Question

In an SN1 mechanism, you've learned that the rate limiting step is the formation of the carbocation. The carbocation is unstable and will quickly react with any nucleophile that is present. In this experiment, you have both chloride and bromide ions competing as nucleophiles. If this reaction occurs via an SN1 mechanism and you added equal stoicheometric amounts of each ion you:

a) would predict more of the alkyl bromide product because bromide is a better nucleophile.
b) would not be able to predict the product ratio.
c) would predict more of the alkyl chloride product because chloride is a better nucleophile.
d) would expect equal amounts of alkyl bromide and alkyl chloride product.

Answer 1

In an SN1 reaction with equal amounts of chloride and bromide ions, more of the alkyl bromide product would be formed because bromide ions are better nucleophiles compared to chloride ions.

Step-by-step explanation:

In an SN1 mechanism, the formation of a carbocation is the rate-limiting step. This carbocation is unstable and reacts quickly with nucleophiles present in the reaction mixture. When chloride and bromide ions compete as nucleophiles and if equal stoichiometric amounts of each ion are added, the outcome depends on the nucleophilic strength of the ions.

Bromide ions are generally better nucleophiles than chloride ions due to their larger size and lower charge density, which allows them to form a transition state with the carbocation more easily. Therefore, the correct answer is:

a) would predict more of the alkyl bromide product because bromide is a better nucleophile.

Bromide's superior nucleophilic character means it will more readily attack the carbocation intermediate formed during the reaction, leading to a higher proportion of the alkyl bromide product compared to alkyl chloride when competing under similar conditions.