On heating glycerol with conc. `H_(2)SO_(4)` a compound is obtained which has a bad odour. The compound is :

Options

A. Glycerol sulphate
B. Acrolein
C. Formic acid
D. Allyl alcohol

Answer

To solve the problem of what compound is formed when glycerol is heated with concentrated sulfuric acid (H₂SO₄), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**:
- The reactant in this case is glycerol, which has the chemical formula C₃H₈O₃. Its structure can be represented as:
```
CH2OH
|
CHOH
|
CH2OH
```

2. **Understand the Reaction Conditions**:
- When glycerol is heated with concentrated sulfuric acid, the acid acts as a dehydrating agent. It will facilitate the removal of water (H₂O) from glycerol.

3. **Protonation of Hydroxyl Groups**:
- The hydroxyl (OH) groups in glycerol can be protonated by the sulfuric acid. This results in the formation of a good leaving group (water) from the glycerol molecule.

4. **Formation of a Carbocation**:
- After the protonation, the hydroxyl group can leave as water, creating a carbocation intermediate. This step involves the loss of water from the glycerol structure.

5. **Elimination and Rearrangement**:
- The carbocation can undergo rearrangement and elimination reactions. The hydrogen atom from an adjacent carbon can migrate to stabilize the carbocation, leading to the formation of a double bond.

6. **Formation of Acrolein**:
- The final product after dehydration and rearrangement is acrolein (C₃H₄O), which has the structure:
```
CH2=CH-CHO
```
- Acrolein is known for its pungent, bad odor.

7. **Conclusion**:
- The compound obtained from heating glycerol with concentrated sulfuric acid is acrolein.

### Final Answer:
The compound obtained is **acrolein**.

---