The correct order of the ability of the leaving group is

Options

A. `-OCOC_2H_5gt-OC_2H_5gt-OSO_2MegtOSO_2CF_3`
B. `-OC_2H_5gt-OCOC_2H5gtOSO_2CF_3-OSO_2Me`
C. `-OSO_2CF_3gt-OSO_2Me gt-OCOC_2H_5gt-OC_2H_5`
D. `_OCOC_2H_5gt-OSO_2CF_3gt-OC_2H_5gt-OSO_2Me`

Answer

To determine the correct order of the ability of the leaving group, we need to analyze the stability of the leaving groups based on the stability of the negative charge they carry. The more stable the negative charge, the better the leaving group will be. Here’s a step-by-step breakdown of the solution:

### Step 1: Identify the Leaving Groups
We need to identify the leaving groups we are comparing. In the transcript, the following groups are mentioned:
- O⁻ (alkoxide)
- CO (carbonyl)
- C2H5 (ethyl)
- SO (sulfide)
- CF3 (trifluoromethyl)

### Step 2: Analyze the Stability of Each Leaving Group
1. **O⁻ (alkoxide)**: The negative charge on oxygen is relatively stable due to its electronegativity, but it is not very stable when compared to other groups that can delocalize the charge.

2. **CO (carbonyl)**: The carbonyl group can stabilize the negative charge through resonance, making it a better leaving group than simple alkoxides.

3. **C2H5 (ethyl)**: This group does not stabilize the negative charge effectively, making it a poor leaving group.

4. **SO (sulfide)**: Sulfur can stabilize the negative charge better than oxygen due to its larger size and ability to disperse electron density.

5. **CF3 (trifluoromethyl)**: The CF3 group is highly electronegative and can stabilize the negative charge through inductive effects, making it a very good leaving group.

### Step 3: Compare the Groups
Now we can rank the groups based on the stability of the negative charge:
- **CF3**: Most stable due to strong -I effect.
- **SO**: Good stability due to size and charge dispersion.
- **CO**: Moderate stability due to resonance.
- **O⁻**: Less stable due to lack of resonance.
- **C2H5**: Least stable due to poor charge stabilization.

### Step 4: Conclusion
The order of leaving groups from best to worst is:
1. CF3
2. SO
3. CO
4. O⁻
5. C2H5

Thus, the correct order of the ability of the leaving group is CF3 > SO > CO > O⁻ > C2H5.