Theoretical and experimental analysis of properties in heterocycles containing the aminosulphonylamino moiety

Abstract

A theoretical and experimental analysis of the geometric and electronic properties of compounds containing the aminosulphonylamino moiety was carried out. The theoretical properties were calculated using molecular orbital a b initb methods at the Hartree-Fock (HF) and second order Moller-Plesset (MP2) levels of theory, local density functional (LDF) ab initio methods and the semi-ab initio method,

Solvent effect on the tautomerism of 4-aminopyrazino[2,3-c][1,2,6]thiadiazine 2,2-dioxides

“…11 Even though the semiempirical methods did not provide good results for related molecules in previous studies, they were selected due to their speed compared to ab initio methods and to obtain initial geometries for the latter calculations. 7 The molecular ab initio calculations at the RHF/ 6-31G* level have been shown to provide excellent geometrical descriptions of analogous systems and similar results have been obtained in the electronic characteristics of these molecules from DFT calculations. 7 The results of the gas phase calculations of the three possible tautomers of 1, using semiempirical (AM1 and PM3), density functional theory (BLYP/6-31G*) and molecular orbital ab initio methods (RHF/6-31G*) are gathered in Table 1.…”

“…7 The molecular ab initio calculations at the RHF/ 6-31G* level have been shown to provide excellent geometrical descriptions of analogous systems and similar results have been obtained in the electronic characteristics of these molecules from DFT calculations. 7 The results of the gas phase calculations of the three possible tautomers of 1, using semiempirical (AM1 and PM3), density functional theory (BLYP/6-31G*) and molecular orbital ab initio methods (RHF/6-31G*) are gathered in Table 1. In all the methods used, the most stable tautomer is the 1-NH, with a very large energy difference from the second most stable tautomer, the 8-NH.…”

Supportless Silver Nanowires as Oxygen Reduction Reaction Catalysts for Hydroxide‐Exchange Membrane Fuel Cells

“…Among these, the heteroaromatic ring systems are the most interesting and the quantitative assessment of the aromaticity of heterocycles has been considered 13–28. The aromaticity of five‐membered sulfur containing rings with different oxidation numbers (S, SO, and SO 2 ) and including no (thiophene), one (isothiazole), or two (1, 2, 5‐thiadiazole) adjacent heteroatoms has been previously investigated 29.…”

Sulfamides in the synthesis of heterocyclic compounds

“…Recently, the aromaticity of heterocyclic compounds has been the subject of many theoretical studies. 47,49,50 The results of ab initio quantum-chemical calculations of the electronic properties and the geometry of these molecules, which were confirmed by X-ray diffraction analysis, 47,49,50,100,101 demonstrated that the rings in 1,2,5-thiadiazole 1,1-dioxide and 1,2,6-thiadiazine 1,1-dioxide, unlike those in 2-pyrimidinones, are nonaromatic. 47 The lack of the aromaticity results from the specificity of the structure of the SO 2 group (see Section II).…”

“…Recently, the crystal structure of sulfamide has been studied by X-ray and neutron diffraction analysis (Table 1). 49,51,52 According to the results of these studies, the S and N atoms in the sulfamide molecule have tetrahedral and pyramidal bond configurations, respectively, whereas the nitrogen atom in amides and urea is characterised by sp 2 hybridisation and a planar bond configuration. 52 The urea molecule is planar and symmetrical.…”