A 13C NMR and AM1 study on intramolecular interactions defining the methoxy group conformation in unhindered anisole derivatives

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Interactions which define the planar conformation of the methoxy group with respect to the aryl ring in methyl aryl ethers are studied by 13C NMR spectroscopy and by MO calculations at the AM1 level in a family of anisole derivatives with unhindered ortho positions. Different methoxy ortho substitue...

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Autores principales: Biekofsky, R.R., Pomilio, A.B., Aristegui, R.A., Contreras, R.H.
Formato: JOUR
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_00222860_v344_n1-2_p143_Biekofsky
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling todo:paper_00222860_v344_n1-2_p143_Biekofsky2023-10-03T14:30:38Z A 13C NMR and AM1 study on intramolecular interactions defining the methoxy group conformation in unhindered anisole derivatives Biekofsky, R.R. Pomilio, A.B. Aristegui, R.A. Contreras, R.H. Interactions which define the planar conformation of the methoxy group with respect to the aryl ring in methyl aryl ethers are studied by 13C NMR spectroscopy and by MO calculations at the AM1 level in a family of anisole derivatives with unhindered ortho positions. Different methoxy ortho substituent chemical shifts were found and they were ascribed to different populations of the two coplanar conformers of the methoxy group. Optimized geometries, total energies, total point-charge dipole moments and II bond orders of the aromatic CC bonds for both methoxy rotamers of each of these compounds were calculated. Results suggest that the different populations of both types of rotamer arise from an electrostatic interaction between the side-chain dipole moment and an opposite dipole moment induced on the II electronic system of the aromatic CipsoCortho bond oriented s-cis to the methyl moiety of the methoxy group. The strength of this interaction depends on the II bond order of that bond. The failure of the AM1 method to describe quantitatively the energy of this interaction is discussed. © 1995. Fil:Biekofsky, R.R. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Pomilio, A.B. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Aristegui, R.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Contreras, R.H. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_00222860_v344_n1-2_p143_Biekofsky
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
description Interactions which define the planar conformation of the methoxy group with respect to the aryl ring in methyl aryl ethers are studied by 13C NMR spectroscopy and by MO calculations at the AM1 level in a family of anisole derivatives with unhindered ortho positions. Different methoxy ortho substituent chemical shifts were found and they were ascribed to different populations of the two coplanar conformers of the methoxy group. Optimized geometries, total energies, total point-charge dipole moments and II bond orders of the aromatic CC bonds for both methoxy rotamers of each of these compounds were calculated. Results suggest that the different populations of both types of rotamer arise from an electrostatic interaction between the side-chain dipole moment and an opposite dipole moment induced on the II electronic system of the aromatic CipsoCortho bond oriented s-cis to the methyl moiety of the methoxy group. The strength of this interaction depends on the II bond order of that bond. The failure of the AM1 method to describe quantitatively the energy of this interaction is discussed. © 1995.
format JOUR
author Biekofsky, R.R.
Pomilio, A.B.
Aristegui, R.A.
Contreras, R.H.
spellingShingle Biekofsky, R.R.
Pomilio, A.B.
Aristegui, R.A.
Contreras, R.H.
A 13C NMR and AM1 study on intramolecular interactions defining the methoxy group conformation in unhindered anisole derivatives
author_facet Biekofsky, R.R.
Pomilio, A.B.
Aristegui, R.A.
Contreras, R.H.
author_sort Biekofsky, R.R.
title A 13C NMR and AM1 study on intramolecular interactions defining the methoxy group conformation in unhindered anisole derivatives
title_short A 13C NMR and AM1 study on intramolecular interactions defining the methoxy group conformation in unhindered anisole derivatives
title_full A 13C NMR and AM1 study on intramolecular interactions defining the methoxy group conformation in unhindered anisole derivatives
title_fullStr A 13C NMR and AM1 study on intramolecular interactions defining the methoxy group conformation in unhindered anisole derivatives
title_full_unstemmed A 13C NMR and AM1 study on intramolecular interactions defining the methoxy group conformation in unhindered anisole derivatives
title_sort 13c nmr and am1 study on intramolecular interactions defining the methoxy group conformation in unhindered anisole derivatives
url http://hdl.handle.net/20.500.12110/paper_00222860_v344_n1-2_p143_Biekofsky
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