Int. J. Mol. Sci. 2008, 9(1), 12-32; doi:10.3390/ijms9010012
Article

Preparation, GIAO NMR Calculations and Acidic Properties of Some Novel 4,5-dihydro-1H-1,2,4-triazol-5-one Derivatives with Their Antioxidant Activities

Haydar Yüksek 1,* email, Muzaffer Alkan 2 , Ismail Cakmak 1 , Zafer Ocak 2 , Şule Bahçeci 3 , Mustafa Calapoğlu 2 , Mahfuz Elmastaş 4 , Ali Kolomuç 3  and Havva Aksu 1
1 Department of Chemistry, Kafkas University, 36100 Kars, Turkey 2 Education Faculty, Kafkas University, 36100 Kars, Turkey. 3 Fatih Education Faculty, Karadeniz Technical University, 61080 Trabzon, Turkey. 4 Department of Chemistry, Gaziosmanpaşa University, Tokat, Turkey.
* Author to whom correspondence should be addressed.
Received: 12 November 2007; in revised form: 14 December 2007 / Accepted: 14 December 2007 / Published: 8 January 2008
(This article belongs to the Section Physical Chemistry, Theoretical and Computational Chemistry)
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Abstract: Six novel 3-alkyl(aryl)-4-(p-nitrobenzoylamino)-4,5-dihydro-1H-1,2,4-triazol-5- ones (2a-f) were synthesized by the reactions of 3-alkyl(aryl)-4-amino-4,5-dihydro-1H- 1,2,4-triazol-5-ones (1a-f) with p-nitrobenzoyl chloride and characterized by elemental analyses and IR, 1H-NMR, 13C-NMR and UV spectral data. The newly synthesized compounds 2 were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents such as acetone, isopropyl alcohol, tert-butyl alcohol and N,Ndimethylformamide, and the half-neutralization potential values and the corresponding pKa values were determined for all cases. Thus, the effects of solvents and molecular structure upon acidity were investigated. In addition, isotropic 1H and 13C nuclear magnetic shielding constants of compounds 2 were obtained by the gauge-including-atomic-orbital (GIAO) method at the B3LYP density functional level. The geometry of each compound has been optimized using the 6-311G basis set. Theoretical values were compared to the experimental data. Furthermore, these new compounds and five recently reported 3-alkyl-4-(2- furoylamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (3a-c,e,f) were screened for their antioxidant activities.
Keywords: 4; 5-Dihydro-1H-1; 2; 4-triazol-5-ones; Acylation; Density functional calculations; GIAO; Antioxidant activity; pKa; Potentiometric titrations

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MDPI and ACS Style

Yüksek, H.; Alkan, M.; Cakmak, I.; Ocak, Z.; Bahçeci, Ş.; Calapoğlu, M.; Elmastaş, M.; Kolomuç, A.; Aksu, H. Preparation, GIAO NMR Calculations and Acidic Properties of Some Novel 4,5-dihydro-1H-1,2,4-triazol-5-one Derivatives with Their Antioxidant Activities. Int. J. Mol. Sci. 2008, 9, 12-32.

AMA Style

Yüksek H, Alkan M, Cakmak I, Ocak Z, Bahçeci Ş, Calapoğlu M, Elmastaş M, Kolomuç A, Aksu H. Preparation, GIAO NMR Calculations and Acidic Properties of Some Novel 4,5-dihydro-1H-1,2,4-triazol-5-one Derivatives with Their Antioxidant Activities. International Journal of Molecular Sciences. 2008; 9(1):12-32.

Chicago/Turabian Style

Yüksek, Haydar; Alkan, Muzaffer; Cakmak, Ismail; Ocak, Zafer; Bahçeci, Şule; Calapoğlu, Mustafa; Elmastaş, Mahfuz; Kolomuç, Ali; Aksu, Havva. 2008. "Preparation, GIAO NMR Calculations and Acidic Properties of Some Novel 4,5-dihydro-1H-1,2,4-triazol-5-one Derivatives with Their Antioxidant Activities." Int. J. Mol. Sci. 9, no. 1: 12-32.

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