1. NMR Determination of Hydrogen Bond Thermodynamics in a Simple Diamide: A Physical Chemistry Experiment
- Author
-
Massiel C. Stolla, Janine G. Morton, Sophia R. Koshland, Casey H. Londergan, Mark H. Schofield, and Candice L. Joe
- Subjects
chemistry.chemical_classification ,NMR spectra database ,Chemistry ,Hydrogen bond ,Intramolecular force ,Non-covalent interactions ,Molecule ,Physical chemistry ,General Chemistry ,Nuclear magnetic resonance spectroscopy ,Spectroscopy ,Equilibrium constant ,Education - Abstract
Variable temperature NMR spectroscopy is used to determine the ΔH° and ΔS° of hydrogen bond formation in a simple diamide. In this two- or three-day experiment, students synthesize N,N′-dimethylmalonamide, dimethylsuccinamide, dimethylglutaramide, or dimethyladipamide from methylamine and the corresponding diester (typically in 50% recrystallized yield) and record NMR spectra at temperatures between 200 and 313 K. Solutions of N-methylacetamide in concentrations between 1.00 mM and 13.1 M (neat) are prepared and their NMR spectra recorded to determine the chemical shift of the amide proton in the hydrogen-bonded (δB) and nonbonded (δN) limits. By using these data, the equilibrium constants, ΔH°, and ΔS° for the conversion of an open-chain diamide to a cyclic structure with an intramolecular hydrogen bond are determined.
- Published
- 2015
- Full Text
- View/download PDF