Conformational analysis of N-benzyl-N-o-tolyl-p-methylbenzene-sulfonamides from dynamic 1H NMR experiments and theoretical calculations

Dorota Maciejewska; Jacek Jakowski; Jerzy Kleps; Grzegorz Chałasiński

doi:10.1016/j.theochem.2004.04.024

Conformational analysis of N-benzyl-N-o-tolyl-p-methylbenzene-sulfonamides from dynamic ¹H NMR experiments and theoretical calculations

Dorota Maciejewska, Jacek Jakowski, Jerzy Kleps, Grzegorz Chałasiński

Research output: Contribution to journal › Article › peer-review

5 Scopus citations

Abstract

Theoretical studies of molecular conformations of four N-benzyl-N-o-tolyl- p-methylbenzenesulfonamides, by means of semiempirical PM3, ab initio (RHF and MP2) methods, and DFT approach, are presented and discussed in comparison with the experimental data. The free energy (ΔG^#) of rotation obtained by the dynamic shape analysis of the ¹H NMR spectra is ca. 16kcal/mol for those systems for which the barrier has been probed experimentally. Failure to determine the barrier in the experimental spectra in the case of one system is attributed to the chiral conformation of the global minimum. The rotational profile was established at the PM3 level and verified at the DFT level of theory. The solvent effect, the 0th-order vibrational corrections, and the temperature dependence of the Boltzman distribution of conformers and kinetic equilibrium are discussed.

Original language	English
Pages (from-to)	5-13
Number of pages	9
Journal	Journal of Molecular Structure: THEOCHEM
Volume	680
Issue number	1-3
DOIs	https://doi.org/10.1016/j.theochem.2004.04.024
State	Published - Jul 5 2004
Externally published	Yes

Funding

A computational grant of the Interdisciplinary Centre for Mathematic and Computer Modelling (ICM), Warsaw University is gratefully acknowledged. J.J. acknowledges support by NSF grant #9982420 to Jack Spimons and a grant of computer time provided by the Center for High Performance Computing at the University of Utah.

Funders	Funder number
National Science Foundation	9982420
University of Utah

Keywords

Dynamic H NMR
N-benzyl-N-o-tolyl-p-methylbenzenesulfonamides
Statistical mechanics simulation
Theoretical calculations

Access to Document

10.1016/j.theochem.2004.04.024

Cite this

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title = "Conformational analysis of N-benzyl-N-o-tolyl-p-methylbenzene-sulfonamides from dynamic 1H NMR experiments and theoretical calculations",

abstract = "Theoretical studies of molecular conformations of four N-benzyl-N-o-tolyl- p-methylbenzenesulfonamides, by means of semiempirical PM3, ab initio (RHF and MP2) methods, and DFT approach, are presented and discussed in comparison with the experimental data. The free energy (ΔG#) of rotation obtained by the dynamic shape analysis of the 1H NMR spectra is ca. 16kcal/mol for those systems for which the barrier has been probed experimentally. Failure to determine the barrier in the experimental spectra in the case of one system is attributed to the chiral conformation of the global minimum. The rotational profile was established at the PM3 level and verified at the DFT level of theory. The solvent effect, the 0th-order vibrational corrections, and the temperature dependence of the Boltzman distribution of conformers and kinetic equilibrium are discussed.",

keywords = "Dynamic H NMR, N-benzyl-N-o-tolyl-p-methylbenzenesulfonamides, Statistical mechanics simulation, Theoretical calculations",

author = "Dorota Maciejewska and Jacek Jakowski and Jerzy Kleps and Grzegorz Cha{\l}asi{\'n}ski",

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AU - Maciejewska, Dorota

AU - Jakowski, Jacek

AU - Kleps, Jerzy

AU - Chałasiński, Grzegorz

PY - 2004/7/5

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N2 - Theoretical studies of molecular conformations of four N-benzyl-N-o-tolyl- p-methylbenzenesulfonamides, by means of semiempirical PM3, ab initio (RHF and MP2) methods, and DFT approach, are presented and discussed in comparison with the experimental data. The free energy (ΔG#) of rotation obtained by the dynamic shape analysis of the 1H NMR spectra is ca. 16kcal/mol for those systems for which the barrier has been probed experimentally. Failure to determine the barrier in the experimental spectra in the case of one system is attributed to the chiral conformation of the global minimum. The rotational profile was established at the PM3 level and verified at the DFT level of theory. The solvent effect, the 0th-order vibrational corrections, and the temperature dependence of the Boltzman distribution of conformers and kinetic equilibrium are discussed.

AB - Theoretical studies of molecular conformations of four N-benzyl-N-o-tolyl- p-methylbenzenesulfonamides, by means of semiempirical PM3, ab initio (RHF and MP2) methods, and DFT approach, are presented and discussed in comparison with the experimental data. The free energy (ΔG#) of rotation obtained by the dynamic shape analysis of the 1H NMR spectra is ca. 16kcal/mol for those systems for which the barrier has been probed experimentally. Failure to determine the barrier in the experimental spectra in the case of one system is attributed to the chiral conformation of the global minimum. The rotational profile was established at the PM3 level and verified at the DFT level of theory. The solvent effect, the 0th-order vibrational corrections, and the temperature dependence of the Boltzman distribution of conformers and kinetic equilibrium are discussed.

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