HINDERED INTERNAL ROTATION IN BORON HALIDE COMPLEXES OF N,N-DIMETHYLFORMAMIDE
- 1 August 1965
- journal article
- Published by Canadian Science Publishing in Canadian Journal of Chemistry
- Vol. 43 (8), 2135-2140
- https://doi.org/10.1139/v65-288
Abstract
The barriers to internal rotation about the CN partial double bond in N,N-dimethyl-formamide (DMF) and its complex with BF3 have been determined in tetrachloroethane (TCE) by nuclear magnetic resonance measurements. The activation energy for rotation Ea, increased from 6.2 ± 0.3 kcal mole−1 for DMF to 14.5 ± 1.1kcal mole−1 for DMF•BF3. Values of ΔH≠ and ΔS≠ were also derived. Low field shifts of the methyl resonances and an increase in the relative shifts between the two methyl groups were observed on complex formation. The formyl coupling constant to the methyl groups was larger for the complex than for pure DMF. In addition, for DMF—BCl3 evidence for the presence of two types of complex was found. The present results are compatible with BF3 and BCl3 complexing to the amide oxygen atom. The energy changes for internal rotation and J variation are attributed to changes in the π character of the CN bond due to stabilization of the charged resonance from [Formula: see text] upon complex formation.Keywords
This publication has 9 references indexed in Scilit:
- Proton-proton double resonance studies of formamide-15N and N-methylformamide-15NMolecular Physics, 1964
- A PROTON MAGNETIC RESONANCE STUDY OF HINDERED INTERNAL ROTATION IN SOME SUBSTITUTED N,N-DIMETHYLAMIDES1The Journal of Physical Chemistry, 1962
- The analysis of the double resonance spectrum of N-methylformamideJournal of Molecular Spectroscopy, 1962
- Molecular Addition Compounds of Boron. V. Proton Chemical Shifts and the Stability of Adducts1,2Journal of the American Chemical Society, 1961
- N.M.R. SPECTRA OF SOME α–β UNSATURATED ESTERSCanadian Journal of Chemistry, 1961
- Nuclear Magnetic Shielding of Protons in Amides and the Magnetic Anisotropy of the C—O BondThe Journal of Physical Chemistry, 1959
- Valence-Bond Interpretation of Electron-Coupled Nuclear Spin Interactions; Application to MethaneThe Journal of Chemical Physics, 1959
- Negative Nuclear Spin-Spin Coupling Constants for Aromatic ProtonsThe Journal of Chemical Physics, 1959
- The Mode of Protonation of AmidesProceedings of the National Academy of Sciences, 1958