Applications of Proton NMR

The most impv rtant chemical applications of proton NMR Spectroscopy have been to the identification and smictural elucidation of organic, metal-organic, and hiocheniical molecules. In addition, how cvcr, the method is often u.selul for quaiiliiative determination (vf absorbing. species. 

The proton N.MR speciruni shown in figure 19-24 is for an oiganic compouml h.tvmg the empirical formula ( M, 0- Identilv the compountl. 

The empirical formula and (he 2 2 . distribuiion of the remaining [)roions indicate the presence of an i-propy group a.s well. The structure 

FIGURE 19-24 NMR spectrum and peak integral curve for the organic compound CsHioOp in CCI4. (From R. M. Silverslein, G. C. Bassler, and T, C. Morrill. Spectrometnc Identification of Organic Compounds, 3rd ed., p, 296, New York Wiley. 1974. With permission.) 

FIGURE 19-25 NMR specira for Iwo organic isomers in CDClj, (Courtesy of Varian Inc., Palo Alto, CA.) 

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In most cases, the IL under investigation is not available in deuterated form. This of course limits the applicability of proton NMR. One (expensive) solution to this problem can be the synthesis of a deuterated version of the particular IL ([3] and references therein). Other solutions to this problem will be discussed in Sect. 5. 

One of the more recent applications of proton NMR in solid polymers has been the use of multiple quantum coherence (MQCOH), which is developed among clusters of dipolar coupled protons vide infra) to infer details of chain dynamics [20], and (which is another way of making the same statement) local dipolar couplings [21]. 

A Theory of NMR 499 19B Environmental Effects on NMR Spectra 510 19C NMR Spectrometers 521 19D Applications of Proton NMR 526 19E Carbon-13 NMR 529 19F Application of NMR to Other Nuclei 533 19G Multiple Pulse and Multidimensional NMR 534... 

By application of proton multiple quantum (MQ) NMR experiments, information about the segmental order parameter, which is directly related to the restrictions on chain motion (cross-links) formed upon gelation of PVA, is obtained.103The quantitative study of rigid phase... 

Since about 1960 nuclear magnetic resonance (NMR) spectroscopy has become an important tool for the study of chain configuration, sequence distribution and microstructure of polymers. Its use started from early broad-line studies of the one-set of molecular motion in solid polymers and passed through the solution studies of proton NMR, to the application of the more difficult but more powerful carbon-13 NMR methods to both liquids and solids. 

There have been several initial applications of the NMR method to the study of solids of catalytic interest. Selwood and co-workers (14) have measured proton relaxation times (Ti) of water-soaked 7-aluminas containing iron oxide, copper oxide, and chromium oxide. 

Some other examples of application of 15N NMR spectroscopy include establishing the protonation site of A2-pyrazolines (87MI301-01) and assigning the structures to isomeric N-7 and N-9 substituted purines (86T5073). 

Various applications of 13C NMR spectroscopy have been made examples include analysis of the spectra of substituted thieno[2,3-6 ]thiophenes (76ACS(B)417> and studies of the relaxation of both proton and 13C nuclei (80JMR(40)197>. The 13C spectra of thiophenium salts have been examined and, again, a strong downfield shift of the 0 -carbon atoms is seen, indicative of considerable charge transfer from sulfur to the 0 -positions (74TL75). 

Although proton spectra are not very useful for identification purposes, 13C nmr spectra are very useful. Chain-branching and ring-substitution normally cause quite large chemical-shift changes, and it is not uncommon to observe 13C shifts in cycloalkanes spanning 35 ppm. Some special features of application of 13C nmr spectra to conformational analysis of cycloalkanes are described in Section 12-3D. 

Another application of LC-NMR in natural products chemistry concerns biosynthetic studies employing feeding experiments with stable isotope-labelled compounds. H NMR spectra allow the determination of the amount of isotopic label incorporated into metabolites, e.g. by observing signals that arise from /-couplings of protons to 13C-labelled nuclei [41,42],... 

Most of the normally encountered applications of proton and carbon NMR spectroscopy have been applied in studies of vanadate complexes, complexation reactions, equilibria, and kinetics. Carbon-13 studies of the influence of complexation... 

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