Solvent Effect On Frequency Shift Of Molecule Vibration Spectrum

In solution there exist sorts of interaction between solute molecular and solvent molecular ,which is reflected by the spectrum like frequency shift ,intensity and linewidth change of a vibration band .with the development of chemistry , biology and single molecular study ,it becomes imperative to study solvent effect deeply. Most of chemical reaction and physiological mechanism perform in solution . f Furthermore, many reactions were effected by solvent environment. Then solvent effect becomes important, and it is significant to study solvent effect .for example, the interaction between biomolecular enzyme and bottom substance must perform in body fluid, and its physiological function can realize. In the paper, the frequency shifts of tetramethylurea's νC=O vibration effected by more than ten sorts of solvent were calculated ,which is in order to validate the relationship between the Kirkwood parameter 21and number of acceptors number AN . From the effect of kinds of interactions consist in solvent interior , It was discussed the n ?π* electric transition of tetramethylurea's νC=O vibration effected by solvent effect,which enable the wide of energy spectroscopy were analyzed qualitatively.Through experimentation and theory calculation, we try to find a theory model and ascertain related parameter suitable for solvent effect. The theory model can reflect correctly that the frequency shift of νC=O vibration change with the solvent and solution concentration. C=O function group of tetramethylurea has strong spectroscopy by common IR and resonance Raman methods. It is the most important function group of some biology molecular, and it is through these function groups that the physiological mechanism can realize . For the simple spectroscopy of tetramethylurea we select them as samples , which will make the study of complicated molecular easier . The compare between quantum chemistry result and experimental result . will help us to establish new theory model and ascertain the related parameter, and can offer reference to suitable theory ,further more ,the calculation itself can provide the symmetry of molecular, relative intensity of vibration mode and dipole values. Experimentation was divided into IR section and Raman section . The IR section was carried on Niocolet 360FT-IRspectrum instrument , and sample pool , is CaF2 liquid groove .IR and Raman spectroscopy have complementarity in detecting molecular structure. In our experiment , the advantage of IR was that the fluorescence was avoiding ,solvent because the resonance Raman technique and together focus system were applied, the experiment validated the linear relationship between the frequency shift of C=O vibration and the number of acceptor the parameter 21. there was relation between the frequency shift and donor or acceptor number. The quantitative equation was always used in study solvent also. According to theresults synthesized from experimental data, we could conclude that the results calculated by Gutmann equation were in agreement with the experimental data better than by KBM equation . The Gutmann equation is more effective than KBM equation because of the KBM equation is based on a too oversimplified a diatomic oscillator in a continuous cavity of solvent in fact ,solvent induced vibrational frequency shifts were due to local association effects and not dielectric effects. KBM equation fit for the solvent environment the dielectric effect is very strong . Gutmann equation'donor and acceptor theory is able to reflect the local association effects. It offer a method to solve the problem with vibration frequency is effected by solvent-solute interact The paper was profound for the following study through qualitative analysis and quantitive calculation , we can see that the two physical values namely dielectric constant and dipole, can reflect the character of solvent . when the more rational equation was established ,the two physical values must be considered. some present theories also prove . This thought-way was correct . The self-consistent reaction filed theory based on consistent dielectric model quantified dipole . Certainly . The ultimate goal of this paper is in order to find a theory more suitable to for studying on solvent effect, especially ,the theory which can reflect the concentration change in trace analysis and ultra-trace analysis. The experiment used tetramethylurea as solute , put them into Carbon tetrachloride, Acetonitrile , Dimethyl sulfoxide, chloroform ,...