Methylene and methyl protons

TABLE B.1 Substituent Constants for Alkyl Methylene (and Methyl) Protons. 

Assignment of protons in side chains is also critical HCCH-COSY and HCCH-HOHAHA are widely used to facilitate these assignments. Because each amino acid has an asymmetric center, stereospecific assignments for methylene and methyl protons are obtained whenever feasible. 

Figure 15.7 Splitting patterns from methylene and methyl protons.

Table III. Chemical Shift Values of Methylene and Methyl Protons of Benzyl Derivatives of 2,6-Dimethylphenol (13)...

The temperature dependence of the substituent proton resonances in 1,1, 3,3, 5,5, 7,7 -octamethyl-, 35, mono-t-butyl-, 32, and 1,1 -di-t-butyluranocene, 33, are all linear. Similarly, both the methylene and methyl protons of 1,1 -dineopentyluranocene 31 are linear. For this case, the results imply a relatively fixed conformation with the t-butyl group swung away from the central uranium (conformation A in Figure 12 R=t-OBu). The non-linearity of the methyl protons of 1,1 -diethyluranocene 28 is interpreted as an effect of temperature on the populations of different conformations having different pseudo-contact shifts. Conformation A in Figure 12 (R=CH3) predominates but other conformations also contribute. We have no simple interpretation of the non-linearity of 1,1 -dimethyluranocene, 27, at this time. Some of the results are summarized in Table X. 

The UV/vis spectrum of carotenes usually shows three bands between 450 and 500 nm and an additional cis band around 330 nm, when there is a cis-con-figured double bond present (Isler, 1971). The H-NMR spectrum just shows ill-defined multiplets for methine, methylene, and methyl protons (Fig. 5.2.1)... 

Figure 3.37 The spectra of butylamine. The amine protons give rise to the sharp singlet at 1.1 ppm. The adjacent methylene protons are shifted to about 2.7 ppm by the electronegative nitrogen, while the other alkyl methylene and methyl protons appear at their usual chemical shift positions. (Reprinted with permission of Aldrich Chemical Co., Inc., modified by addition of the structure and peak identification.)...

Figure 1 High resolution 100 Mhz spectrum of PEO750 in a Graphon/carbon tetrachloride dispersion, showing both the methylene and methyl protons.

The product 2 was further characterized by multinuclear NMR spectroscopy. Homonuclear decoupling experiments show that the peaks at 2.4 and 0.74 ppm in the NMR spectrum are due to methylene and methyl protons on Ae nitrogen bound to boron, and the muMplets at 1.27 and 0.13 ate associated with methyl and methylene on aluminum. NMR spectrum reveals four main peaks at 37.8, 19.9,9.4, and -1.5 ppm. The shift correlation spectrum shows that... 

A study has been made of the diastereotopy of the methylene and methyl protons in ethyl and isopropyl esters of purine nucleoside uronates. Anisochromism of the diastereotopic protons was conditional upon both close spatial proximity and fixed orientation of the heterocycle vis-a-vis the alkoxycarbonyl group. 139 Unsaturated nucleoside uronates such as (89) have been prepared by p-elimination and their chirooptical properties investigated, i ... 

Figures 3 and 4 compare the 300 MHz spectra of isotactic poly(butene-l) and isotactic polystyrene with the spectra of partially deuterated analogs. The resonances of methine, methylene and methyl protons are adequately resolved in these spectra. An AB pattern is observed for the methylene proton resonances in Figure 3A, as expected, but is barely evident in Figure 4C, due to the fact that the methylene protons in polystyrene have very similar shifts.

Table 7.1 Comparison of calculated ((itheor) versus experimental (5exp) chemical shift values (ppm) for hydroxyl, methylene, and methyl protons of ethanol [see, e.g., I. Weinberg and J. R. Zimmerman, J. Chem. Phys. 23, 748, 1955]. Conformationally averaged theoretical methyl-proton values are given for comparison with experiment.

The values shown in Table 7.2 cannot be directly compared with experimental liquid values, because the latter involve Boltzmann-weighted averaging over torsional motions that are rapid on the NMR time scale. However, for the coupling J[CH2,CH3] between methylene and methyl protons one can make an eyeball estimate by simply averaging the six vicinal couplings between methylene protons H(5), H(8) and methyl protons H(6), H(7), H(9), leading to the following... 

The chemical shifts of the methine protons are also shifted downfield in the m isomer because they are deshielded by the aromatic rings. The coupling patterns for the methine protons are similar in both of these spectra they have similar vicinal couplings to both the methylene and methyl protons. In theory, they should appear as quartets (split by coupling to the vicinal methyl protons) with each line in the quartet split to a triplet (by the two central methylene protons). However, since the methine protons have similar vicinal couplings to methyl and methylene protons (coupling to n = 5 similar atoms), six (n + 1) lines are observed for the methines. 

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