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A conjugated diene is a compound with the alkene functional group of two 鈥渄ouble bonds or pie bonds鈥� (=), also known as alkadienes.

The conjugated diene is separated by one single bond, 鈥渁lternative position single and doublebond,鈥� and is more stable than isolated and cumulated diene due to its resonating structure.

The given allylic carbocation can be formed by three possible conjugated dienes, which are as follows:

• 3-methyl-2,4-hexadiene
• 4-methyl-1,3-hexadiene
• 2-Ethyl-1,3-pentadiene

The three conjugated dienes reacting with hydrogen halide (HBr) formed the given allylic carbocation, resonance stabilized, with the two resonating structures.

The two resonating structures of the given allylic carbocation reacting with bromine ion $\left({\text{Br}}^{\text{-}}\right)$formed the desired products 3-bromo-4-methyl-3-hexene and 4-bromo-4-methyl-2-hexene.

The structure of conjugated diene and the product formed is shown as follows:

Structure of diene and product