phosphonic acids 1,1-bis(phosphonic acid) bis(phosphonic acid) bisphosphonate chebi_ontology bisphosphonates 1,1-diphosphonic acids 1,1-bis(phosphonic acid)s 0 173.94831 diphosphonic acid CH4O6P2R2 173.98640 1,1-diphosphonic acid CHEBI:77383 bis(phosphonic acid)s Wikipedia:Bisphosphonate OP(O)(=O)C([*])([*])P(O)(O)=O 1,1-diphosphonates 1,1-diphosphonate Any member of the class of phosphonic acids in which a carbon atom is directly attached to two phosphonic acid groups. They are analogues of pyrophosphates (with the central oxygen atom replaced by a carbon atom) and like pyrophosphates they tend to have a strong affinity for bone, so are frequently used for their antiresorptive and hypocalcaemic properties.