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Nucelophilic aliphatic substitution reac...

Nucelophilic aliphatic substitution reaction is given by those compounds which have nucleophiic groups as leaving. Less is the basicity of the leaving group. More is its leaving power. Leaving group in the form of nucleophile (charged of neutral)
Leaving power of which grops is maximum ?
Leaving power of which group is maximum ?

A

`-O-underset(O) underset(||)overset(O) overset(||)S-CF_(3)`

B

`-overset(o+)N-=N`

C

`-O-underset(O) underset(||)overset(O) overset(||)S-CH_(3)`

D

`-overset(Theta)l`

Text Solution

AI Generated Solution

The correct Answer is:
To determine which leaving group has the maximum leaving power in nucleophilic aliphatic substitution reactions, we need to analyze the basicity and stability of the leaving groups. Here’s a step-by-step solution: ### Step 1: Understand Leaving Groups Leaving groups are atoms or groups that can depart from the parent molecule during a chemical reaction. Their ability to leave is influenced by their stability after departure. Generally, weaker bases are better leaving groups because they are more stable in their anionic or neutral forms. **Hint:** Remember that a good leaving group should be stable when it leaves the molecule. ### Step 2: Compare Basicity The basicity of leaving groups is inversely related to their leaving power. The less basic a group is, the better it is as a leaving group. For example, halides (like I⁻, Br⁻, Cl⁻) are better leaving groups than hydroxide (OH⁻) because hydroxide is a stronger base. **Hint:** Think about the strength of bases; the weaker the base, the better the leaving group. ### Step 3: Evaluate Specific Leaving Groups Let’s consider some common leaving groups: - **Iodide (I⁻)**: A good leaving group due to its low basicity and high stability as a neutral iodine atom. - **Bromide (Br⁻)**: Also a good leaving group, but not as good as iodide. - **Chloride (Cl⁻)**: A decent leaving group, but less effective than bromide and iodide. - **Fluoride (F⁻)**: A poor leaving group due to its high basicity. - **Sulfonate groups (like TsO⁻ or MsO⁻)**: These are excellent leaving groups due to their stability after leaving. **Hint:** Compare the stability of the leaving groups after they depart; more stable groups are better leaving groups. ### Step 4: Identify the Best Leaving Group Among the groups mentioned, the best leaving groups are typically the neutral species that can stabilize themselves after leaving. For example, the azide ion (N₂) is a very stable neutral species after leaving, making it an excellent leaving group. **Hint:** Look for neutral species that can stabilize themselves effectively after leaving. ### Conclusion In conclusion, the maximum leaving power is exhibited by the azide ion (N₂), which is neutral and highly stable after departure. Among the charged groups, iodide (I⁻) is the best leaving group due to its low basicity and stability as a neutral iodine atom. **Final Answer:** The leaving power of the azide ion (N₂) is maximum, followed by iodide (I⁻).
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