Hindered rotation around the aryl-to-nitrogen bond of n-acetyl,n-ethoxycarbonylmethyl-2-amino, 5-nitrothiophen |
| |
Authors: | D. Nicole J-J. Delpuech M. Wierzbicki D. Cagniant |
| |
Affiliation: | Laboratoire de Chimie Physique Organique, ERA CNRS 222, Université de Nancy I, C.O. 140, 54037 Nancy Cedex, France;Laboratoire de Chimie Organique, Université de Metz, Ile du Saulcy, 57000 Metz, France |
| |
Abstract: | Two stereoisomers of the title compound are observed by H NMR at 10°. Their spectra coalesce at higher temperature (10°-90°). The equilibrium and rate constants K and k, strongly dependent on the solvent used (1,4-dioxane, tetrahydrofuran, acetone, chloroform); typical values for these parameters and the related thermodynamic functions are: K(25°)= 0.170; k(25°)=23.2s?1; ΔHR and ΔH≠=4.94 and 17.9 kcal.mol.?1; ΔSR and ΔS≠ =13.1 and 7.7 e.u, in a 0.2 molar solution in 1,4-dioxane. The two isomers are shown to result from a hindered rotation around the aryl-to-nitrogen bond, presumably due to a direct resonance effect between the amide and nitro groups. The more abundant isomer was assigned a planar molecular structure in which the O atom of the amide group is close to the S atom of the thiophen ring, presumably on account of an electrostatic interaction between these two atoms which bear partial electrical charges of opposite sign. |
| |
Keywords: | |
本文献已被 ScienceDirect 等数据库收录! |
|