Study Microstructure Of Salt/methanol Solution

Ion association in solution of lithium perchlorate/methanol of different concentrations has been studied by using Raman spectra as a function of concentration of lithium perchlorate. Excess spectra revealed the contributions of free ions, solvent separated ion pairs (SIP), contact ion pairs (CIP), and Clusters ({M+N-}n) in the concentrated solutions. With excess spectra, we make assignment of these ion pairings. Simultaneity, we make quantitative analysis about changes of solution conductivities by Raman spectroscopic techniques and conclude that the concentration of free ions is the only positive factor that affects the solution conductivities, while SIP and other ion pairs all reduce the solution conductivities.On the other hand, the effects of salts on the micro-structure of liquid methanol have been studied from Raman spectra. We compared excess Raman spectra of different methanolic salts at the molarity of saltχsalt~0.5% in the O-H stretching and C-O stretching region, which reflect the interactions between anions, cations and methanol molecules. In the O-H stretching region, excess spectra show obviously that anions interact with methanol with weak hydrogen bonds, and the strength of hydrogen bonds has this relationship: CH3OH-CH3OH>Cl--CH3OH>NO3--CH3OH>ClO4--CH3OH, and in the same region we do not observe the interactions between cations and methanol molecules. And in C-O stretching region, excess Raman spectra reflect obviously the interactions between anions, cations and methanol molecules, and the frequencies of C-O stretching vibration of methanol that interact with anions and cations have this relationship: CH3-OH(anions)