HYDROGEN-BONDED STRUCTURE IN AQUEOUS SULFURIC-ACID-SOLUTIONS

X-ray and time-of-flight (TOF) neutron diffraction and Raman spectrosc opic measurements have been carried out at 25 degrees C on concentrate d aqueous sulfuric acid solutions, (H2SO4)(x)(H2O)(1-x) x = 0, 0.25, 0 .5, 0.75 and 0.86, in order to investigate the hydrogen-bonded intermo lecular structure in the solutions. me intramolecular parameters for r egular tetrahedral SO4 unit were determined from the least squares fit to observed X-ray and neutron interference terms in the range of Q gr eater than or equal to 8 Angstrom(-1). The nearest neighbor intermolec ular hydrogen-bonded distances, r(O ... D) = 2.7 Angstrom and r(O ... D) = 1.7 Angstrom, respectively determined from X-ray and neutron inte rmolecular distribution functions, exhibited both similar to 0.2 Angst rom shorter values than those reported for pure liquid water. ma isotr opic Raman spectra of O-H stretching region for solutions of higher H2 SO4 content (x greater than or equal to 0.5) indicated an extremely br oadened band centered at 3030 cm(-1), which corresponds to similar to 300 cm(-1) lower frequency shift compared with that for pure liquid H2 O. These results suggest the existence of strong hydrogen-bonded inter molecular interaction in these solutions.