Identify 'A' and 'B' :

Question

Accepted Answer

Option 1 is the correct answer, where $A = CH_3CHO$ (acetaldehyde) and $B = CH_3COOH$ (acetic acid). Here's a detailed explanation justifying why this option is correct and why the others are not:

1. **Explanation for Option 1:**
   - **$A = CH_3CHO$ (Acetaldehyde):** Acetaldehyde is a simple aldehyde with the formula CH₃CHO. It is a common intermediate in the oxidation of ethanol and is known for its role in various chemical reactions, including its conversion to acetic acid.
   - **$B = CH_3COOH$ (Acetic Acid):** Acetic acid is a carboxylic acid with the formula CH₃COOH. It is a well-known product of the oxidation of acetaldehyde. The conversion from acetaldehyde to acetic acid is a classic example of an oxidation reaction where the aldehyde group is oxidized to a carboxylic acid group.
   - The relationship between acetaldehyde and acetic acid is well-established in organic chemistry, making Option 1 the correct choice.

2. **Explanation for why other options are incorrect:**

- **Option 2: $A = CH_3COOH, \ B = CH_3CHO$**
     - This option suggests that acetic acid is converted to acetaldehyde, which is not a typical or straightforward reaction. Acetic acid is more oxidized than acetaldehyde, and converting a carboxylic acid to an aldehyde typically requires a reduction process, which is not as common or direct as the oxidation of an aldehyde to a carboxylic acid.

- **Option 3: $A = HCHO, \ B = CO_2$**
     - This option involves formaldehyde (HCHO) and carbon dioxide (CO₂). While formaldehyde can be oxidized to formic acid and further to carbon dioxide, the direct relationship between these two compounds is not as straightforward or relevant as the acetaldehyde to acetic acid conversion. Additionally, the question does not imply such a transformation.

- **Option 4: $A = CH_3CHO, \ B = CH_2=CH_2$**
     - This option suggests a relationship between acetaldehyde and ethylene (CH₂=CH₂). However, acetaldehyde is not typically converted to ethylene in standard chemical processes. Ethylene is an alkene, and its formation from acetaldehyde would require a different set of reactions, such as dehydration, which is not as direct or relevant as the oxidation to acetic acid.

In conclusion, Option 1 is the correct answer because it accurately represents the well-known chemical relationship between acetaldehyde and acetic acid through an oxidation process. The other options do not reflect such a direct or typical chemical transformation.