Methylene group, proton

The H NMR of isonarciclasine tetra-acetate [148] shows multiplets at <5 2-8 and 3-2 for the methylene group protons as does the model compound [149] of known stereochemistry. The all-c/s-acetate [150] does not show this type of absorption. (110)... 

The cyclic ether (25) has been prepared via the cyclization of 26 in monoglyme with potassium amide.14,15 The magnetic nonequivalence of the methylene group protons in 25 have been compared with other 1,2-disubstituted ferrocenes.16... 

The olefinic methylene group (protons and carbon) and the three methyl groups (protons and carbons) are trivial assignments, and they correspond with our previous discussion. Of more interest and of greater utility, we assign the three methine protons the doublet of doublets at 2.86 ppm (correlates with the carbon resonance at 63.0 ppm), the apparent quartet at 2.60 ppm (correlates with the carbon resonance at 48.0 ppm), and an apparent triplet at 1.76 ppm (correlates with the carbon resonance at 50.1 ppm). From the COSY and from the known structure, we now are now able to assign all three methine resonances and feed this information back into the COSY to establish other correlations. 

C-5 axial proton, which coincides in chemical shift with the C-6 methylene group protons, but the C-7-H signal is simplified in CDgCOgD solution because the axial C-5-H signal is shifted to lower field and no longer has the same chemical shift as the C-6 protons. In CDgCOgD solution the C-7-H signal can be analyzed from double resonance studies as a six-line multiplet [J g = H-8Hz + 7,6/s) =... 

FIGURE 4.28. Energy levels for the three spin states of the methylene group (protons a and b) that produce the triplet shown in Figure 4.27. 

As the experimental H-chemical shifts of the methylene group protons in allenes are related to the C-chemical shifts cy of the methylene carbon atoms (10), the corresponding proton and chemical shift parameters, m (R) and 7 (R), respectively, reflect similar physical effects. 

Introduction. All presently known organic synthesis applications of l-(methylthiomethyl)benzotriazole are based on the high acidity of the methylene group protons (and, thus, ready formation of a carbanion) and on the possibility of selective cleavage of benzotriazolyl or methylthio groups under a variety of conditions. 

In order to study the mobility of the methylene group protons of the 5(6)-(l-adamantyl)-2-phenoxymethylbenzimidazole (150) they have condensed compound 150 with benzaldehyde at 175-179°C and obtained the product 152 in 50% yield. 

In addition to the P spectra, Fig. 13 also illustrates the C and H spectra of the dystrophic and normal muscles. The multiple resonances in the C spectra represent only one class of compounds—neutral fats. The H spectra show two peaks, one from the repeating methylene group protons of fatty acids in neutral fats and another peak from the water protons. Dystrophic muscle contains more fat and less water than normal muscle. 

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