Question

Which of the following is the correct IUPAC name of the given organic compound (X)?
The structure of compound $ X $ is as follows:

$ \text{H}_3\text{C} - \text{CH}_3 - \text{CH} = \text{CH} - \text{H} - \text{Br} $

• A. 2-Bromo-2-methylbut-2-ene
• B. 3-Bromo-3-methylprop-2-ene
• C. 1-Bromo-2-methylbut-2-ene
• D. 4-Bromo-3-methylbut-2-ene

Hint:

When naming organic compounds, always prioritize giving the lowest possible number to the position of the double bond and substituents. If there are multiple substituents, assign the lowest possible sum of numbers.

Answer 1

The Correct Option is C

Step 1: Determine the parent chain.
The longest continuous carbon chain containing the double bond has four carbons, establishing "butene" as the base name for this alkene.
Step 2: Number the parent chain.
Number the chain to give the double bond the lowest possible locant. The double bond is positioned between carbons 2 and 3, resulting in the numbering scheme: \[ \text{H}_3\text{C} - \text{CH}_3 - \text{CH} = \text{CH} - \text{H} - \text{Br} \] This assigns the double bond to position 2, making the parent name "but-2-ene."
Step 3: Identify substituents.
A methyl group (CH₃) is attached to carbon 2.
A bromine atom (Br) is attached to carbon 1.
Step 4: Assign locants to substituents.
The methyl group is at position 2, and the bromo group is at position 1. The lowest possible locants are assigned as follows:
Methyl group: carbon 2
Bromo group: carbon 1
Step 5: Assemble the IUPAC name.
The IUPAC name is derived by combining the substituent names and positions with the parent chain name: 1-Bromo-2-methylbut-2-ene.
"But" signifies the four-carbon chain.
"2-ene" indicates the double bond starts at carbon 2.
"2-methyl" denotes a methyl group on carbon 2.
"1-bromo" indicates a bromine atom on carbon 1.
Therefore, the systematic name is 1-Bromo-2-methylbut-2-ene.