The hydrolyiss of ester in alkaline medium is a

Options

A. First order reaction with molecularity `1`
B. Second order reaction with molecularity ` 2`
C. First order reaction with molecularity `2`
D. Second order reaction with molecularity `1`

Answer

To solve the question regarding the hydrolysis of an ester in an alkaline medium, we need to analyze the reaction step by step.

### Step-by-Step Solution:

1. **Understanding the Reaction**:
The hydrolysis of an ester in an alkaline medium is a reaction where the ester reacts with a base (alkaline medium) to produce a carboxylic acid salt and an alcohol. This process is commonly referred to as saponification.

2. **Identifying the Reactants**:
In this reaction, we have:
- Ester (RCOOR')
- Alkaline medium (e.g., NaOH)

3. **Writing the Reaction**:
The general reaction can be represented as:
\[ RCOOR' + NaOH \rightarrow RCOO^{-}Na^{+} + R'OH \]
Here, RCOO^-Na^+ is the salt of the carboxylic acid, and R'OH is the alcohol produced.

4. **Determining the Rate Law**:
The rate of the reaction depends on the concentrations of both the ester and the alkaline medium. Therefore, we can express the rate law as:
\[ \text{Rate} = k[\text{Ester}][\text{Alkali}] \]
where \( k \) is the rate constant.

5. **Calculating the Order of the Reaction**:
The order of the reaction is determined by the sum of the powers of the concentration terms in the rate law. In this case:
- The power of the ester concentration is 1.
- The power of the alkali concentration is also 1.
Thus, the overall order of the reaction is:
\[ \text{Order} = 1 + 1 = 2 \]

6. **Determining Molecularity**:
Molecularity refers to the number of reactant molecules involved in the rate-determining step of the reaction. In this case, one molecule of ester reacts with one molecule of alkali, leading to a molecularity of:
\[ \text{Molecularity} = 2 \]

7. **Conclusion**:
Since the reaction is second order with respect to the concentrations of the reactants and has a molecularity of 2, the correct answer to the question is:
**B: Second order reaction with molecularity 2.**