Which of the following `IUPAC` names is not correct?

Options

A. (1) `3`-Ethylpentane-`1,4`-diene
B. (2) `2`-Isopropylbut-`1`-ene
C. (3) `3`-Methylenecyclopentene
D. (4) `4`-Allyl-`3`-propenylcyclohexa-`1,3`-diene

Answer

B

Explanation

First draw the structure corresponding to the given name. Then rename it according to the prescribed `IUPAC` rules to notice any possible error. In compound `(2)`, we have the possibility of another parent chain with more substituents:
`overset(4)(CH_(3))-underset("2-Ethyl-3-Methylbut-1-ene")(underset(CH_(3))underset(|)overset(3)(CH)-underset(CH_(2))underset(1||)overset(2)(C)-CH_(2)-CH_(3))`
(1)`{:(CH_(2)=CH-overset(3)(C)H-overset(4)(C)H=overset(5)(C)H_(2)),(" "|),(" "underset(2)(C)H=underset(1)(C)H_(2)):}`
(3)
(4)