Hydrogen-bonded structure in concentrated aqueous phosphoric acid solutions

Citation
Y. Kameda et al., Hydrogen-bonded structure in concentrated aqueous phosphoric acid solutions, B CHEM S J, 73(5), 2000, pp. 1105-1112
Citations number
40
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Chemistry
Journal title
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN
ISSN journal
0009-2673 → ACNP
Volume
73
Issue
5
Year of publication
2000
Pages
1105 - 1112
Database
ISI
SICI code
0009-2673(200005)73:5<1105:HSICAP>2.0.ZU;2-N
Abstract
Polarized Raman scattering, X-ray, and time-of-flight (TOF) neutron-diffrac tion measurements were carried out for highly concentrated aqueous phosphor ic acid solutions, in order to deduce detailed structural information on bo th the PO4-intramolecular geometry and intermolecular hydrogen bonds in the solution. Isotropic Raman spectra observed for (H3PO4)(x)(H2O)(1-x) with x = 0.1-0.6 exhibited a single band assigned to the symmetrical stretching v ibrational mode of the PO4 structural unit, which suggests that all P-O bon ds in the unit are spectroscopically equivalent. The results of X-ray and n eutron-diffraction measurements for the 53 mol% phosphoric acid solution in dicated that the structure of the PO4 unit is a regular tetrahedron with a P-O bond-length of 1.540(3) Angstrom. From a least-squares fit to the obser ved Xray and neutron intermolecular interference terms, the nearest-neighbo r intermolecular distances, reflecting intermolecular hydrogen-bonded inter actions in the solution, were determined to be r(O . . . D) = 1.77(1) Angst rom and r(O . . . O) = 2.73(2) Angstrom, respectively, which are both ca. 0 .1 Angstrom shorter than those observed for pure liquid water. Therefore, i t has been clarified that a strongly hydrogen-bonded network exists in such concentrated aqueous phosphoric acid solutions.