Base Strength of Various Organic Oxides

The protonation constants pKa of various aromatic substituted organic oxides are reported. The following order of increasing basicities of the investigated organic oxides was established: sulphoxides, phosphine oxides, pyridine-N-oxides, selenoxides, arsine oxides, antimony oxides and tellurium oxides. Several effects, affecting the base strength of the investigated organic oxides, such as back donation, electronegativity of the element, its polarizability and inductive effect of the radicals bound to the element are discussed

Base Strength of Various Organic Oxides

The protonation constants pKa of various aromatic substituted organic oxides are reported. The following order of increasing basicities of the investigated organic oxides was established: sulphoxides, phosphine oxides, pyridine-N-oxides, selenoxides, arsine oxides, antimony oxides and tellurium oxides. Several effects, affecting the base strength of the investigated organic oxides, such as back donation, electronegativity of the element, its polarizability and inductive effect of the radicals bound to the element are discussed

Gran's plots for end point detection in potentiometric titration of wine

In several samples of Slovenian white wine the concentration of ethanol in extract, pH values, and total acidity were determined, as well as the densities and refractive indices. Total acidity was determined by a classical procedure which is the accepted method of the American Society of Enologists and the AOAC, i.e. the titration of wine with a strong base up to the titration “end point" at pH 8.2. In order to find the true end point, Gran's graphical procedure was employed and some examples of its practical application are illustrated. A Gran's plot converts a logarithmic response to a linear plot and it is shown that in spite of the complex wine matrix, this analytical procedure enables a precise, reproducible and accurate determination of the total acidity of wine