For the Cannizzaro reaction in which of the following statements is true regarding order and molecularity of the reaction ?

Options

A. `R=K [Ald]^(2)[OH^(-)]^(2)` , 4th order, bimolecular
B. `R=K [Ald]^(2)[OH^(-)]`, 3rd order, bimolecular
C. `R=K [Ald]^(2)[OH^(-)]^(2)`, 4th order, tetramolecular
D. `R=K[Ald]^(2)[OH^(-)]`, 3rd order, trimolecular

Answer

To solve the question regarding the Cannizzaro reaction and determine the true statements about the order and molecularity of the reaction, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Cannizzaro Reaction**:
- The Cannizzaro reaction occurs with aldehydes and ketones that lack alpha hydrogens. This reaction involves the disproportionation of aldehydes in the presence of a strong base, leading to the formation of an alcohol and a carboxylic acid.

2. **Identifying the Reaction Components**:
- For example, formaldehyde (HCHO) is a common aldehyde that can undergo the Cannizzaro reaction because it has no alpha hydrogen.

3. **Reaction Mechanism**:
- In a basic medium, the aldehyde reacts to form an intermediate. The mechanism involves nucleophilic attack by hydroxide ions (OH-) on the carbonyl carbon, leading to the formation of an alkoxide intermediate.

4. **Rate Law Determination**:
- The rate of the Cannizzaro reaction depends on the concentration of the aldehyde and the hydroxide ion. The rate law can be expressed as:
\[ \text{Rate} = k[\text{Aldehyde}]^2[\text{OH}^-] \]
- Here, \(k\) is the rate constant, and the concentrations of the aldehyde and hydroxide ions are included.

5. **Calculating Order of the Reaction**:
- The order of a reaction is the sum of the powers of the concentration terms in the rate law. In this case:
- The aldehyde concentration is raised to the power of 2.
- The hydroxide ion concentration is raised to the power of 1.
- Therefore, the total order of the reaction is:
\[ \text{Order} = 2 + 1 = 3 \]

6. **Determining Molecularity of the Reaction**:
- Molecularity refers to the number of reactant molecules involved in the rate-determining step of the reaction. In this case, two molecules of aldehyde and one hydroxide ion are involved in the reaction.
- Thus, the molecularity is classified as bimolecular (since two molecules are involved).

7. **Final Answer**:
- Based on the above analysis, the Cannizzaro reaction has an order of 3 and is bimolecular. Therefore, the correct statement regarding the order and molecularity of the reaction is:
- **Order: 3**
- **Molecularity: Bimolecular**

### Conclusion:
The answer to the question is option B: Order is 3, and molecularity is bimolecular.