Pentane-1,5-bis­phospho­nic acid

The title compound, C₅H₁₄O₆P₂ or (CH₂)₅[PO(OH)₂]₂, commonly known as 1,5-pentyl­enebisphospho­nic acid, was prepared by hydro­lysis of the corresponding tetra­eth­yl pentyl­enebisphospho­nate with 6 M HCl. Crystals suitable for X-ray crystallography were obtained upon cooling a hot saturated 1:1 (v/v) acetone-ethanol solution of the acid to room temperature. The compound exists in the solid state as a hydrogen-bonded extended structure.