Synthesis and Potentiometric Titrations of 3-Alkyl(Aryl)-4-[3-etoxy-4-(4-methoxybenzensulfonyloxy)-benzylidenamino]-4,5-dihydro-1H-1,2,4-triazol-5-ones

Yıl 2018, Sayı: 2, 143 - 150, 19.08.2018

Ozlem Aktas Yokus Murat Beytur Sevda Manap Haydar Yuksek

Öz

Determination
of pK_a values of the
active constituent of certain pharmaceutical preparations is important because
the distribution, transport behaviour, bonding to receptors, and contributions
to the metabolic behaviour of the active constituent molecules depend on the
ionization constant. 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 that
some 1,2,4-triazole and 4,5-dihydro-1H-1,2,4-triazol-5-one derivatives were
titrated potentiometrically with tetrabutyl ammonium hydroxide (TBAH) in
non-aqueous solvents, and the pK_a values of the
compounds were determined. In this study, the first part of the study nine
novel
3-alkyl(aryl)-4-[3-etoxy-4-(4-methoxybenzensulfonyloxy)-benzylidenamino]-4,5-dihydro-1H-1,2,4-triazol-5-ones were synthesized
from the reactions of the corresponding 3-alkyl(aryl)-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones with
2-ethoxy-4-formylphenyl 4-methoxybenzenesulfonate, which was obtained from the
reaction of 3-ethoxy-4-hydroxybenzaldehyde with 4-methoxybenzensulfonyl
chloride by using triethylamine. The new compounds synthesized were also
characterized by using IR and ¹H-NMR, ¹³C-NMR spectral
data. The second part of the study, nine novel
3-alkyl(aryl)-4-[3-etoxy-4-(4-methoxybenzensulfonyloxy)-benzylidenamino]-4,5-dihydro-1H-1,2,4-triazol-5-ones were titrated
potentiometrically with TBAH (tetrabutylammonium hydroxide) in four different
non-aqueous solvents (isopropyl alcohol, tert-butyl alcohol, acetone and N,N-dimethylformamide) and graphs were
drawn for all cases. The half notralization potentials and pK_a values were determined by
half neutralization method. The effects of solvents and molecular structure
upon acidity were also discussed.

Anahtar Kelimeler

Synthesis, 4, 5-dihydro-1H-1, 2, 4-triazol-5-one, TBAH, pKa, Half-neutralization method

Kaynakça

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