A study of behavior of some 5-substituted-4-phenyl-1,2,4-triazoline-3-thiones in sulfuric acid solution using characteristic vector analysis

The protonation process of 1,2,4-triazoline-3-thiones (T3T) was studied in aqueous sulfuric acid using the UV method. Characteristic vector analysis (CVA) was used to reconstruct the experimentally obtained UV spectra, to overcome difficulties in calculating the protonation constants of T3T, and to separate the effect of protonation from the generalized medium effect. pK_TH+ values were calculated using the Hammett acidity function method, the Bunnett and Olsen method, and the excess acidity function method. The obtained values for m, Ø and m^* were close to those characteristic for similar thio compounds, indicating that the protonation site in the molecule of T3T is the S atom.