Question

Haloalkanes give nucleophilic substitution reactions while haloarenes give electrophilic substitution reactions.

Hint:

In haloalkanes, the reaction mechanism is nucleophilic substitution (SN1 or SN2), whereas in haloarenes, it is electrophilic substitution due to the nature of the bond and reactivity.

Answer 1

- Haloalkanes: Haloalkanes (R-X) undergo nucleophilic substitution reactions where the halide ion (X) is replaced by a nucleophile. The mechanism involves the attack of a nucleophile (such as OH\(^-\), Cl\(^-\), or Br\(^-\)) on the carbon bonded to the halogen. This happens due to the polar nature of the C-X bond where the carbon is partially positive, making it susceptible to attack by nucleophiles. The typical mechanism for haloalkanes is SN1 or SN2 depending on the substrate.
- Haloarenes: Haloarenes (C6H5-X) undergo electrophilic substitution reactions where the halide is replaced by an electrophile (like NO\(_2\), SO\(_3\), or Cl\(_2\)) on the aromatic ring. The halogen in haloarenes is relatively electron-withdrawing, making the aromatic ring less reactive towards nucleophiles. Instead, the ring undergoes electrophilic substitution where the halogen leaves as a halide ion (X\(^-\)) and the electrophile takes its place. The reaction often occurs under the influence of catalysts like AlCl\(_3\) or FeCl\(_3\).