Question

Describe the intermediate that is thought to form in the addition of a hydrogen halide to an alkene, using cyclohexene as the alkene in your description.

Short answer

In the addition of a hydrogen halide (HX) to cyclohexene, the initial intermediate formed is a secondary carbocation after the protonation of the alkene's double bond by the hydrogen halide. The structure of this intermediate contains a positively charged carbon connected to two other carbons.

Step-by-step solution

Writing the initial reactants

Write down the given alkene (cyclohexene) and a generic hydrogen halide (HX), where X is a halide (like Cl, Br, I). Cyclohexene: \(C_6H_{10}\) Hydrogen halide: HX

Protonation of the alkene

The first step in the reaction of an alkene with a hydrogen halide is the protonation of the double bond. The electron-rich double bond in the alkene (cyclohexene) will attract the proton from the hydrogen halide (HX) to form a carbocation. Cyclohexene + HX → Carbocation + X^-

Identifying the carbocation

After the protonation of the alkene, a carbocation is formed. In the case of cyclohexene, the resulting carbocation will be a secondary carbocation since the positively charged carbon would be connected to two other carbons.

Writing the structure of the carbocation

Draw the structure of the secondary carbocation that forms: The carbocation: ``` H H H | | | H--C--C--+ | | | H H H ``` Remember that the "+" in the structure represents the positively charged carbon atom.

Final description

In the addition of a hydrogen halide (HX) to cyclohexene, the initial intermediate that forms is a secondary carbocation. This carbocation is formed after the protonation of the double bond in the alkene by the hydrogen halide. The structure of this intermediate contains a positively charged carbon, which is connected to two other carbons.