the electronic structure of the nitrogen atoms of allyl (5- pyridin-2-yl-[1,3,4]-thiadiazol-2-yl)-amine烯丙基的氮原子的电子结构(5 - pyridin-2-yl[1,3,4]-thiadiazol-2-yl)胺.pdf

Int. J. Mol. Sci . 2006, 7, 231-254 International Journal of Molecular Sciences ISSN 1422-0067 © 2006 by MDPI /ijms/ Full Paper The Electronic Structure of the Nitrogen Atoms of Allyl (5- pyridin-2-yl-[1,3,4]-thiadiazol-2-yl)-amine Leokadia Strzemecka Department of Organic Chemistry, Faculty of Pharmacy, Medical Academy of Lublin, Staszica 6, 20-081 Lublin, Poland; e-mail: leokadia.strzemecka@am.lublin.pl; fax: +48-81 532 89 03 Received: 28 February 2006; in revised form: 18 May 2006 / Accepted: 20 May 2006 / Published: 28 June 2006 Abstract. The resonance structures of allyl-(5-pyridin-2-yl-[1,3,4]-thiadiazol-2-yl)-amine 1 13 15 have been determined by means of its H- (100 MHz, 500 MHz) C- and N-NMR spectra and B3LYP/6-31G* computations. The tautomeric equilibrium of this compound has been observed in the 1H-NMR spectra (100 MHz). Keywords: Allyl-(5–pyridin–2-yl-[1,3,4]-thiadiazol–2–yl)-amine; electronic structure, tautomerism Introduction 1,3,4-Thiadiazoles bearing an amino group at the C2 atom can exist in different tautomeric forms (Figure 1). The tautomeric equilibrium is influenced by the exocyclic N6 and C5 substituents on the 1,3,4-thiadiazole ring [1, 2]. 2-Amino-[1,3,4]-thiadiazole exists in the amino form in solution and in the solid state. The same tautomer is the main form in 5-alkoxy d