Conformational Isomerism of 3‑Chalcogenomethyl‑N‑Methyl-2-Pyrrolidinones: Insights from NMR Spectroscopy and Molecular Modeling
A conformational analysis of N-methyl-2-pyrrolidinone 3-substituted by methoxyl, thiomethoxyl, and selenomethoxyl is reported by means of 1H nuclear magnetic resonance spectroscopy and electronic structure calculations. The five-membered ring has an envelope conformation with the α-carbonyl substitu...
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Veröffentlicht in: | The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2020-10, Vol.124 (41), p.8509-8518 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | A conformational analysis of N-methyl-2-pyrrolidinone 3-substituted by methoxyl, thiomethoxyl, and selenomethoxyl is reported by means of 1H nuclear magnetic resonance spectroscopy and electronic structure calculations. The five-membered ring has an envelope conformation with the α-carbonyl substituent being able to assume two positions: pseudo-axial and pseudo-equatorial. In vacuum, the calculations pointed to the pseudo-axial conformer as the most stable one, and this preference increases with the size of the substituent and a decrease in its electronegativity. Natural bond orbital analysis evidenced the importance of electron delocalization on the stability, and a principal component of analysis (PCA) plot of the hyperconjugative interactions revealed the main ones. Steric and electrostatic effects were also investigated by energy decomposition analysis. |
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ISSN: | 1089-5639 1520-5215 |
DOI: | 10.1021/acs.jpca.0c06679 |