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Start Over Author "Piro, Oscar" Journal journal of molecular structure
33 results on '"Piro, Oscar"'

31. Structure of indazole N 1-oxide derivatives studied by X-ray, theoretical methods, 1H, 13C, 15N NMR and EI/MS

Author

Gerpe, Alejandra, Piro, Oscar E., Cerecetto, Hugo, and González, Mercedes

Subjects
*MOLECULAR structure, *NITROGEN oxides, *X-ray crystallography, *NONMETALS
Abstract

Abstract: A series of indazole N 1-oxide derivatives has been spectroscopically studied in solution using 1H, 13C, and 15N NMR based on pulsed field gradient selected PFG 1Hsp sp="0.25" />= 13C and 15N) gHMQC and gHMBC experiments. Some indazoles were prepared using a new methodology to compare its spectral and structural data with the indazole N 1-oxide parent compounds. The 13C resonances of the indazole N 1-oxide carbon 3 and 7a demonstrate the N-oxide push-electron capability. The 15N resonances of the indazole N-oxide, nitrogen 1, are near to 30ppm more shielded than the corresponding values in the indazole heterocycle (deoxygenated form). Moreover, the structures of one indazole and one indazole N-oxide were unambiguously confirmed by X-ray crystallography. The solid state structures were contrasted with the theoretical ones obtained in vacuo at different calculus level. The aromaticity of the derivatives was studied analyzing the Hg constants of indazole’s aromatic hydrogens and measuring Ces in the solid state. The fragmentation that takes place in EI/MS was gathered for all the indazole N-oxide derivatives and the general fragmentation pattern analyzed. [Copyright &y& Elsevier]

Published
2007
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32. Crystal structure and spectroscopic properties of N′-methoxycarbonylsulfenyl-substituted ureas, CH3OC(O)SN(H)C(O)NRR′ [R = H, R′ = C(CH3)3 and R = R′ = CH2CH3]

Author

Torrico-Vallejos, Sonia, Erben, Mauricio F., Ruiz, Santiago Gómez, Hey-Hawkins, Evamarie, Echeverría, Gustavo A., Piro, Oscar E., and Della Védova, Carlos O.

Subjects
*CRYSTAL structure, *METHOXYCARBONYL compounds, *METHYL groups, *X-ray diffraction, *VIBRATIONAL spectra, *QUANTUM chemistry
Abstract

Structural and spectroscopic properties of N,N-diethyl- (I) and N-tert-butyl-N′-methoxycarbonylsulfenyl urea (II) are analyzed using a combined approach with data obtained from X-ray diffraction, vibrational spectra and quantum chemical calculations. The molecular structures of CH3OC(O)SN(H)C(O)N(CH2CH3)2 (I) and CH3OC(O)SN(H)C(O)N(H)C(CH3)3 (II), the later co-crystallized with ethyl acetate (II 1/2EtOAc), were determined by X-ray diffraction methods. Compound I crystallizes in the triclinic space group P-1 and II·0.5EtOAc in the orthorhombic space group Pnma. In I, there are two independent but closely related molecules in the asymmetric unit whose conformations differ only in the orientation of the terminal N(CH2CH3)2 groups. Neighboring molecules in I exhibit N-H⋯O interaction giving rise to a polymeric chains. The conformation of the O-C=O-S-N-C=O-N skeleton of II is almost identical to the corresponding one of both molecules of I. Neighboring molecules in II are linked through bifurcated N-H⋯O⋯H-N interactions giving rise to a polymeric chain. The vibrational properties have been studied by FTIR and FT-Raman spectroscopy along with quantum chemical calculations at the B3LYP/6-311+G* level. [Copyright &y& Elsevier]

Published
2013
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33. Structural effects and hydrogen bonds on N,N′-di(methoxycarbonylsulfenyl)urea, [CH3OC(O)SNH]2CO, studied by experimental and theoretical methods

Author

Torrico Vallejos, Sonia, Erben, Mauricio F., Boese, Roland, Piro, Oscar E., Castellano, Eduardo E., and Della Védova, Carlos O.

Subjects
*MOLECULAR structure, *HYDROGEN bonding, *UREA, *HYDROLYSIS, *CHEMICAL reactions, *NUCLEAR magnetic resonance spectroscopy, *CONFORMATIONAL analysis
Abstract

Abstract: Pure N,N′-di(methoxycarbonylsulfenyl)urea, [CH3OC(O)SNH]2CO, is quantitatively prepared by the hydrolysis reaction of CH3OC(O)SNCO and characterized by 1H NMR, GC–MS and FTIR spectroscopy techniques. Structural and conformational properties are analyzed using a combined approach with data obtained from X-ray diffraction, vibrational spectra and theoretical calculation methods. The IR and Raman spectra for normal and deuterated species are reported. The crystal structure of [CH3OC(O)SNH]2CO was determined by X-ray diffraction methods. The substance crystallizes in the orthorhombic P21212 space group with a =9.524(2), b =12.003(1), c =4.481(1)Å, and Z =2 moieties in the unit cell. The molecule is sited on a twofold crystallographic axis (C 2) parallel to c and shows the anti–anti conformation (S–N single bonds antiperiplanar with respect to the opposite C–N single bonds in sulfenyl-ureasic group). Neighboring molecules are arranged in a chain motif that extends along the C 2-axis and is held by bifurcated NH⋯O⋯HN intermolecular bonds. A local planar symmetry is observed in the crystal for the central –SN(H)C(O)N(H)S– skeleton. Experimental and calculated data allow to trace this structural feature to the occurrence of N–H⋯On bonding interactions. Calculated vibrational and structural properties are in good agreement with the experimentally determined features. [Copyright &y& Elsevier]

Published
2009
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