Draw all four products obtained when 2-ethyl-3-methyl-1,3-

Step 1 of 3

This problem tells us that when the compound 2-ethyl-3-methyl-1,3-cyclohexadiene is treated with HBr at room temperature, four products are formed. We're asked to draw the structure of these compounds and to show the mechanism of their formation. Recall that at 40°C, we would expect the reaction to be under thermodynamic control, which means 1,4-addition of the HBr across ilie alkenes. However, the 1,2-addition product can also be formed if the corresponding cation is especially stable, and if the reaction is held at room temperature - slightly below the 40°C necessary for strict thermodynamic control.

The mechanism of the reaction as follows:

If the top double bond attacks the HBr molecule, two possible carbocation structures are formed which are resonance structures of each other. The first action is a tertiary allylic carbocation, which is especially stable. It can be attacked by a bromide anion to form the first expected product. Conversely, the resonance structure of this cation can be attacked by bromide to form the 1,4-addition product.