Five isomeric para-disubsituted atomatic compounds `(A)` to `( E)` with molecular formula `C_(8) H_(8) O_(2)` were given for identification. Based on the following observations give structures of the compounds.
(i) Both `(A)` and `(B)` form silver mirror with Tollens reagent. Further, `(B)` gives a positive test with `FeCl_(3)` solution.
(ii) `(C)` gives positive iodoform test.
(iii) `(D)` is readily extracted in aqueous `NaHCO_(3)` solution.
(iv) `(E )` on acid hydrolysis gives `1,4-`dihydroxy benzene.

Answer

To solve the problem of identifying the five isomeric para-disubstituted aromatic compounds `(A)` to `(E)` with the molecular formula `C8H8O2`, we will analyze the observations given step by step.

### Step 1: Analyzing Compounds A and B
**Observation:** Both `(A)` and `(B)` form a silver mirror with Tollens' reagent. Further, `(B)` gives a positive test with `FeCl3` solution.

**Analysis:**
- The ability to form a silver mirror indicates that both `(A)` and `(B)` contain an aldehyde group (`-CHO`).
- The positive test with `FeCl3` suggests that compound `(B)` contains a phenolic group (`-OH` attached to a benzene ring).

**Structure of Compound A:**
- Since `(A)` is an aldehyde and is para-disubstituted, it could be **p-methylbenzaldehyde** (p-tolualdehyde).

**Structure of Compound B:**
- Compound `(B)` must have both the aldehyde and phenolic group. A suitable structure could be **p-hydroxybenzaldehyde** (also known as p-hydroxy-toluene).

### Step 2: Analyzing Compound C
**Observation:** `(C)` gives a positive iodoform test.

**Analysis:**
- The iodoform test indicates the presence of a methyl ketone or a secondary alcohol adjacent to a methyl group.
- A suitable structure for `(C)` could be **p-methylacetophenone**.

### Step 3: Analyzing Compound D
**Observation:** `(D)` is readily extracted in aqueous `NaHCO3` solution.

**Analysis:**
- This suggests that compound `(D)` contains a carboxylic acid group (`-COOH`), as carboxylic acids are soluble in sodium bicarbonate.
- A suitable structure for `(D)` could be **p-toluic acid**.

### Step 4: Analyzing Compound E
**Observation:** `(E)` on acid hydrolysis gives `1,4-dihydroxybenzene`.

**Analysis:**
- The hydrolysis yielding `1,4-dihydroxybenzene` (also known as hydroquinone) suggests that `(E)` is an ester that, upon hydrolysis, produces this compound.
- A suitable structure for `(E)` could be **p-methoxybenzoate**.

### Summary of Structures
- **Compound A:** p-Methylbenzaldehyde (p-tolualdehyde)
- **Compound B:** p-Hydroxybenzaldehyde
- **Compound C:** p-Methylacetophenone
- **Compound D:** p-Toluic acid
- **Compound E:** p-Methoxybenzoate