Synthesis and Determination of pKa Values of Some New 3,4-Disubstituted-4,5-Dihydro-1H-1,2,4-triazol-5-one Derivatives in Non-aqueous Solvents

Abstract

3-Alkyl(Aryl)-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones (2) reacted with 2-furoyl chloride and thiophene-2-carbonyl chloride to afford the corresponding 3-alkyl(aryl)-4-(2-furoylamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (3) and 3-alkyl(aryl)-4-(2-thienylcarbonylamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (4), respectively. The new compounds synthesized were characterized by using IR, 1 H-NMR, 13 C-NMR and UV spectral data together with elemental analysis. In addition, to investigate the effects of solvents and molecular structure upon acidity, compounds 3 and 4 were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents (isopropyl alcohol, tert-butyl alcohol, N,N-dimethylformamide and acetonitrile). The half-neutralization potential values and the corresponding pK a values were determined for all cases.

A Study on 4-Acylamino-4,5-dihydro-1H-1,2,4-triazol-5-ones

“…Several articles concerning the acylation of some 4,5-dihydro-1H-1,2,4-triazol-5-one derivatives have been published [1][2][3][4][5][6][7]. In addition, 1,2,4-triazole and 4,5-dihydro-1H-1,2,4-triazol-5-one derivatives are reported to show a broad spectrum of biological activities such as antifungal, antimicrobial, hypoglycemic, antihypertensive, analgesic, antiparasitic, hypocholesteremic, antiviral, anti-inflammatory, antioxidant, antitumor and anti-HIV properties [3,[8][9][10][11][12].…”

“…On the other hand, it is known that 1,2,4-triazole and 4,5-dihydro-1H-1,2,4-triazol-5-one rings have weak acidic properties, so some 1,2,4-triazole and 4,5-dihydro-1H-1,2,4-triazol-5-one derivatives were titrated potentiometrically with tetrabutylammonium hydroxide (TBAH) in non-aqueous solvents, and the pK a values of the compounds were determined [4][5][6][7][11][12][13][14][15][16][17][18].…”

Use of the sulfide minerals pyrite and chalcopyrite as electrochemical sensors in non-aqueous solutions. The potentiometric titration of weak acids in alcohols

“…Although the changes in the potential obtained with TBAH or KOH Figure 4. (a) The effect of the indicator electrode on the shape of the end-point inflexion in the potentiometric titration of benzoic acid in isopropanol using the following titrants: (1) sodium methylate, (2) TBAH, and (3) KOH; (b) the effect of the indicator electrode on the shape of the end-point inflexion in the potentiometric titration of (1-7) stearic acid and (8-10) α-Nitroso-β-naphthol in iso-propanol using the following electrodes: (1), (3), and (8) pyrite; (5), (6), and (9) chalcopyrite; and (2), (4), (7), and (10) glass; and the following titrants: (1), (2), and (5) KOH; and (3), (4), and (6 -10) TBAH; (c) the effect of the indicator electrode on the shape of the end-point inflexion in the potentiometric titration of (1-7) benzoic acid and (8-11) stearic acid in tert-butanol using the following electrodes: (1), (3), (8), and (10) pyrite; (5) and (6) chalcopyrite; and (2), (4), (7), (9), and (11) glass, and the following titrants: (1), (2), (5), (8), and (9) KOH; and (3), (4), (6), (7), (10), and (11) TBAH. a c b and the chalcopyrite sensors are lower than for the pyrite sensor, they are distinctive enough to allow the precise determination of the TEP in the titration of very weak acids.…”

“…Therefore, it is very useful for the titration of weak acids with tetrabutylamonium hydroxide (TBAH) [3] and for differentiating the titration of carboxylic acids and phenol [4][5][6]. Due to its excellent solvent characteristics, fundamental information on acid-base equilibria would be very useful [7][8][9][10][11][12][13]. In this solvent, Fritz and Gainer coulometrically titrated mineral acids, sulfonic acids, carboxylic acids, enols, imides and phenols with electrically generated TBAH [14] and with visual and potentiometric determination of the titration end point (TEP).…”

“…Therefore, like tert-butyl alcohol, iso-propyl alcohol is a very useful solvent for the titration of weak acids [3,12], for the determination of many organic compounds [4,9,[16][17][18][19], for the determination of pK a values of azlactone dyes [8] and for the potentiometric titration of some hydroxylated benzoic acids and cinnamic acids [20] using TBAH under a nitrogen atmosphere at 25°C. Aktaş et al [21] conductimetrically and potentiometrically titrated hydroxycinnamic acids using triethylamine and TBAH.…”