Two mole of an ester (A) are condensed in presence of sodium ethoxide to give a `beta-`keto ester (B) and ethanol. On heating in an acidic solution (B) gives ethanol and `beta-`keto acid (C). On decarboxylation (C) give 3-pentanone.
Identify (A),(B) and (C).

Answer

To solve the problem step by step, let's identify the compounds A, B, and C based on the provided information.

### Step 1: Identify Compound A
The question states that two moles of an ester (A) are condensed in the presence of sodium ethoxide. The general structure of an ester can be represented as RCOOR', where R and R' are alkyl groups. Given that the byproduct is ethanol (C2H5OH), we can deduce that one of the alkyl groups (R') in the ester must be ethyl (C2H5).

Assuming R is a methyl group (CH3), the structure of ester A can be represented as:
- **A: Ethyl acetate (CH3COOCH2CH3)**

### Step 2: Condensation Reaction to Form Compound B
The condensation of two moles of ester A in the presence of sodium ethoxide leads to the formation of a beta-keto ester (B) and ethanol. This is a type of aldol condensation.

The reaction can be summarized as follows:
1. The sodium ethoxide abstracts an alpha hydrogen from one ester molecule, forming a nucleophile.
2. This nucleophile then attacks the carbonyl carbon of another ester molecule, leading to the formation of a beta-keto ester.

The structure of beta-keto ester B can be represented as:
- **B: 3-oxobutanoate (CH3C(=O)C(=O)OCH2CH3)**

### Step 3: Heating Compound B to Form Compound C
When compound B is heated in an acidic solution, it yields ethanol and a beta-keto acid (C). The reaction involves the hydrolysis of the beta-keto ester, resulting in the formation of a beta-keto acid.

The structure of beta-keto acid C can be represented as:
- **C: 3-oxobutanoic acid (CH3C(=O)C(=O)OH)**

### Step 4: Decarboxylation of Compound C
The final step involves the decarboxylation of compound C, which results in the formation of 3-pentanone. Decarboxylation involves the removal of a carbon dioxide molecule (CO2) from the beta-keto acid.

The structure of 3-pentanone can be represented as:
- **3-pentanone: CH3C(=O)CH2CH2CH3**

### Summary of Compounds
- **A:** Ethyl acetate (CH3COOCH2CH3)
- **B:** 3-oxobutanoate (CH3C(=O)C(=O)OCH2CH3)
- **C:** 3-oxobutanoic acid (CH3C(=O)C(=O)OH)