Showing papers by "Rosa M. Claramunt published in 1998"
01 Mar 1998
TL;DR: In this paper, it was shown that dipolar solid state 15 N NMR spectroscopy can be used to estimate the positions of hydrogen bond deuterons in polycrystalline 15 N labeled proton sponges containing an intramolecular N…H…N hydrogen bond.
Abstract: It is shown that dipolar solid state 15 N NMR spectroscopy can be employed in order to estimate the positions of hydrogen bond deuterons in polycrystalline 15 N labeled proton sponges containing an intramolecular N…H…N hydrogen bond. For singly 5 N labeled 1,8-bis(dimethylamino)naphtatene LPF 6 (1-h: L=H, 1-d: L=D), an asymmetric hydrogen bond with cubic average distances between the two nitrogen atoms and the hydrogen bond deuteron of 1.19 A and 1.47 A are obtained. These values are in accordance with the N...H distances of 1.19(7) A and 1.43(6) A, obtained previously by x-ray diffraction at 150 K.
25 citations
TL;DR: In this article, a combination of calculated and experimental values were used to compare the B3LYP/6-311+G(2d,p) and B3lyP/ 6-31 +G(d) basis sets.
Abstract: Ab initio coupled GIAO calculations were carried out on 13 mono-substituted benzenes a and 21 1-substituted pyrazoles b using four different ab initio methods which led to the final selection of the hybrid B3LYP/6-311+G(2d,p)//B3LYP/6-31+G(d) basis set. Comparison with experimental chemical shifts in solution (taking into account the calculated shieldings of the corresponding references) shows the excellent agreement between both sets if one allows for a factor of proportionality of about 0.96. Some structural problems such as conformation, tautomerism and structure of salts are discussed using a combination of calculated and experimental values.
20 citations
17 citations
TL;DR: In this article, hybrid abinitio calculations (GIAO/B3LYP/6-31G*) together with new DNMR experiments (1H and 13C) have been used to clarify the problem of the conformation of 5,6,11,12-tetrahydrodibenzo[a,e]cyclooctene.
Abstract: Hybrid abinitio calculations (GIAO/B3LYP/6-31G*) together with new DNMR experiments (1H and 13C) have been used to clarify the problem of the conformation of 5,6,11,12-tetrahydrodibenzo[a,e]cyclooctene. The carbon-13 chemical shifts have been assigned unambiguously to the chair C and twist-boat TB conformations. Lineshape analysis of the 1H NMR spectra has been carried out at several temperatures using an estimated set of Karplus-type vicinal coupling constants.
16 citations
TL;DR: The molecular and crystal structure of 2-(2′-hydroxyphenyl)imidazole (2) and 1-methyl-2-(2.hydroxymhenyl)-IMIDZole (5) were determined by X-ray analysis.
16 citations
TL;DR: The molecular and crystal structure of the title compound, as determined by X-ray analysis, shows that the tautomeric form present in the solid state is 5-ethoxycarbonyl-3-hydroxypyrazole, 3.5 as discussed by the authors.
14 citations
12 citations
10 citations
Journal Article•
4 citations
TL;DR: In this article, the nature of the matrix used in Fast Atom Bombardment (FAB) analyses of pyrazolo[1,2-a]pyrazoles was found to influence significantly their positive and negative ions mass spectra.
3 citations
Journal Article•
TL;DR: In this article, the DGICYT of Spain provided financial support for the project, project numbers PB96-0001-C03-01 −1 −2 −3