B. L. Shapiro, H.-L. Lin, M. D. Johnston
Feb 1, 1973
Citations
0
Influential Citations
6
Citations
Journal
Journal of Magnetic Resonance
Abstract
Abstract The compounds 1,1,1-trifluoroacetone,1,1,1,3-tetrafluoroacetone,1,1,1-trifluoro-3-chloroacetone, 1,1,1-trifluoro-3-bromoacetone, 1,1,1-trifluoro-3,3-dibromoacetone, 1-fluoro-l-chloroacetone, 1-fluoro-3-chloroacetone, and 3-fluorobutan-2-one were prepared and solvent effects on their NMR parameters, as well as those of pentafluoroacetone, were investigated. The NMR parameters discussed are the proton and fluorine chemical shifts and the 2 J HF , 3 J HH , 3 J HF , 4 J HF , and 4JFF, where available. It was found that the proton chemical shift and the 2JHF and 4JHF give the most valuable structural information, at least qualitatively. Fluorine chemical shifts, because of the importance of the paramagnetic term in their shift Hamiltonian, failed to give easily understood correlations with conformation. A variable temperature study of the proton chemical shifts of all but the first of the compounds listed above was carried out to ascertain the relative populations of the stable conformers of these molecules and to obtain the chemical shifts of the isolated conformers along with the thermodynamic parameters of the interconversion. From the obtained populations, the 4JHF of the isolated conformers were obtained.