Compare the reactivity of primary, secondary, and tertiary haloalkanes in nucleophilic substitution reactions.

In nucleophilic substitution reactions, the reactivity of haloalkanes depends on the degree of substitution of the carbon atom to which the halogen is attached.

1. Primary Haloalkanes: In primary haloalkanes, the carbon atom that carries the halogen atom is only attached to one other carbon atom. This makes it less sterically hindered, allowing the nucleophile to easily approach and react with the carbon atom. Therefore, primary haloalkanes are generally more reactive in nucleophilic substitution reactions.

2. Secondary Haloalkanes: In secondary haloalkanes, the carbon atom that carries the halogen atom is attached to two other carbon atoms. This increases the steric hindrance, making it more difficult for the nucleophile to approach and react with the carbon atom. Therefore, secondary haloalkanes are generally less reactive than primary haloalkanes in nucleophilic substitution reactions.

3. Tertiary Haloalkanes: In tertiary haloalkanes, the carbon atom that carries the halogen atom is attached to three other carbon atoms. This greatly increases the steric hindrance, making it very difficult for the nucleophile to approach and react with the carbon atom. Therefore, tertiary haloalkanes are generally the least reactive in nucleophilic substitution reactions.

However, it's important to note that this trend is true for SN2 reactions, where the reaction rate is influenced by steric hindrance. In SN1 reactions, tertiary haloalkanes are more reactive because the rate-determining step is the formation of a carbocation, which is more stable when more substituted.