Thermodynamic Ionization Constants of Some Ortho-Substituted Guaiacol Derivatives.

A complete ionization scheme for tyrosine, and the ionization constants of some tyrosine derivatives.

Tyrosine, in strongly acid solution, contains 3 dissociable protons, attached respectively to the carboxyl, the aromatic hydroxyl, and the ammonium group, which we denote for convenience as Groups 1, 2, and 3 respectively, in the following discussion. Since each of the three groups may exist in either of two states (the acidic state, with the proton on, or the basic state with the proton off‘) ...

Genetic Incorporation of Seven ortho-Substituted Phenylalanine Derivatives

Crystal structures of three ortho-substituted N-acyl­hydrazone derivatives

To explore the effect of the nature of substitutions on the structural parameters and hydrogen-bond inter-actions in N-acyl-hydrazone derivatives, the crystal structures of three ortho-substituted N-acyl-hydrazone derivatives, namely (E)-N-{2-[2-(2-chloro-benzyl-idene)hydrazin-yl]-2-oxoeth-yl}-4-methyl-benzene-sulfon-amide, C16H16ClN3O3S (I), (E)-N-{2-[2-(2-methyl-benzyl-idene)hydrazin-yl]-2-ox...

Calculation of Acidity Constants of Some Substituted Thiazole Derivatives Using DFT and UV Spectroscopic Methods

The acidity constants of the compounds, including five-membered heterocyclic (pyrrole, thiophene, furan or thiazole) ring systems were determined at 25oC in aqueous solitions, applying UV-Vis spectroscopic method that uses absorbance diagrams,. In order to explain the pKa values obtained, also the molecule conformations of the bases and their corresponding conjugate acids were investigated, app...

Spectrophotometric Determination of Acidity Constants of Some Anthraquinone Derivatives in Methanol-Water Mixtures

A spectrophotometric method is used to determine the acidity constants of some derivatives of 9,10-anthraquinone in binary methanol-water mixtures at 25 °C. There is a linear inverse relationship between pKa of all acids and the mole fraction of methanol in the mixed solvent. The influence of substituents in the molecular structure on the ionization constants is discussed.