Title : Cluster structure and unique water and alcohols properties
Abstract:
Intermolecular hydrogen bonding, which is formed between water and alcohol’s molecules, causes a variety of liquid water’ and alcohols unique properties. This report presents the experimental FT IR studies’ results of water and methanol trapped in Ar matrix at temperatures from 10 to 50 K as well as condensed water and methanol at temperatures from 100 to 370 K. It is shown that temperature evolution for FTIR-spectra of water trapped in cryo Ar-matrices can be considered as an experimental model of the water structure transformation during the phase transition from gas phase to condensed confined water [1, 2]. The FTIR spectra comparison of water in Ar-matrices with the corresponding spectra of bulk water allows us to conclude that bulk water structure consist from clusters of different sizes. These clusters are elementary volume units of hydrogen bonded networks. The comparison of the water vibrational spectra change with temperature in Ar matrix and in condensed phase allows us to conclude that intermolecular H-bonding can be seen in the water intracluster vibrational spectra. And they are absent in the isolated water molecules spectra. These vibrational spectra contain information about peculiarities of water cluster structure in cryomatrices and in condensed phase. Water cluster structure in condensed phase is changing with temperature. Number of big size clusters (4 – 6 molecules per cluster) is increasing while cooling [3]. Thus water in condensed phase is a complex cluster structure, its’ cluster composition is changing with temperature. Cluster compositions of different sizes are depicting themselves through unusual water properties with unusual behavior at different temperatures. Our investigation results allow us to consider condensed water as hydrogen bonded Continuous Molecular Networks, where molecular clusters are structural units. One must take into account that such networks are created from clusters as structural units, and for liquid water the number of molecules in each cluster is not bigger than four. Networks of super cooled water contain five-molecule clusters, what don’t allow to build the crystalline structure and explain the water density increase at temperatures below 273 K (so-called low density water). The analogous results we fixed for bulk methanol.
