Study of Raman Scattering of Light in Liquid Arenes and Their Halogen-Substituted ones in the Low-Frequency Region of the Spectrum

Abstract

Purpose. Investigation of Raman scattering of light in liquid arenas and their halogenated ones in the low-frequency range of the spectrum, taking into account the clustering processes in their structure.Methods. Raman spectroscopy methods were used, as well as a modeling method using cluster representations of the structure of liquids. Raman spectra of light in the low-frequency range from 17 to 500 cm–1 were obtained using a LabRAM HR Evolution spectrometer at room temperature (23°C).Results. The analysis of theoretical and experimental work on the properties of dimeric configurations of benzene and on the effect of clustering processes in substances on their IR and Raman spectra is carried out. Low-frequency Raman spectra of liquid benzene, o-xylene, ethylbenzene, fluorobenzene, chlorobenzene, brombenzene, toluene, o-fluorotoluene, m-fluorotoluene, p-fluorotoluene, o-chlorotoluene, m-chlorotoluene, p-chlorotoluene, 2,4-dichlorotoluene, 2,6-dichlorotoluene were obtained. The model of formation and disintegration of cluster formations has been tested. Formulas have been obtained for estimating the minimum frequency of libration oscillations of the ωmin dimer formation in the cluster structure and the position of the maxima of spectral bands in the low-frequency region of the Raman spectrum, depending on the number of particles included in the cluster formations. The theoretical results obtained by ωmin are in satisfactory agreement with the experimental data within the total error.The proposed model makes it possible to predict the position of some spectral bands of the Raman spectrum. The presence of other spectral bands is obviously related to the multiparticle interaction in the cluster structure and requires additional research.Conclusion. The proposed model of formation and decay of cluster formations and the relations following from it allow us to estimate the value of the minimum frequency in the low-frequency range of the Raman spectrum of liquid arenes and their halogenated ones from the known values of the enthalpy of formation and the moment of inertia of the dimer. Conversely, using known values of the minimum frequency, the values of the enthalpy of formation and the moment of inertia of the dimer can be estimated without resorting to complex quantum mechanical calculations.