In an \( \text{S}_\text{N}2 \) substitution reaction of the type \( \text{R} - \text{Br} + \text{Cl}^- \xrightarrow{\text{DMF}} \text{R} - \text{Cl} + \text{Br}^- \), which one of the following has the highest relative rate?
Show Hint
In \( \text{S}_\text{N}2 \) reactions, less steric hindrance around the leaving group leads to a faster reaction rate.