H Spectra

Because the digitized areas of the H spectrum give the relative number of pro tons responsible for each signal HETCOR serves as an alternative to DEPT for count mg the number of protons bonded to each carbon... 

Although the ID H spectrum of 2-hexanone is simple enough to be interpreted directly, you can see that COSY offers one more tool we can call on in more complicated cases. 

Figure 2.17 Application of the reverse DEPT pulse sequence to monitor C-labeled glucose by mouse liver-cell extract. (A) Normal FT spectrum. (B) Reverse DEPT spectrum showing the a- and )3-anomeric proton resonances. (C) Two different CH2 proton resonances, a and b, appear after 1.5 h of metabolism. (D) Edited H spectrum confirming that the CH2 resonances arise from metabolic products. (Reprinted from J. Magn. Resonance 56, Brooks et al., 521, copyright 1984, Academic Press.)...

MHz, solvent CDC13 H spectrum and homodecoupling spectra Determination of the coupling constants... 

There is no noticeable four-bond coupling between the CF3 fluorines and the CH2 group of l,l,l-trifluoro-2-butanone, as can be seen in the H spectrum of this compound given in Fig. 5.7. 

FIGURE 58-2 Hydrogen ( H) spectrum from a normal human brain at 4 Tesla field strength. The spectrum is very complicated, comprised of many overlapping peaks which are difficult to resolve from each other. Spectral analysis routines make use of spectral models which are constructed from the individual spectra acquired from each biomolecule from in vitro solutions. This model is then fitted to the raw data and approximate concentrations for each biomolecule are extracted... 

Figure 3.19 H spectrum of the complex trani,-MeBrPt(PMe2R)2. (Adapted with permission of Nelson Thornes Ltd. from Figure 3.13 of Akitt, J. W. NMR and Chemistry, 3rd ed., 1992.)...

A systematic investigation of the free amino acids of the Leguminosae led to the isolation of a novel ninhydrin-positive compound from the leaves of Derris elliptica Benth. (Papilionidae) (93). This substance was analyzed as C6H,3N04 (microanalysis and high resolution mass spectrometry) and was shown to be an amino alcohol. The absence of a carbonyl in the 1R, the loss of 31 mass units in the mass spectrum, and a positive periodate cleavage reaction were best embodied into a dihydroxydihydroxymethylpyrrolidine structure. The relative simplicity of the NMR spectra (three peaks in the 13C spectrum four spin-system in the H spectrum) pointed out a symmetrical structure. Inasmuch as the material was optically active ([a]D 56.4, c = 7, H20), meso structures were ruled out, and the 2R, 3R, 4R, 5R relative configuration was retained (93). This structure (53) was further confirmed by an X-ray determination (94). 

Figure 8.3 Illustration of HR-MAS techniques applied to a resin-bound trisaccharide (a) static XH spectrum of the solvent swollen sample (b) XH spectrum with magic-angle spinning at 3.5 kHz (c) H spectrum with MAS and spin echo pulse sequence.

The power of the HR-MAS method for on-resin analysis has been further underscored in the development of new linkers. Without this method, only indirect analytical data after removal from the resin was available. Direct assessment of the resin-bound linker greatly facilitated the introduction of a 4,5-dibromo octane- 1,8-diol linker that was converted into an octane-1,8-diol linker cleavable by olefin metathesis at the end of the synthesis.6 The disappearance and reappearance of the olefinic protons as well as the growing oligosaccharide chain was clearly visible in the H spectrum (Fig. 8.7).7... 

Fig. 17.8 Intermolecular NOEs between [13CH3-Met, Phe-ds]-labeled cardiac troponin C and the drug bepridil (left panels, drug protein 1.5 1 right panels, 3.5 1). A, D methyl region of the H spectrum B, E HSQC spectra showing the 13CH3-Met signals of the protein C, F section from the NOESY spectrum with 13C-editing in one dimen-...

Fig. 8.10. H spectrum of toluene. Solely the molecular ion and its isotopomer are observed. (The CID spectmm of field-ionized toluene is shown in Chap. 2.12.1, the El spectrum is...

The splitting patterns of the protons in the aromatie region of the H spectrum are frequently used to establish the substitution pattern of an aromatic ring. For example, a trisubstituted aromatic ring has 3 remaining protons. There are 3 possible arrangements for the 3 protons - they can have relative positions 1,2,3- 1,2,4- or 1,3,5- and each has a characteristic splitting pattern. 

Figure 6.43 H spectrum of diclofenac glucuronide obtained after single trapping from a 100 pi injection of female urine 4 h after dosage of 50 mg of diclofenac. The spectrum was recorded using a cryogenic flow probe at 600 MHz. The spectrum indicates that the sensitivity is sufficient to run aU two-dimensional experiments needed for structure elucidation. Reproduced from [82] with permission from Elsevier.

Prior knowledge of the type of problem to be solved. For example, if aromatic substitution is suspected in an impurity then the couphng pattern of aromatic protons in a one-dimensional H spectrum is sufficient to distinguish the possible isomers. 

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