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    The calculation of solvatochromic shifts: the n-π* transition of acetone
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    Uracil derivatives are potentially biologically active compounds, so the investigation of their physical and chemical properties is very important for their further application. In this work a series of newly synthesized derivatives of uracil was investigated by applying the spectrophotometric method. The absorption spectra were recorded in seventeen solvents with different properties. The effect of solvent was interpreted by Kamlet-Taft solvatochromic model. The dominance and the types of interactions that occur between the investigated derivatives and solvent were interpreted by applying the multiple linear correlation obtained values of absorption maxima and Hansen's solvent parameters. In addition to the effect of solvent, the influence of substituents in the molecule on absorption spectra was studied by applying Hammett equation.
    Solvatochromism
    Uracil
    Citations (0)
    The influence of solvent polarity on the absorption spectra of some synthesized azo dye with heterocyclic moieties and ${\beta}$-naphthol (1-3) have been investigated using a UV-Visible spectrophotometer. The spectral characteristics of the azo dyes (1-3) in different solvents at room temperature were analyzed. The solvatochromic empirical variables like ${\pi}^*$, ${\alpha}$, and ${\beta}$ have been used to discuss the solvatochromic behaviour of the dyes and to evaluate their contributions to the solute-solvent interactions. A multi-parameter regression model for quantitative assessment of the solute/solvent interaction and the absorption has been used to explain the solvent effect on azo dyes (1-3).
    Solvatochromism
    Solvent polarity
    Polarity (international relations)
    Citations (16)
    New measurements of the solvent effect on the nitrogen hyperfine coupling constant of di-tert-butyl nitroxide are reported. These, together with literature data, are used to test various models for the solvent effect. At the Hückel level of approximation, aN is a linear function of the applied electric field. Thus various reaction field theories may be considered. The widely used Onsager reaction field does not account for the effects of the more polar solvents or for the differences between polar and nonpolar solvents. The Wertheim and Block–Walker reaction fields are better, especially for very polar solvents. However none of these continuum reaction fields is entirely satisfactory theoretically or experimentally. We propose a dipole–dipole model for polar solvents which is superior to the continuum models. From the dipole–dipole model, we suggest that the quantity μρ/M is a convenient linear parameter for polar solvent effects, the factors being solvent dipole moment, density, and molecular weight. The dipole–dipole model should apply to a wide range of polar solutes. Some special situations are not explained by the model, including hydrogen-bonding solvents, halogenated aromatics, and solvents with more than one conformation. The temperature dependence of the solvent effect is also considered.
    Chemical polarity
    Citations (84)