The decreasing order of nucleophilicities of the following is :
(I) `H_2 O`
(II) `EtOH`
(III) `MeCOO^(Ө)`
(IV) `overset (Ө) O H`
(V) `EtO^(Ө)`.

Options

A. `(V) gt (IV) gt (III) gt (II) gt (I)`
B. `(I) gt (II) gt (III) gt (IV) gt (V)`
C. `(IV) gt (V) gt (III) gt (II) gt (I)`
D. `(I) gt (II) gt (III) gt (V) gt (IV)`

Explanation

To determine the decreasing order of nucleophilicities of the given compounds, we need to analyze their basicity, as nucleophilicity is often correlated with basicity. Here’s the step-by-step solution:

### Step 1: Identify the Compounds
The compounds given are:
1. \( H_2O \) (Water)
2. \( EtOH \) (Ethanol)
3. \( MeCOO^- \) (Acetate ion)
4. \( OH^- \) (Hydroxide ion)
5. \( EtO^- \) (Ethoxide ion)

### Step 2: Classify the Compounds
- **Anions**: \( MeCOO^- \), \( OH^- \), \( EtO^- \)
- **Neutral Molecules**: \( H_2O \), \( EtOH \)

### Step 3: Analyze the Anions
Among the anions:
- \( EtO^- \) (Ethoxide ion) is a strong base and thus a strong nucleophile due to its negative charge being localized on oxygen.
- \( OH^- \) (Hydroxide ion) is also a strong base but less nucleophilic than \( EtO^- \) because it is a smaller alkoxide.
- \( MeCOO^- \) (Acetate ion) has resonance stabilization, which delocalizes the negative charge, making it less nucleophilic compared to the other two anions.

### Step 4: Rank the Anions
From strongest to weakest nucleophilicity:
1. \( EtO^- \)
2. \( OH^- \)
3. \( MeCOO^- \)

### Step 5: Analyze the Neutral Molecules
Among the neutral molecules:
- \( H_2O \) is less nucleophilic than \( EtOH \) because ethanol has an ethyl group that can donate electron density, making it a better nucleophile.

### Step 6: Rank the Neutral Molecules
From strongest to weakest nucleophilicity:
1. \( EtOH \)
2. \( H_2O \)

### Step 7: Combine the Rankings
Now, combining the rankings from both anions and neutral molecules, we get the overall decreasing order of nucleophilicity:
1. \( EtO^- \) (Ethoxide ion)
2. \( OH^- \) (Hydroxide ion)
3. \( MeCOO^- \) (Acetate ion)
4. \( EtOH \) (Ethanol)
5. \( H_2O \) (Water)

### Final Order
Thus, the final decreasing order of nucleophilicities is:
\[ EtO^- > OH^- > MeCOO^- > EtOH > H_2O \]

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