disulfuric

Disulfuric, commonly referred to as disulfuric acid or pyrosulfuric acid, is the chemical species with the formula H2S2O7. It is a strong, dibasic acid and a powerful dehydrating agent. In solution it behaves as a highly hydrated species and rapidly hydrolyzes to sulfuric acid. Structurally, it consists of two sulfur trioxide units linked by an anhydride bond, effectively the condensation product of two H2SO4 units. When exposed to water, it reverts to sulfuric acid.

Preparation and occurrence typically involve the condensation of sulfuric acid and sulfur trioxide. Industrially, disulfuric acid is encountered in oleum, mixtures of sulfuric acid with dissolved SO3, where the amount of dissolved SO3 defines the degree of condensation toward H2S2O7. The equilibrium H2SO4 + SO3 ⇌ H2S2O7 shifts with temperature and SO3 partial pressure, allowing control of the disulfuric species in the mixture.

Properties and uses: as a dehydrating agent, disulfuric acid removes water from substrates, driving reactions such as esterifications and sulfonations. It can activate alcohols to form sulfate esters and is used in organic synthesis to promote dehydration and condensation reactions. It also serves in the preparation of sulfate esters and in certain sulfonation processes, where strong dehydrating conditions are advantageous.

Safety and handling: disulfuric acid is highly corrosive and contact with skin or eyes can cause severe damage. It reacts violently with water, releasing heat and sulfuric acid; therefore it is handled under strict safety protocols, in appropriate containment and with personal protective equipment.