Dihydrogenfosfaattiioni

The dihydrogenphosphate ion, with the chemical formula H₂PO₄⁻, is an anion derived from phosphoric acid. It is one of the three phosphate ions formed by the dissociation of phosphoric acid in water, the others being hydrogen phosphate (HPO₄²⁻) and phosphate (PO₄³⁻). In aqueous solution, the equilibrium between these species depends on the pH. At low pH values, the dihydrogenphosphate ion is the predominant form.

This ion plays a crucial role in biological systems, particularly as a component of the phosphate buffer system in cells. This buffer system helps to maintain a stable intracellular pH, which is essential for many biochemical reactions. The dihydrogenphosphate ion acts as a weak acid, donating a proton (H⁺) to neutralize any added base, and its conjugate base, the hydrogenphosphate ion, acts as a weak base, accepting a proton to neutralize any added acid.

In addition to its buffering capacity, the dihydrogenphosphate ion is a key component of adenosine triphosphate (ATP), the primary energy currency of cells. The phosphate groups in ATP are linked by high-energy phosphate bonds, and the release of energy occurs when these bonds are broken, often involving the transfer of phosphate groups, which can include dihydrogenphosphate.

Industrially, dihydrogenphosphate salts, such as monocalcium phosphate, are used as leavening agents in baking and as fertilizers due to their phosphorus content, which is a vital nutrient for plant growth.