NMR Spectra of Some Halogenated Propenes

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Abstract
The 40‐Mc/sec nuclear magnetic resonance (NMR) spectra of CF3CF=CF2, cis and trans isomers of CF3CCl=CFCl, and CF3CCl=CF2 have been analyzed in terms of the NMR parameters of the molecules; i.e., the magnetic shielding constants of the various fluorine nuclei and the spin‐spin coupling constants between them. The spectrum of perfluoropropylene, CF3CF=CF2, has been analyzed adequately by a first‐order perturbation treatment. The spectrum of each of the isomers of CF3CCl=CFCl has been analyzed exactly as an AB3 system of spins by the use of the trace relations only. In a previous analysis of the cis‐isomer, a small signal from the trans‐isomer was not identified. This small signal has now been proved to arise from the trans‐isomer. The spectrum of CF3CCl=CF2 has been analyzed by an interative scheme on an electronic computer. Here the nuclei were treated as an ABC3 system of spins. The various magnetic parameters determined by these analyses have been compared with the molecular structures and have been briefly discussed in terms of the theories of the magnetic properties of molecules.