Frequently Asked Question

Hydrochloric and perchloric acids, even though they are strong acids with comparable hydrogen ion concentrations, differ from sulfuric acid in terms of their reactivity. The inability of hydrochloric acid to act as a dehydrating agent or hydrate alkenes, unlike sulfuric acid, can be attributed to several factors:

1. Water Affinity: Sulfuric acid has a strong affinity for water molecules, making it an effective dehydrating agent. It readily absorbs water from its surroundings, including from organic compounds like alkenes. Hydrochloric acid, on the other hand, has a weaker affinity for water and is less efficient in removing water molecules.

2. Nucleophilicity: In the hydration of alkenes, the acid acts as an electrophile, accepting electrons from the alkene's double bond. Sulfuric acid is a stronger electrophile compared to hydrochloric acid due to the presence of two electronegative oxygen atoms bonded to the sulfur atom. This enhanced electrophilicity makes sulfuric acid more reactive towards alkenes.

3. Formation of Intermediates: The hydration of alkenes proceeds through the formation of a carbocation intermediate. Sulfuric acid can stabilize the carbocation intermediate more effectively than hydrochloric acid due to the resonance structures involving the sulfate ion. This stabilization lowers the activation energy for the reaction, making sulfuric acid a more efficient catalyst for alkene hydration.

In summary, the differences in water affinity, electrophilicity, and intermediate stability contribute to the distinct reactivity of sulfuric acid compared to hydrochloric acid, even though they possess similar hydrogen ion concentrations.