An organic compound (A) `(C_(6)H_(10)O)` on reaction with `CH_(3)MgBr` followed by acid treatment gives compound (B). The compound (B) on ozonolysis gives compound (C ), which in the presence of a base gives 1-acetyl cyclopentene (D). The compound (B) on reaction with HBr gives compound (E ). Write the structures of (A), (B), (C ), (D), and (E ). Show how (D) is formed from (C ).

Answer

To solve the problem, we need to identify the structures of compounds (A), (B), (C), (D), and (E) based on the provided reactions and transformations. Let's break it down step by step.

### Step 1: Identify Compound (A)
Given that compound (A) has the molecular formula \(C_6H_{10}O\), we can calculate the double bond equivalence (DBE):

\[ \text{DBE} = \frac{(n - m + q)}{2} \]
where \(n\) is the number of carbon atoms, \(m\) is the number of hydrogen atoms, and \(q\) is the number of nitrogen atoms (which is zero here).

\[ \text{DBE} = \frac{(6 - 10 + 0)}{2} = \frac{-4}{2} = -2 \]

Since the DBE is 2, this suggests the presence of either two double bonds or one ring and one double bond. Given the presence of an oxygen atom, it is likely that compound (A) is a cyclic compound with a carbonyl group.

A suitable structure for compound (A) could be **cyclohexanone** (a six-membered ring with a ketone functional group).

### Step 2: Reaction of (A) with Grignard Reagent
When compound (A) reacts with \(CH_3MgBr\) (a Grignard reagent), it will add to the carbonyl carbon, forming an alcohol after acid treatment. The product (B) will be:

\[ \text{B} = \text{C}_6\text{H}_{12}\text{O}_2 \quad (\text{a secondary alcohol}) \]

The structure of compound (B) can be represented as **2-methyl-2-pentanol**.

### Step 3: Ozonolysis of Compound (B)
The ozonolysis of compound (B) will cleave the double bond and yield two carbonyl compounds. The ozonolysis product (C) can be:

\[ \text{C} = \text{CH}_3\text{C(=O)H} + \text{CH}_3\text{C(=O)CH}_2\text{CH}_2\text{CH}_3 \]

This means compound (C) consists of an aldehyde and a ketone.

### Step 4: Formation of Compound (D) from (C)
When compound (C) is treated with a base, it can undergo a reaction to form **1-acetylcyclopentene (D)**. The mechanism involves the formation of a cyclic structure, which can be represented as:

\[ \text{D} = \text{1-acetylcyclopentene} \]

### Step 5: Reaction of Compound (B) with HBr
Compound (B) can also react with HBr to yield compound (E). The product (E) will be an alkyl halide, specifically:

\[ \text{E} = \text{Brominated product} \]

### Summary of Structures
1. **Compound (A)**: Cyclohexanone (C6H10O)
2. **Compound (B)**: 2-Methyl-2-pentanol (C6H12O2)
3. **Compound (C)**: A mixture of acetaldehyde and a ketone
4. **Compound (D)**: 1-Acetylcyclopentene
5. **Compound (E)**: Brominated product of (B)