Propenal Proton decoupling

Since the NMR resonances of chemically different protons are more widely separated at higher field, X3C-NMR spectra measured without proton decoupling will have more clearly defined multiplets, and as a result the magnitudes of proton-carbon coupling constants will be more easily extracted. A good illustration of this aspect is the proton-coupled spectra of propene recorded at 25 and 101 MHz discussed by Dubs and von Phil-ipsbom (7). 

A more recent demonstration of the usefulness of high resolution deuterliim NMR as an analytical technique Is Illustrated In Figure 5. Here deuterltim resonances were used to characterize the radical- and cation-derived products obtained by anodic oxlda tion of the [2,2-d2] butyrate Ion ( ). The assignment of these resonances was made on the basis of the 1 1 relationship between the chemical shifts of and H, and the deuterium label distribution was determined from the proton noise-decoupled NMR spectra. As can be seen from Figure 5, propene was labeled In the terminal olefinic carbon but not in the central olefinlc carbon atom, while propane turned out to be deuterium-labeled exclusively at Cj. 

Figure 5. a, NMR spectra (at 100 MHz, in CCI under pressure) of a mixture of gaseous propane, propene, and cyclopropane, b, Proton noise-decoupled NMR spectra (at 15.4 MHz, in CCl under pressure) of some of the reaction products obtained from the electrolysis of the [2,2-d,] butyrate ion Expansion, proton-coupled deuterium resonances. (Reproduced from Ref. 6. Copyright 1980, American Chemical Society.)... 

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