Carbon coupling constants three-bond

Conformational analysis of oligosaccharides in solution by NMR spectroscopy is based on the study of chemical shifts, n.O.e. s, and three-bond, proton-carbon coupling constants. Generally, the experimental NMR parameters P. . , (such as n.O.e. s or... 

Until now, the determination of three-dimensional structures of oligosaccharides in solution was based primarily on proton-proton distance information obtained from n.O.e. data. Here, we discuss the application of three-bond proton-carbon coupling constants. 

Three-Bond Proton-Carbon Coupling Constants. Routine applications of the three-bond C-O-C-H proton-carbon coupling constants ( Jpu) have been coiqplicated by experimental difficulties involved in tneir measurement using classical H-coupled NMR spectroscopy and a limited knowledge of the angular dependence of for the C-O-C-H... 

F7g. 2.49. INADEQUATE spectra of the 13C—UC doublets of piperidine (neat liquid. 50 MHz), including an analysis of one-, two-and three-bond carbon-carbon coupling constants [58]. 

Two-bond carbon-carbon coupling constants (2JCC) are usually smaller than three-bond couplings (3JCC), as shown for hexanoic and (E)-2-hexenoic acid ... 

Figure 4.11. The application of selective proton decoupling in the measurement of heteronuclear long-range proton-carbon coupling constants. Lower traces are from the fully proton-coupled carbon-13 spectrum and the upper traces from that in which the methyl ester protons of 4.3 were selectively decoupled to reveal the three-bond coupling of the carbonyl carbon across the alkene.

The one-dimensional INADEQUATE experiment was in fact the original version and was proposed as a means of measuring carbon-carbon coupling constants [81]. The use of double-quantum filtration removes the parent resonances that dominate the spectrum and mask the desired splittings, especially when smaller two- and three-bond... 

As indicated, the magnitudes of three-bond F—F and F—H coupling constants are observed to vary as a function of the sum of the electronegativities of the other substituents that are on the two carbons in question, with the absolute values of these coupling constants... 

Carbon and Proton NMR Data. Some typical carbon and proton chemical shift and coupling constant data for fluorothiophenes are given in Scheme 3.70. Note that the two-, three-, and four-bond F—C... 

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