Groups Of Water Molecules Research Articles

Hydrate structures, intermolecular interactions and proton conducting mechanism in polyelectrolyte membranes — infrared results

5 μm thick membranes of polyelectrolytes were studied by IR spectroscopy. p] Salts at low degree of hydration (about two water molecules per fixed ion): It is shown that in the case of salts of polystyrene sulfonic acid the cations are present at the —SO 3 − groupings. They are attached asymmetrically to these groupings which they crosslink in the cases of di- and trivalent cations. The water molecules are attached with their lone pairs to the cations and are bound via hydrogen bonds to the anions. The strength of these hydrogen bonds is increased, due to both the polarization of the OH groups of the water molecules caused by the cation fields, as well as the interaction of the lone pairs with d-holes of transition element ions. With cations with hydrophobic character, and with monovalent cations in the series Li + → Cs +, increasing clustering of water molecules is observed. p]With increasing degree of hydration the cation—anion interaction is increasingly weakened. The same is true with regard to the hydrogen bonds formed by the OH groups of the hydration water molecules. The attachment of a second layer of hydration molecules and the proteolytic splitting of water molecules in the membranes is discussed. p] Acidic forms of the membranes: In thoroughly dried membranes, the acid groups are always crosslinked via hydrogen bonds. In the weak acids, these groupings also remain crosslinked at high degrees of hydration. With the strongly acidic polystyrene sulfonic acid, these hydrogen bonds are already broken at low degrees of hydration. H 5O 2 + groupings are formed. The hydrogen bond in this grouping shows great proton polarizability, as indicated by an intense continuum. The nature of the H 9O 4 + grouping is discussed on the basis of these results. Finally, it is shown that the great proton polarizability of the hydrogen bond in H 5O 2 + is the ultimate reason of the Grotthus conductivity.

Structure of the hydrated electron

We study the short range interactions between an electron and the neighbor water molecules, with a modified version of the CNDO/2 method. The basis set used includes excited atomic orbitals which are fundamental in the study of the system (H2O)n−. Our calculations indicate that the electron is not associated to a vacancy or other type of defect but to a group of water molecules in the normal microscopic structure of ice and liquid water. In ice it can also be considered as an extra electron in an otherwise perfect crystal lattice (an electronic polaron). Our results are consistent with the hydration energy, spectra, and photobleaching experiments.

STUDY OF SLOW MOTION OF WATER MOLECULES IN ROCHELLE SALT AND IN AMMONIUM ROCHELLE SALT BY SPIN-LATTICE RELAXATION OF PROTONS IN ROTATING FRAME

Abstract. - Temperature and frequency dependence of spin-lattice relaxation time in rotating frame Tlr of protons in Rochelle salt and in ammonium Rochelle salt was measured. Two groups of water molecules, called by Bjorkstam [I] A, B, C, D and a, D,y, S water molecules were studied and the correlation time zc was determined for both groups. No direct contribution of water molecules to ferroelectric dipoles was found. Measurements of Tlr of protons in 7.8 mol% ammonium Rochelle salt were performed to check our conclusions, obtained for Rochelle salt. Comparison is made with the dielectric measurements on Rochelle salt at 298 OK. Introduction. - The first known ferroelectric Rochelle salt [2] (R. S.) NaKC,H,O,. 4 H,O is still interesting since there are several open questions in the dynamics of crystal lattice, in particular at both ferro- electric transitions. R. S. is one of the few ferro- electrics with two transition temperatures and with the ferroelectric phase between the transition tempera- tures : 24 OC and

A molecular orbital calculation for the hydrated electron

The energy of the hydrated electron was calculated for several groups of water molecules. A molecular orbital calculation with the CNDO/2 approximation was used. The results do not indicate cavity formation but favor a normal ice-like structure.