Which is the correct IUPAC name of the compound, CH_3CH=CHC(Br) (CH_3…

The correct answer is Option (1) → 4-Bromo-4-methylpent-2-ene

In IUPAC naming of an alkene, the parent chain is the longest chain containing the double bond, and it is numbered from the end that gives the double bond the lowest locant. Substituents are then given their locants and written in alphabetical order (bromo before methyl).

Writing the compound out in full:

    \( \displaystyle \ce{CH3-CH=CH-C(Br)(CH3)-CH3} \)

The longest chain through the double bond has five carbons (pent-). Numbered from the left, the double bond starts at C2; from the right it would start at C3, so the left end is chosen: C1 is the left \( \ce{CH3} \), C2 and C3 carry the double bond, C4 is the carbon with Br and \( \ce{CH3} \), and C5 is the last \( \ce{CH3} \). C4 carries both the bromine atom and a methyl group. So the name is 4-bromo-4-methylpent-2-ene.