Substituent Constants σp− of the Rotated Nitro Group. The Interplay Between the Substituent Effect of a Rotated −NO2 Group and H-Bonds Affecting π-Electron Delocalization in 4-Nitrophenol and 4-Nitrophenolate Complexes: a B3Reportar como inadecuado




Substituent Constants σp− of the Rotated Nitro Group. The Interplay Between the Substituent Effect of a Rotated −NO2 Group and H-Bonds Affecting π-Electron Delocalization in 4-Nitrophenol and 4-Nitrophenolate Complexes: a B3 - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Croatica Chemica Acta, Vol.82 No.1 June 2009. -

The geometries of a series of nine 4-substituted nitrophenols and 4-substituted nitrophenolates

X = H, CONH2, CHO, COOH, COCH3, COCl, CN, NO2, NO and of their conformers, where the nitro group rotates by 10º from φ = 0° to φ = 90°, were optimized at the B3LYP-6-311+G** DFT level. These

data were used to analyse the effect of rotating of the nitro group on π-electron delocalization in the ring. It has been shown that the substituent effect stabilization energy SESE estimated for p-substituted phenolates correlates very well with σp− constants. Based on this dependence the σp− constants for the nitro group as a function of the out-of-plane dihedral angle φ were obtained. Application of the model simulating varying strength of H-bond by approaching F− HF group to OH O− group of the 4-nitrophenol 4-nitrophenolate with the rotating nitro group allowed to show interrelation between changes in aromaticity of the ring due to both rotation of the nitro group and changes in the strength of H-bonding. Two indices of aromaticity: Nucleus-Independent Chemical Shifts NICS, and the Harmonic Oscillator Model of Aromaticity HOMA were used to quantify the aromatic character of the benzene fragment.

nitrophenols; DFT calculations; aromaticity; hydrogen bonding; Hammet parameters



Autor: Michał A. Dobrowolski - ; Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland Tadeusz M. Krygowski

Fuente: http://hrcak.srce.hr/



DESCARGAR PDF




Documentos relacionados