The hydrolysis of which of the following takes the longest time ?

Options

A. `CH_(3) COCl`
B. `(CH_(3)CO)_(2)O`
C. `CH_(3)COOC_(2)H_(5)`
D. `CH_(3)CONH_(2)`

Answer

To determine which compound undergoes hydrolysis the slowest, we need to analyze the hydrolysis rates of the given compounds based on the groups attached to the carbonyl carbon. Let's break down the solution step by step:

### Step-by-Step Solution:

1. **Identify the Compounds**:
The compounds given are:
- A: \( \text{CS}_3\text{C} = \text{OCl} \)
- B: \( \text{CS}_3\text{C} = \text{OOC} = \text{OCS}_3 \)
- C: \( \text{CS}_3\text{C} = \text{OOC}_2\text{H}_5 \)
- D: \( \text{CS}_3\text{C} = \text{ONH}_2 \)

2. **Understand Hydrolysis**:
Hydrolysis involves the reaction of a compound with water, leading to the breakdown of the compound. The rate of hydrolysis can be influenced by the nature of the substituents attached to the carbonyl carbon.

3. **Analyze the Electron-Withdrawing and Electron-Donating Effects**:
- **Chlorine (Cl)** in compound A is an electron-withdrawing group, which increases the electrophilicity of the carbonyl carbon, making it more susceptible to nucleophilic attack.
- **OCOCS3** in compound B is also an electron-withdrawing group due to the presence of the carbonyl oxygen, but it has a more complex structure that can stabilize the carbonyl.
- **OC2H5** in compound C has a less electron-withdrawing effect compared to Cl and OCOCS3, making it less electrophilic.
- **NH2** in compound D is an electron-donating group, which decreases the electrophilicity of the carbonyl carbon, making it the least reactive towards hydrolysis.

4. **Order of Ease of Hydrolysis**:
Based on the analysis of the groups:
- Compound A (CS3C=OCl) will hydrolyze the fastest due to the strong electron-withdrawing effect of Cl.
- Compound B (CS3C=OOC=OCS3) will hydrolyze next, as it has an electron-withdrawing effect but is stabilized by resonance.
- Compound C (CS3C=OOC2H5) will hydrolyze slower than B due to the less electron-withdrawing effect of OC2H5.
- Compound D (CS3C=ONH2) will hydrolyze the slowest because NH2 is electron-donating, making the carbonyl carbon less electrophilic.

5. **Conclusion**:
The compound that takes the longest time to hydrolyze is **D: \( \text{CS}_3\text{C} = \text{ONH}_2 \)**.

### Final Answer:
The compound that undergoes hydrolysis the slowest is \( \text{CS}_3\text{C} = \text{ONH}_2 \) (Option D).