When benzaldehyde is oxidised to give benzoic acid then the oxidation state of carbon of aldehydic group is changed from

Options

A. `+2" to "+3`
B. `+1" to "+3`
C. Zero to +2
D. No change

Answer

To determine the change in oxidation state of the carbon in the aldehydic group of benzaldehyde when it is oxidized to benzoic acid, we can follow these steps:

### Step 1: Identify the structure of benzaldehyde
Benzaldehyde has the following structure:
- It consists of a benzene ring (C6H5) attached to a carbonyl group (C=O) with a hydrogen atom (H) attached to the carbonyl carbon.

### Step 2: Assign oxidation state to the carbon in benzaldehyde
- The carbon in the aldehyde group is bonded to one oxygen (double bond) and one hydrogen (single bond).
- To find the oxidation state (OS) of the carbon in the aldehyde group, we can use the formula:
\[ \text{OS} = \text{(number of bonds to more electronegative atoms)} - \text{(number of bonds to less electronegative atoms)} \]
- Here, the carbon is bonded to one oxygen (which has an electronegativity of -2) and one hydrogen (which has an electronegativity of +1).
- Let the oxidation state of carbon be \(X\):
\[ X + (-2) + (+1) = 0 \]
\[ X - 1 = 0 \implies X = +1 \]
- Therefore, the oxidation state of the carbon in benzaldehyde is +1.

### Step 3: Identify the structure of benzoic acid
Benzoic acid has the following structure:
- It consists of a benzene ring (C6H5) attached to a carboxylic acid group (COOH).

### Step 4: Assign oxidation state to the carbon in benzoic acid
- The carbon in the carboxylic acid group is bonded to two oxygen atoms (one with a double bond and one with a single bond) and one hydroxyl group (OH).
- Let the oxidation state of this carbon be \(Y\):
\[ Y + (-2) + (-1) = 0 \]
\[ Y - 3 = 0 \implies Y = +3 \]
- Therefore, the oxidation state of the carbon in benzoic acid is +3.

### Step 5: Determine the change in oxidation state
- The oxidation state of the carbon changes from +1 in benzaldehyde to +3 in benzoic acid.
- Thus, the change in oxidation state is from +1 to +3.

### Conclusion
The oxidation state of the carbon of the aldehydic group in benzaldehyde changes from +1 to +3 when it is oxidized to benzoic acid.