COMPARISON OF CHEMICAL EXCHANGE RATES DETERMINED BY NMR LINE-SHAPE AND EQUILIBRATION METHODS: INTERNAL ROTATION OF N-METHYL-N-BENZYLFORMAMIDE,
Abstract
The rate of internal rotation about the C-N amide bond was studied in N-methyl-N-benzylformamide between 170 and 90C by an nmr complete line-shape analysis method and between 20 and -2.5C by an equilibration technique. Exchange rates were calculated from the nmr spectra of the benzyl and formyl protons in the two rotational isomers by treating them as two separate, uncoupled, exchanging AB systems with unequal populations. The calculations for the formyl protons required inclusion of temperature dependence in the chemical shift. The equilibration studies were performed on samples in which the isomer with the methyl cis to the formyl group was concentrated by complexing the equilibrium mixture with uranyl ion and stripping it off at low temperatures. The activation parameters obtained from the nmr studies agree well with those obtained by the classical equilibration method. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 18, 1967
- Accession Number
- AD0646873
Entities
People
- Herbert S. Gutowsky
- J. Jonas
- T. H. Siddall
Organizations
- University of Illinois Urbana–Champaign