-2-ene

To determine the IUPAC name, follow the standard steps:

1. Select the longest carbon chain containing the double bond.

2. Number the chain so that the double bond gets the lowest possible number.

3. Identify and number substituents.

Step 1: Identify the longest chain

From the structure, the longest chain containing the double bond has $\textbf{four carbon atoms}$.

Parent chain = $\textbf{butene}$

Step 2: Number the chain

Numbering is done from the end that gives the $\textbf{double bond the lowest locant}$.

Thus the double bond lies between $\textbf{C-2 and C-3}$.

Parent name:

$\textbf{but-2-ene}$

Step 3: Identify substituents

Substituents present:

• $ \textbf{Bromo group (Br)}$ attached to carbon $\textbf{1}$
• Methyl group ($CH_3$) attached to carbon $\textbf{2}$

Step 4: Write the complete IUPAC name

Substituents are written alphabetically.

Thus the name becomes:

1-Bromo-2-methylbut-2-ene