Predicted Reversal in N-Methylazepine/N-Methyl-7-azanorcaradiene Equilibrium Upon Formation of Their N-Oxides

René Fournier; Alexa R Green; Arthur Greenberg; Edward Lee-Ruff; Joel F Liebman; Anita Rágyanszki

doi:10.3390/molecules25204767

Predicted Reversal in N-Methylazepine/N-Methyl-7-azanorcaradiene Equilibrium Upon Formation of Their N-Oxides

Molecules. 2020 Oct 16;25(20):4767. doi: 10.3390/molecules25204767.

Authors

René Fournier¹, Alexa R Green², Arthur Greenberg², Edward Lee-Ruff¹, Joel F Liebman³, Anita Rágyanszki⁴

Affiliations

¹ Department of Chemistry, York University, Keele Campus, Toronto, ON MJ3 1P3, Canada.
² Department of Chemistry, University of New Hampshire, Durham, NH 03824, USA.
³ Department of Chemistry and Biochemistry, University of Maryland Baltimore County, Baltimore, MD 21250, USA.
⁴ Department of Physics and Astronomy, York University, Keele Campus, Toronto, ON MJ3 1P3, Canada;.

Abstract

Density functional calculations and up to five different basis sets have been applied to the exploration of the structural, enthalpy and free energy changes upon conversion of the azepine to the corresponding N-oxide. Although it is well known that azepines are typically much more stable than their 7-azanorcaradiene valence isomers, the stabilities are reversed for the corresponding N-oxides. Structural, thermochemical as well as nucleus-independent chemical shift (NICS) criteria are employed to probe the potential aromaticity, antiaromaticity and nonaromaticity of N-methylazepine, its 7-azanorcaradiene valence isomer. For the sake of comparison, analogous studies are performed on N-methylpyrrole and its N-oxide.

Keywords: DFT calculations; N-Methyl-7-azanorcaradiene; N-methylazepine; N-methylpyrrole; NICS; amine N-oxides; antiaromaticity; aromaticity.

MeSH terms

Azepines / chemistry*
Isomerism
Models, Molecular
Oxides / chemistry*
Quantum Theory
Thermodynamics*

Substances

Azepines
Oxides