Compound (A) `(C_(6)H_(12)O_(2))` on reduction with `LiAlH_(4)` yielded two compounds (B) and (C ). The compound (B) on oxidation gave (D), which on treatment with aqueous alkail and subsequent heating furnished (E ). The latter on catalytic hydrogenation gave (C ). The compound (D) was oxidised further to give (F) which was found to be a monobasic acid (molecular formula weight `= 60.0`). Deduce the structures of (A), (B), (C ), (D), and (E ).

Answer

To deduce the structures of compounds A, B, C, D, and E based on the information provided, we will follow a systematic approach:

### Step-by-Step Solution:

1. **Identify Compound A (C6H12O2)**:
- Given the molecular formula C6H12O2, we can infer that it is likely an ester due to the presence of two oxygen atoms and the degree of unsaturation.
- A reasonable structure for compound A is ethyl hexanoate:
\[ CH_3(CH_2)_4C(=O)OCH_2CH_3 \]

2. **Reduction of Compound A with LiAlH4**:
- When compound A is reduced with lithium aluminum hydride (LiAlH4), it typically yields two alcohols (B and C).
- The reduction of the ester will produce:
- **B**: 1-hexanol \((CH_3(CH_2)_4CH_2OH)\)
- **C**: Ethanol \((CH_3CH_2OH)\)

3. **Oxidation of Compound B to Form Compound D**:
- Compound B (1-hexanol) undergoes mild oxidation to form an aldehyde.
- The oxidation of 1-hexanol yields:
- **D**: Hexanal \((CH_3(CH_2)_4CHO)\)

4. **Treatment of Compound D with Aqueous Alkali**:
- When compound D (hexanal) is treated with aqueous alkali and heated, it undergoes an aldol condensation to form an alkene.
- The major product (E) from this reaction will be:
- **E**: 2-hexene \((CH_3CH=CH(CH_2)CH_2CH_3)\)

5. **Catalytic Hydrogenation of Compound E**:
- The compound E (2-hexene) undergoes catalytic hydrogenation, which adds hydrogen across the double bond.
- This reaction regenerates compound C:
- **C**: 1-hexanol \((CH_3(CH_2)_4CH_2OH)\)

6. **Further Oxidation of Compound D to Form Compound F**:
- Compound D (hexanal) can be oxidized further to yield a carboxylic acid.
- The oxidation of hexanal gives:
- **F**: Hexanoic acid \((CH_3(CH_2)_4COOH)\)
- The molecular weight of hexanoic acid is 60 g/mol, confirming that it is a monobasic acid.

### Summary of Structures:
- **A**: Ethyl hexanoate \((CH_3(CH_2)_4C(=O)OCH_2CH_3)\)
- **B**: 1-Hexanol \((CH_3(CH_2)_4CH_2OH)\)
- **C**: Ethanol \((CH_3CH_2OH)\)
- **D**: Hexanal \((CH_3(CH_2)_4CHO)\)
- **E**: 2-Hexene \((CH_3CH=CH(CH_2)CH_2CH_3)\)
- **F**: Hexanoic acid \((CH_3(CH_2)_4COOH)\)