Behaviour of some newly synthesized substituted 1,2,4-triazoline-3-thiones in sulfuric acid media

Mirjana Jankulovska, Ilinka Spirevska, Katica Čolančevska-Ragenović


The protonation process of some newly synthesized substituted 1,2,4-triazoline-3-thiones (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 investigated in aqueous sulfuric acid solutions, using the ultraviolet spectrophotometric method, at a room temperature. The acid-base equillibria were characterized qualitatively and quantitatively. The method of characteristic vector analysis (CVA) was used to reconstruct the experimental spectra. The protonation process, most likely occurs on the thiourea fragment of the 1,2,4-triazoline-3-thione ring. The pKBH + values were calculated using several methods: the Hammett acidity function method, Bunnett and Olsen, Tissier and Tissier (Bunnett and Olsen, Yates), Marziano, Cimino and Passerini, and the “Excess acidity" function method (Cox and Yates). There is a good agreement between the pKBH + values determined with these different methods.


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-octyl2,4-dihydro3H-1,2,4-triazoline-3-thione; UV spectrophotometry; protonation constants

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