| | 1 | Author
| Jumn-Min Fan, Yu Wang, Chuen-Her Ueng | Requires cookie* | | | Title
| Electrostatic Properties of 3-(p-Ethoxyphenyl) sydnone  | | | | Abstract
| The bonding type and characteristic chemical reactions of the sydnone ring have been rationalized by examination of the deformation electron density distribution and electrostatic potential from both experiment and theory. The net atomic charges, bond lengths and bond orders of the title compound confirm the semiaromatic bonding type for the sydnone ring. The highly negative net atomic charge of C4 suggests its susceptibility to electrophilic substitution at this position. The well known 1,3-dipolar cycloaddition reaction of the sydnone ring can be understood by the analysis of the 7 t -o r b i t a l wavefunctions, which give rise to similar deformation densities as the experimental ones. The good agreement between the experimental and theoretical (ab initio calculation using 3-21G basis sets) deformation density distribution of the title compound justifies the use of the same basis set to derive the electrostatic potential. The electrostatic potential map reveals all the possible protonation sites of the sydnone ring at Ol, N2 and 06 with the deepest hole at 06 (84.6 kcal/mole). The molecular structure of 3-(p-ethoxyphenyl)syd-none [1] is shown in Figure 1. The phenyl ring plane and the sydnone ring plane are nearly coplanar (di-hedral angle of 2°). A deformation density study of this compound is presented here using both experimental X-ray diffraction data at 110 K and a split valence basis ab-initio calculation. The deformation densities examined are Ag x _ x , Ag m _ a , and Ag mo _ ao , where ÄQx-x is from conventional X-X (high angle [2], Ag m _ a is from a multipole model [3], Ag mo _ ao is from an ab-initio calculation using a 3-21G basis set [4]. The bond lengths, bond orders and net atomic charges of this compound are presented in Table 1 with com-parison between experimental and theoretical results. Bond lengths and bond orders indicate C5-06 to be Fig. 1. Molecular drawing with thermal ellipsoids at 110 K. | | | |
Reference
| Z. Naturforsch. 48a, 105—108 (1993); received December 28 1991 | | | |
Published
| 1993 | | | |
Keywords
| Sydnone, Deformation charge density, Electrostatic potential | | | |
Similar Items
| Find | | | DEBUG INFO
| | | | | TEI-XML for
| default:Reihe_A/48/ZNA-1993-48a-0105.pdf | | | | Identifier
| ZNA-1993-48a-0105 | | | | Volume
| 48 | |
| 2 | Author
| Zhengwei Su, Philip Coppens | Requires cookie* | | | Title
| Electrostatic Properties of Molecules from the X-Ray Charge Density. Application to Deuterated Benzene, 1-Alanine and d,l-Histidine | | | | Abstract
| It has been shown (Z. Su and P. Coppens, Acta Cryst. A 48, 188 (1992)) that the electrostatic potential, the electric field, and the electric field gradient (EFG) can be expressed in closed forms in terms of the positions and the charge-density parameters of individual atoms, whose aspherical density is described by a pseudoatom model (e.g., N. Hansen and P. Coppens, Acta Cryst. A 34, 909 (1978)). A Fortran program Molprop91 based on this method has been written (Z. Su, State Univ. of New York at Buffalo 1991). The method has been applied to the title compounds. Low-temper-ature X-ray diffraction data of fully deuterated benzene (G. A. and d,/-histidine (N. Li, Ph.D. thesis, State University of New York at Buffalo 1989) were analyzed using the least-squares deformation density refinement program Lsmol90 (a modified version of Molly). Molprop91 was subsequently used to calculate the electrostatic-poten-tial maps in selected sections, and at the nuclear positions. For the latter, the EFGs were also evaluated. The electrostatic potentials were used to fit net atomic charges and estimate the molecular energies. Errors in the derived quantities are given. | | | |
Reference
| Z. Naturforsch. 48a, 85—90 (1993); received April 23 1992 | | | |
Published
| 1993 | | | |
Keywords
| Electron density, Electrostatic potential, Electric field, EFG, Molecular energy | | | |
Similar Items
| Find | | | DEBUG INFO
| | | | | TEI-XML for
| default:Reihe_A/48/ZNA-1993-48a-0085.pdf | | | | Identifier
| ZNA-1993-48a-0085 | | | | Volume
| 48 | |
|
