Which of the following is/are examples of pseudo unimolecular reactions?

Options

A. `CH_(3)CO_(2)C_(2)H_(5)+H_(2)Ooverset(H^(o+))rarrCH_(3)CO_(2)H + C_(2)H_(5)OH`
B. `C_(12)H_(22)O_(11)+H_(2)Ooverset(H^(o+))rarrunderset(("Glucose"))(C_(6)H_(12)O_(6))+underset(("Fructose"))(C_(6)H_(12)O_(6))`
C. `CH_(3)COCl+H_(2)OrarrCH_(3)CO_(2)H+HCl`
D. `CH_(3)CO_(2)C_(2)H_(5)+H_(2)Ooverset(overset(ɵ)OH)rarrCH_(3)CO_(2)H+C_(2)H_(5)OH`

Answer

To determine which of the given reactions are examples of pseudo unimolecular reactions, we need to understand the definitions of molecularity and order of a reaction.

### Step-by-Step Solution:

1. **Definition of Pseudo Unimolecular Reactions**:
- A pseudo unimolecular reaction occurs when a reaction has a molecularity greater than 1 (typically 2) but behaves as if it is first-order due to one reactant being in large excess.

2. **Analyzing Each Option**:
- **Option 1: Hydrolysis of Ester in Acidic Medium**:
- In this reaction, an ester reacts with water in the presence of an acid. Water is present in excess, so its concentration remains relatively constant during the reaction. The rate of reaction depends primarily on the concentration of the ester.
- **Conclusion**: This is a pseudo unimolecular reaction (Order = 1, Molecularity = 2).

- **Option 2: Inversion of Sugar in Acidic Medium**:
- This reaction involves the conversion of cane sugar (sucrose) into its component monosaccharides in the presence of an acid. Again, water is in excess, making its concentration effectively constant.
- **Conclusion**: This is also a pseudo unimolecular reaction (Order = 1, Molecularity = 2).

- **Option 3: Hydrolysis of Acetyl Chloride**:
- In this reaction, acetyl chloride reacts with water. Water is in excess, and the rate of reaction depends on the concentration of acetyl chloride.
- **Conclusion**: This is a pseudo unimolecular reaction (Order = 1, Molecularity = 2).

- **Option 4: Hydrolysis of Ester in Alkaline Medium**:
- In this case, the hydrolysis of an ester in a basic medium does not involve water in excess in the same way as the previous examples. The reaction is bimolecular because both the ester and the hydroxide ions from the base are involved in the rate-determining step.
- **Conclusion**: This is not a pseudo unimolecular reaction (Order ≠ 1, Molecularity = 2).

3. **Final Answer**:
- The examples of pseudo unimolecular reactions are Options 1, 2, and 3.

### Summary of Results:
- **Pseudo Unimolecular Reactions**:
- Option 1: Hydrolysis of Ester in Acidic Medium
- Option 2: Inversion of Sugar in Acidic Medium
- Option 3: Hydrolysis of Acetyl Chloride
- **Not Pseudo Unimolecular**:
- Option 4: Hydrolysis of Ester in Alkaline Medium