Spectroscopic and dynamic NMR study, X-ray crystallography and DFT calculations of two phosphoramidates: (C4H3O2)P(O)(Cl)C6H14N and (C4H3O2)P(O)(C6H11NH)2
作者:F.M. Oliveira、L.C.A. Barbosa、A.J. Demuner、C.R.A. Maltha、S.A. Fernandes、J.W.de M. Carneiro、R.S. Corrêa、A.C. Doriguetto
DOI:10.1016/j.molstruc.2013.04.059
日期:2013.8
In recent years, research in organophosphorus compounds, particularly phosphoramidates, has attracted attention because of their many applications. In this work, we report a combined experimental and theoretical study on the molecular structure and NMR spectra of two phosphoramidates (furan-2-yl N,N-diisopro-pylamidochlorophosphate (1) and furan-2-yl N,N,N',N'-dicyclohexylamidophosphate (2)). In the NMR time scale a free rotation of the C-N/P N single bonds was observed at room temperature (298 K) while the rotation freezes below 195 K for compound 1. From dynamic NMR analysis, the activation free energy (AG(#)) for rotation of the C-N/P N bonds was calculated as 9.9 +/- 0.3 kcal mol(-1). The experimental data were reinforced by theoretical calculation using the density functional theory method B3LYP and the 6-31G(d) basis set which provided activation energy (AE(double dagger)) of 9.2 kcal mol(-1). The structures of compounds 1 and 2 were determined by single crystal X-ray diffraction method. Compound 1 is formed by a racemic mixture, whose presence was evidenced only in the structure determination by X-ray. (C) 2013 Elsevier B.V. All rights reserved.