Determination of the dissociation constants of some newly synthesized derivatives of 1,2,4-triazoline-3-thione in sodium hydroxide media

Mirjana Jankulovska, Ilinka Spirevska, Lidija Šoptrajanova


The behaviour of some newly synthesized derivatives of 1,2,4-triazoline-3-thione (4-butyl-5-octyl-2,4-dihydro-3H-1,2,4-triazoline-3-thione, 4-allyl-5-octyl-2,4-dihydro-3H-1,2,4-triazoline-3-thione, 4-phenyl-5-octyl-2,4- dihydro-3H-1,2,4-triazoline-3-thione) was studied in aqueous sodium hydroxide solutions at different pH values with UV spectroscopy. The measurements were carried out immediately after preparation of the solutions, in the wavelength range from 190 nm to 360 nm, on a Varian Cary UV spectrophotometer. When the pH value of the solution increased from 5 to 9, the measured value of the absorbance decreased, while the absorption maximum shifted towards lower wavelengths. The dissociation constants were determined using the equation pKBH = logI + pH (I = c(BH)/c(B)). The ionic strength of the solutions of 0.10 mol/dm3 was adjusted with addition of NaClO4. The calculations were derived from the values of the absorbance from the spectra obtained experimentally and from the spectra reconstructed by using the method of characteristic vector analysis (CVA). The absorbance values were measured at four wavelengths, on and around the absorption maxima for each investigated compound. Also, the pKBH values were determined graphically and they were in good agreement with those obtained numerically. The obtained values of the pKBH were in the range from 7.45 to 7.54 and they were in a good agreement with the expected ones for this kind of compounds.


4-buthyl-5-octyl-2,4-dihydro-3H-1,2,4-triazoline-3-thione; 4-allyl-5-octyl-2,4-dihydro-3H-1,2,4- triazoline-3-thione; 4-phenyl-5-octyl-2,4-dihydro-3H-1,2,4-triazoline-3-thione; dissociation constant; UV spectroscopy; dissociation

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