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

The intermediate formed during the addition of hydrogen halide (HX) to cyclohexene is a cyclohexyl carbocation. The reaction mechanism follows electrophilic addition, including nucleophilic attack by the alkene and the release of the halide ion (X-). The carbocation is an electron-deficient species with a positive charge on the carbon atom and is highly reactive. It is immediately attacked by the halide ion to form the final product, cyclohexyl halide.

Step-by-step solution

Write down the overall reaction

The overall reaction of the addition of a hydrogen halide (HX) to an alkene (cyclohexene) can be written as follows: Cyclohexene + HX → Cyclohexyl Halide Here, X is the halogen (such as Cl, Br or I).

Explain the reaction mechanism

The reaction mechanism for the addition of HX to cyclohexene follows the electrophilic addition mechanism. It occurs via a two-step process which involves the formation of a carbocation intermediate. The mechanism can be summarized as follows: 1. Alkene acts as a nucleophile (electron-rich species) and attacks the hydrogen in the HX molecule (electrophile) forming a new carbon-hydrogen bond. In the process, the H-X bond breaks, and the halide ion (X-) is released. 2. The halide ion then attacks the carbocation (resulting from the first step) forming a carbon-halogen bond, generating the final cyclohexyl halide.

Describe the intermediate that is thought to form

The intermediate that forms during the reaction is a carbocation. In the case of cyclohexene and hydrogen halide, the intermediate carbocation is cyclohexyl carbocation. The carbocation is an electron-deficient species, with a positive charge on the carbon atom, which is the site of electrophilic attack (carbon double bond) in cyclohexene. Here is the structure of the cyclohexyl carbocation intermediate: ``` H H H H \| | | | H--C--C--C--H |\_/_/ C H | H ``` This intermediate is highly reactive and is immediately attacked by the halide ion (X-) in the second step of the reaction. This results in the formation of the final product, cyclohexyl halide.