What is the final product of the following reaction sequence?
Cyclohexanol `{:((i) conc. H_2SO_4//Delta),((ii) NBS//C Cl_4//hv),(to),((iii) Alc KOH //Delta),((iv) Br_2 //40^@C):}`

Options

A.
B.
C.
D.

Explanation

To determine the final product of the given reaction sequence starting from cyclohexanol, we will analyze each step of the reaction:

### Step 1: Dehydration of Cyclohexanol
- **Reaction**: Cyclohexanol is treated with concentrated sulfuric acid (H₂SO₄) and heated.
- **Mechanism**: The hydroxyl group (-OH) of cyclohexanol is protonated by H₂SO₄, forming an oxonium ion. This ion is unstable and loses a water molecule (H₂O), resulting in the formation of a carbocation. The most stable carbocation is formed, which is a secondary carbocation in this case.
- **Product**: The carbocation then loses a hydrogen ion (H⁺) to form cyclohexene (C₆H₁₁).

### Step 2: Bromination using NBS
- **Reaction**: Cyclohexene is treated with N-bromosuccinimide (NBS) in the presence of carbon tetrachloride (CCl₄) and light (hv).
- **Mechanism**: NBS generates bromine radicals (Br•) under light. The double bond in cyclohexene reacts with the bromine radical to form an allylic radical. This radical can stabilize through resonance.
- **Product**: The allylic radical then reacts with Br• to form allylic bromide (1-bromo-cyclohexene).

### Step 3: Elimination with Alcoholic KOH
- **Reaction**: The allylic bromide is treated with alcoholic potassium hydroxide (KOH) and heated.
- **Mechanism**: KOH acts as a base and abstracts a proton from the carbon adjacent to the bromine, leading to the elimination of HBr and formation of a conjugated diene.
- **Product**: The product is a conjugated diene (cyclohexadiene).

### Step 4: Bromination of the Conjugated Diene
- **Reaction**: The conjugated diene is treated with bromine (Br₂) at 40°C.
- **Mechanism**: The π electrons of the diene attack bromine, leading to the formation of a bromonium ion intermediate. The bromide ion then attacks the more stable position (due to resonance), leading to the formation of a dibrominated product.
- **Product**: The final product is 1,4-dibromocyclohexene, which is a thermodynamically controlled product.

### Final Product
The final product of the reaction sequence is **1,4-dibromocyclohexene**.

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