Variable Temperature NMR Experiment Studying Restricted Bond Rotation

Michael T. Huggins; Tanay Kesharwani; Jonathan Buttrick; Christopher Nicholson

doi:10.1021/acs.jchemed.0c00057

Variable Temperature NMR Experiment Studying Restricted Bond Rotation

Michael T. Huggins, Tanay Kesharwani, Jonathan Buttrick, Christopher Nicholson

Biochemistry, Chemistry & Physics

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

30 Scopus citations

Abstract

Nuclear magnetic resonance (NMR) spectroscopy has become a cornerstone tool for studying a variety of molecular features in advanced chemistry laboratories. In this experiment, students prepare a pyrrole-β-amide via a one-pot, three-step synthesis and use NMR spectroscopy to confirm its molecular structure. In addition, variable temperature (VT) ¹H NMR spectroscopy is used to study the dynamic amide bond, a functional group with restricted rotation about the C-N bond. The VT NMR data allow the students to determine the coalescence temperature associated with the slow equilibrium at room temperature and the corresponding energy barrier (ΔG^&daggar;) for the restricted rotation about the C-N bond.

Original language	English
Pages (from-to)	1425-1429
Number of pages	5
Journal	Journal of Chemical Education
Volume	97
Issue number	5
DOIs	https://doi.org/10.1021/acs.jchemed.0c00057
State	Published - May 12 2020

Keywords

Amides
Conformational Analysis
Hands-On Learning/Manipulatives
Laboratory Instruction
NMR Spectroscopy
Organic Chemistry
Upper-Division Undergraduate

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10.1021/acs.jchemed.0c00057

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abstract = "Nuclear magnetic resonance (NMR) spectroscopy has become a cornerstone tool for studying a variety of molecular features in advanced chemistry laboratories. In this experiment, students prepare a pyrrole-β-amide via a one-pot, three-step synthesis and use NMR spectroscopy to confirm its molecular structure. In addition, variable temperature (VT) 1H NMR spectroscopy is used to study the dynamic amide bond, a functional group with restricted rotation about the C-N bond. The VT NMR data allow the students to determine the coalescence temperature associated with the slow equilibrium at room temperature and the corresponding energy barrier (ΔG&daggar;) for the restricted rotation about the C-N bond.",

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KW - Conformational Analysis

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Variable Temperature NMR Experiment Studying Restricted Bond Rotation

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