1. The Role of the Double Bond in Ethene
* Ethene's double bond: Ethene contains a carbon-carbon double bond. This double bond is electron-rich, meaning it has a high concentration of electrons.
* Electrophilic attack: Concentrated sulfuric acid is a strong electrophile, meaning it is attracted to electron-rich areas. The double bond in ethene acts as a site for electrophilic attack by the sulfuric acid.
2. The Reaction with Sulfuric Acid
* Formation of an intermediate: The electrophilic sulfuric acid attacks the double bond in ethene, breaking the double bond and forming a carbocation (a positively charged carbon atom). This carbocation is then attacked by the sulfate ion (SO42-) to form an alkyl hydrogen sulfate ester.
* Solubility: This alkyl hydrogen sulfate ester is soluble in concentrated sulfuric acid due to its polar nature and the formation of hydrogen bonds.
3. Why Ethane Doesn't Dissolve
* No double bond: Ethane only has single bonds, meaning it lacks the electron-rich double bond that is essential for the electrophilic attack by sulfuric acid.
* Non-polar: Ethane is a non-polar molecule. Concentrated sulfuric acid is a polar solvent, and "like dissolves like." The lack of polarity in ethane prevents it from dissolving in the polar sulfuric acid.
In Summary:
The key difference lies in the reactivity of the two molecules. Ethene's double bond allows for a reaction with concentrated sulfuric acid, forming a soluble product. Ethane, lacking a double bond, does not react and therefore remains insoluble.
