In the Cannizzaro reaction given below
`2C_(6)H_(5)CHO overset(OH^(-))rarr C_(6)H_(5)CH_(2)OH+C_(6)H_(5)COO^(-)`
the slowest step is

Options

A. attack of `OH^(-)` at the carbonyl group.
B. transfer of hydride ion to the carbonyl group.
C. abstraction of proton from the carboxylic acid.
D. feprotonation of `C_(6)H_(5)CH_(2)OH`.

Explanation

To determine the slowest step in the Cannizzaro reaction, we need to analyze the reaction mechanism involved. The Cannizzaro reaction involves the disproportionation of non-enolizable aldehydes in the presence of a strong base, leading to the formation of an alcohol and a carboxylic acid salt.

### Step-by-Step Solution:

1. **Identify the Reactants and Products**:
The reaction given is:
\[ 2C_{6}H_{5}CHO \overset{OH^{-}}{\rightarrow} C_{6}H_{5}CH_{2}OH + C_{6}H_{5}COO^{-} \]
Here, benzaldehyde (C₆H₅CHO) is the reactant, and the products are benzyl alcohol (C₆H₅CH₂OH) and the benzoate ion (C₆H₅COO⁻).

2. **Mechanism Overview**:
The Cannizzaro reaction proceeds via nucleophilic attack by hydroxide ion (OH⁻) on the carbonyl carbon of the aldehyde. This leads to the formation of a tetrahedral intermediate.

3. **Formation of Tetrahedral Intermediate**:
The hydroxide ion attacks the carbonyl carbon, resulting in a tetrahedral intermediate where the carbonyl oxygen becomes negatively charged (alkoxide ion).

4. **Hydride Transfer**:
The next step involves the transfer of a hydride ion (H⁻) from the tetrahedral intermediate to another molecule of the aldehyde. This step is crucial as it leads to the formation of the alcohol and the carboxylate ion.

5. **Identify the Rate-Determining Step**:
In the Cannizzaro reaction, the hydride transfer is the slowest step. This is because it involves breaking a bond and forming a new one, which typically has a higher activation energy compared to other steps in the reaction mechanism.

6. **Conclusion**:
Therefore, the slowest step in the Cannizzaro reaction is the hydride transfer from the tetrahedral intermediate to the other aldehyde molecule.

### Final Answer:
The slowest step in the Cannizzaro reaction is the hydride transfer from the tetrahedral intermediate to the aldehyde.

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