Question

a dehydration reaction produces water as a byproduct. water is a good nucleophile that could react with the carbocation intermediate. why is that not a concern in this experiment?

Answer 1

Water acting as a nucleophile is not a concern in this dehydration reaction because the reaction conditions favor the addition of water to the carbocation intermediate, resulting in the formation of an alcohol.

Step-by-step explanation:

In a dehydration reaction, water is produced as a byproduct. Although water is a good nucleophile, it is not a concern in this experiment because the reaction conditions favor the addition of water to the carbocation intermediate, rather than water acting as a nucleophile.

The presence of a catalyst, such as sulfuric acid, promotes the hydration of the alkene by adding a water molecule across the C=C bond, resulting in the formation of an alcohol. This reaction occurs through electrophilic addition, where the electrophile is the carbocation formed during the reaction.

Answer 2

Water's reactivity as a nucleophile is not a major concern in a dehydration reaction due to the use of acid catalysts with poor nucleophile conjugate bases, high water concentration favoring formation rather than reactivity, and reaction conditions that favor elimination over nucleophilic addition.

Step-by-step explanation:

In a dehydration experiment involving alcohols, water is produced as a byproduct when an alcohol undergoes dehydration in the presence of a catalyst to form an alkene. The concern that water might act as a nucleophile and react with the carbocation intermediate can be addressed understanding the reaction conditions. Although water is a potential nucleophile, its reactivity is not a major concern in the dehydration reaction for several reasons.

Firstly, the experiment utilizes a strong acid like sulfuric acid, which has a conjugate base (HSO4-) that is a poor nucleophile. This decreases the likelihood of side reactions involving the conjugate base. Secondly, in a dehydration reaction, the formation of water is favored under the reaction conditions. Water being in higher concentration does play a role in the reaction's kinetics, but it doesn't lead to backward hydration under typical experimental conditions. Lastly, the reaction conditions are designed to favor the elimination reaction over any potential nucleophilic addition of water. The resulting alkene is often the most stable product, and the reaction is typically pushed to completion, minimizing the potential reverse reaction.