X-RAY-DIFFRACTION AND PM3 QUANTUM-CHEMICAL CALCULATION STUDY ON 1-HYDROXYETHANE-1,1-DIPHOSPHONIC ACID-WATER COMPLEXES

X-ray diffraction measurement of 1 molar aqueous 1-hydroxyethane-1,1-d iphosphonic acid (HEDP) solution and semiempirical quantum mechanical calculations on HEDP molecule and HEDP-water complexes were performed. From X-ray diffraction experiment it has been concluded that in the f irst hydration shell each oxygen of HEDP interacts with two water mole cules and each phosphorous interacts with six water neighbor molecules . The distances are in good agreement with similar distances in HEDP-w ater complexes calculated by PM3 method.