In the following groups:
(I) `-OAc`, (II) `-OMe`, (III) `-OSO_(2)Me`, (IV) `OSO_(2)CF_(3)` the order of leaving group ability is-

Options

A. `I gt II gt III gt IV`
B. `IV gt III gt I gt II`
C. `III gt II gt I gt IV`
D. `II gt III gt IV gt I`

Answer

To determine the order of leaving group ability for the groups given in the question, we will follow a systematic approach based on the relationship between acidity and basicity. Here’s the step-by-step solution:

### Step 1: Identify the Groups
The groups provided are:
1. (I) `-OAc` (Acetate)
2. (II) `-OMe` (Methoxide)
3. (III) `-OSO2Me` (Methanesulfonate)
4. (IV) `-OSO2CF3` (Trifluoromethanesulfonate)

### Step 2: Understand the Relationship Between Leaving Group Ability and Basicity
Leaving group ability is inversely proportional to basicity. This means that a weaker base is a better leaving group. Therefore, we need to establish the order of basicity for these groups.

### Step 3: Determine the Acidity of the Corresponding Acids
To find the basicity order, we can look at the acidity of the corresponding acids:
- For `-OAc`, the corresponding acid is acetic acid (CH3COOH).
- For `-OMe`, the corresponding acid is methanol (CH3OH).
- For `-OSO2Me`, the corresponding acid is methanesulfonic acid (CH3SO3H).
- For `-OSO2CF3`, the corresponding acid is trifluoromethanesulfonic acid (CF3SO3H).

### Step 4: Compare the Acidity
The order of acidity can be determined based on the stability of the conjugate bases:
1. **Trifluoromethanesulfonic acid (CF3SO3H)** - Most acidic due to the strong electronegative CF3 group.
2. **Methanesulfonic acid (CH3SO3H)** - Next most acidic due to the sulfonate group.
3. **Acetic acid (CH3COOH)** - Less acidic than the sulfonic acids but more acidic than alcohols.
4. **Methanol (CH3OH)** - Least acidic.

### Step 5: Establish the Basicity Order
Since basicity is inversely proportional to acidity, the order of basicity is:
1. Methanol (strongest base)
2. Acetic acid
3. Methanesulfonic acid
4. Trifluoromethanesulfonic acid (weakest base)

### Step 6: Determine the Leaving Group Ability
Now, we reverse the basicity order to find the leaving group ability:
1. **Trifluoromethanesulfonate (OSO2CF3)** - Best leaving group
2. **Methanesulfonate (OSO2Me)** - Good leaving group
3. **Acetate (OAc)** - Moderate leaving group
4. **Methoxide (OMe)** - Poor leaving group

### Final Order of Leaving Group Ability
Thus, the order of leaving group ability is:
**OSO2CF3 > OSO2Me > OAc > OMe**