Question

multiple choice 1 point which of the following is an example of a good leaving group in s_n1 reactions? oh^- nh_2^- ch_3^- i^- previous

Explanation:

Step1: Understand leaving group ability

In $S_{N}1$ reactions, a good leaving group is stable after leaving. Stability is related to the conjugate acid's strength. Stronger conjugate acid (weaker base) makes a better leaving group.

Step2: Analyze each option

• $\ce{OH^{-}}$: Conjugate acid $\ce{H2O}$, $pK_{a} = 15.7$.
• $\ce{NH_{2}^{-}}$: Conjugate acid $\ce{NH3}$, $pK_{a} = 36$.
• $\ce{CH_{3}^{-}}$: Conjugate acid $\ce{CH4}$, $pK_{a} \approx 50$.
• $\ce{I^{-}}$: Conjugate acid $\ce{HI}$, $pK_{a}=-10$.

Since $\ce{HI}$ is the strongest acid among these conjugate acids (lowest $pK_{a}$), $\ce{I^{-}}$ is the most stable after leaving (weakest base), so it is the best leaving group.

Answer:

$\ce{I^{-}}$