DOI•
Second derivative analysis of S=O stretching band in Raman spectra of dimethyl sulphoxide in carbon tetrachloride and water
01 Dec 1985-Vol. 95, Iss: 5, pp 499-508
TL;DR: In this paper, the S=O stretching region of the Raman spectra of a solution of a mixture of carbon tetrachloride and water was studied by second derivative analysis and the existence of equilibria between various associated species, involving dipolar and hydrogen bonding interactions, was suggested.
Abstract: Raman spectra of solutions ofdmso (dimethyl sulphoxide) are studied in the S=O stretching region by second derivative analysis. Broad bands observed in the normal Raman spectra show well resolved components in the derivative plots. On the basis of the various components obtained in these plots for solutions ofdmso in carbon tetrachloride and water, existence of equilibria between various associated species, involving dipolar and hydrogen bonding interactions, is suggested. It is concluded that solutions ofdmso in CCl4 may have monomers, cyclic and linear dimers and polymers, whereas its aqueous solutions show the existence of 1:1 and 1:2 hydrogen bonded complexes of water withdmso in addition to smaller concentrations of monomers, dimers and polymers.
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TL;DR: In this paper, a Ramaman study of cation and anion solvation in dimethyl sulfoxide, propylene carbonate and dimethyl carbonate solutions of six lithium salts has been performed in the concentration range from 0.05 to 0.25 molar fraction of a salt.
26 citations
TL;DR: In this article, an analysis of the Raman spectra of solutions of lithium salts in dimethyl sulfoxide, propylene carbonate, and dimethyl carbonate in a concentration range from diluted solutions to the mixtures of molten solvates with salts is performed in terms of the dynamics, specifically, dephasing (τV ) and modulation (τω) times of all molecular entities present in solutions are determined and analyzed.
Abstract: An analysis of the Raman spectra of solutions of lithium salts in dimethyl sulfoxide, propylene carbonate, and dimethyl carbonate in a concentration range from diluted solutions to the mixtures of molten solvates with salts has been performed in terms of the dynamics, specifically, dephasing (τV ) and modulation (τω) times of all molecular entities present in solutions are determined and analyzed. It has been found that, in the picosecond time domain, dephasing and modulation in solvent molecules hydrogen-bonded with an anion and/or solvating a cation are slower than in free solvent molecules. In solvent separated ion pairs, both τV and τω are much longer than in solvated anions, thus indicating strong interactions between anions and their surrounding. In contact ion pairs, τV are great, whereas τω appear close to those for free anions. This reflects that the structure of the liquid tends to the structure of molten salts.
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17,427 citations
824 citations
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TL;DR: In this paper, a review of the various factors involved in curve fitting of vibrational band systems is presented, with particular reference to vibrational bands, and other types of overlapping band systems encountered in analytical work are considered in less detail.
Abstract: There is an increasing awareness that the separation of over-lapping bands by the mathematical technique of curve fitting offers many pitfalls and should not be undertaken lightly. This review discusses critically the various factors involved, with particular reference to vibrational band systems; other types of overlapping band systems encountered in analytical work are considered in less detail. Five parameters are involved: the number of component bands, their positions, shapes and widths, and the form of the baseline. Curve fitting, by a least squares optimization method to a suitable goodness of fit criterion, is considerably facilitated if approximate values for some of the parameters are known at the outset. The methods available for peak finding are discussed and, although not free from problems, are reasonably effective. Similarly, band shapes can usually be defined semiquantitatively. However, it is seldom possible to obtain prior information on band widths; these should be determined during the curve fitting calculations. Although statistical goodness of fit criteria are available they should be used in conjunction with a visual plot, to locate any regions of poor fit. Furthermore, the overriding consideration must always be that the computer fit is plausible in terms of acceptable chemical species for the system being examined.
355 citations
TL;DR: In this article, a small computer on line with a single-beam spectrophotometer was used to obtain absorption spectra and higher derivatives (up to the fourth) of the absorption spectrum.
Abstract: — –A small computer on line with a single-beam spectrophotometer was used to obtain absorption spectra and higher derivatives (up to the fourth) of the absorption spectra. The spectral resolution was markedly enhanced in the higher derivative curves. The computer was also used to synthesize absorption spectra from Gaussian, Lorentzian and mixed Gaussian-Lorentzian band shapes in order to explore the higher derivative analysis of completely defined spectra.
288 citations
TL;DR: In this article, a graphical study of the behavior of the derivative curves for overlapping absorption bands of differing heights, widths and separation intervals and the derivatives are compared with the corresponding extinction and percent transmission curves.
Abstract: In the measurement of absorption spectra, it is difficult to detect low intensity bands overlapped by bands of higher intensity. Their detection is greatly facilitated by measuring the first derivative of the transmission curve with respect to wavelength. A machine is under development in this laboratory to plot this derivative. A graphical study is here made of the behavior of the derivative curves for overlapping absorption bands of differing heights, widths and separation intervals and the derivatives are compared with the corresponding extinction and percent transmission curves. The curves here presented are intended as illustrations of the possibilities inherent in derivative spectrophotometry and for the identification of extinction or transmission curve types from measured derivatives.
165 citations