IUPAC name of the following compound is:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 4-Bromopent-2-ene
1. Choose the longest chain containing C=C
2. Give double bond lowest locant
3. Then number substituents
Step 1: Identify the longest chain containing the double bond
From the structure:
$CH_3-CH=C-CH(Br)-CH_3$
That is a 5-carbon chain pent.
Step 2: Number the chain
Rule: Double bond gets the lowest possible number.
Numbering from the left:
|
Carbon |
Group |
|
C1 |
$\text{CH}_3$ |
|
C2 |
C of double bond |
|
C3 |
C of double bond |
|
C4 |
$\text{CH(Br)}$ |
|
C5 |
$\text{CH}_3$ |
Double bond is between C2 and C3 $\rightarrow$ pent-2-ene.
If we numbered from right, double bond would be at 3 $\rightarrow$ not preferred.
Step 3: Position of substituent
Bromine is on carbon 4.
So name = 4-Bromopent-2-ene