13C NMR spectrometry

Nuclear magnetic resonance (NMR) spectrometry has seldom been used as a quantitative analytical method but can have some practical importance in the characterization of surfactants [296-298]. 13C-NMR spectrometry has been used for the qualitative and also quantitative analysis of dodecyl, tetradecyl, and cetyl sulfates [299]. H- and, 3C-NMR spectra of sodium dodecyl sulfate are given by Mazumdar [300]. 

Cd (and Hg) complexes with bis- and tris(l-pyrazolyl)methanes and -ethanes, as well as with bis(l-triazolyl)methane, have been prepared and studied by conductance measurements (H20, dmso, and dimethylformamide (dmf) solutions), IR, far-IR, H, and 13C NMR spectrometries.203 The Cd halides form complexes of the type [CdLX2] complexes of the types [CdL2](C104)2 and [CdL3](BF4)2 are obtained from the respective Cd salts. 

The reactions of mercury(II) salts with oligo-amines afford informative examples for the fact that counterions induce the formation of a distinct complex or select a distinct complex in an equilibrium to crystallize with. Thus, Hg11 acetate with dien under exactly the same reaction conditions, in the presence of C104- or PF6-, yields the dinuclear complex [Hg2(dien)3](C104)4 or the mononuclear species [Hg(dien)(H20)](PF6)2, respectively, both characterized by IR, H, and 13C NMR spectrometries, by fast-atom bombardment (FAB) MS, cyclovoltammetry, and X-ray structure analyses.209 In the first compound Pna2, Z = 4), one Hg adopts five-coordination with one tridentate and one bidentate dien ligand, which with the remaining N-donor binds to the... 

All poly(3HB-co-3HV)s synthesized by R. europha that were characterized for sequence distribution were found to be random copolymers as indicated by 13C NMR spectrometry. However, as noted above, the fractionation of some poly(3HB-co-3HV) copolymers revealed that the sequence distributions determined by 13C NMR might not be reliable. In that study, poly(3HB) that had a chad sequence indicative of a random poly(3HB-co-3HV), as determined by 13C NMR, was fractionated into various copolymers that had significantly different compositions. 

Clark et al. [53] used 13C NMR spectrometry to study the metabolism of primaquine by microorganism. A total of 77 microorganisms were evaluated for their ability to metabolize primaquine. Of these, 23 were fund to convert primaquine to one or more metabolites as studied by thin-layer chromatography analysis. Preparative scale fermentation of primaquine with four different microorganisms resulted in the isolation of two metabolites identified as 8-(4-acetamido-l-methylbutylamino)-6-methoxyquinoline and 8-[3-carboxy-l-methylpropyl amino]-6-methoxyquinoline. The structures of the two metabolites were proposed primarily on a comparison of the 13C NMR spectra of the first metabolite and the methyl ester of the second metabolite with that of primaquine. The structures of both metabolites were confirmed by direct comparison with authentic samples. 

For pedagogical and practical reasons, this chapter treats only protons. 13C NMR spectrometry is treated in Chapter 5, and other useful nuclei are treated in Chapter 7. Chapter 6 is devoted to 2-D NMR. 

Aromatic carbon content cannot be directly determined from 13C NMR spectrometry because it overlaps with olefinic carbon. Aromatic and olefinic hydrogens can be resolved in H NMR spectrometry, but the chemical shifts of methine hydrogens on esters of secondary alcohols overlap with chemical shifts of olefinic hydrogen in the NMR spectra of fulvic acids. The ring content (0) is a difference determination between the index of hydrogen... 

Ofloxacin was characterized by UV, vibrational, IR spectroscopies, 1H-, 13C-NMR spectrometry, X-ray powder diffraction pattern, single crystal X-ray diffraction, and mass spectrometry (09MI3). Levofloxacin formed a supramolecular complex with p-cyclodextrin at a molar ratio of 1 1, which was characterized by using UV, fluorescent spectra, DSC, and X-ray diffraction (07MI68). 

Hedges, J. I., P. G. Hatcher, J. R. Ertel, and K. J. Meyers-Sculte. 1992. A comparison of dissolved humic substances from seawater with Amazon River counterparts by 13C-NMR spectrometry. Geochimica et Cosmochimica Acta 56 1753—1757. 

In short, Zc and Utotal provide powerful, rigorous constraints on the interpretation of other analytical data from 13C NMR spectrometry or ultra-high-resolution mass spectrometry, which must ultimately be reconciled with the bulk chemistry of a sample of DOM. Calculations of Zc and f7total for bulk samples of DOM are only possible if elemental analyses for H and O are performed. This is a strong incentive for developing methods to more readily obtain suitable dry, ash-free samples of marine DOM. 

Gas-phase ozonolysis has only recently been able to prove the existence of terpenic ozonides by 13C NMR spectrometry, thanks to characteristic peaks in the 100-120 ppm range. 

However, a search for similar products in field isolates of M. tuberculosis proved fruitless. The work instead focused on a family of simple acylated trehaloses first reported by Minnikin et al.61 The structures of these acylated trehaloses were elucidated by a combination of GC-MS and H-13C-NMR spectrometry.68... 

Samples for 13C NMR spectrometry are usually dissolved in CDC13, and the 13C peak of tetramethylsilane (TMS) is used as the internal reference. A list of the common deuterated solvents is given in Appendix A. 

C-NMR spectrometry has assumed a very efficient role in the determination of the structure and stereochemistry of Nuphar alkaloids and their derivatives. Accurate assignments of chemical shift values to particular carbon atoms in the molecules and clear changes in chemical shift values of particular carbon atoms, owing to conformational transformations, are well within the rules generally accepted for I3C-NMR spectroscopy, which facilitates identification of the signals in the l3C-NMR spectra. 

The pseudo-double bond character of amides is much more pronounced than for esters due to the conjugation of the H-N-C=0 moiety and is correlated to the ability of distorted amides to be hydrolyzed to bases [19]. For this reason, the barrier to interconversion is significantly higher that for the ester series, with AGl typically ranging from 16 to 22 kcal mol-1 [17]. However, the rotational barrier is not solely due to conjugation and also partly arises from the orientation of the nitrogen lone pair which is perpendicular to the amide plane [20]. Therefore, the rates of isomerization are considerably slower than for esters. This means that both isomers can be observed by simple techniques, for example at room temperature by H and 13C NMR spectrometry and UV spectrophotometry [21]. 

Another set of tribenzotriquinacenes functionalized at the peripheral bridgehead positions is shown in Scheme 32. The triamines 162 and 163 were obtained in excellent yield by aminolysis of the methyltribenzotriquinacene 142 with ammonia and dimethylamine, respectively, in benzene solution [100]. Solvolysis of 142 in the neat alkyl (R = Me, Et, Pr, nBu) and benzyl mercaptane gave the three-fold thioethers 164 and 165 [106]. Oxidation of these compounds with raeta-chloroperbenzoic acid (MCPBA) led to complete decomposition [98], whereas use of dimethyldioxirane gave high yields of the tris(sulfones) 166 and 167 as thermally stable compounds [106]. 1H- and 13C-NMR spectrometry as well as X-ray structural analysis revealed the dynamic behaviour of the sulfones,... 

C NMR spectrometry is also very helpful in assignment of stereochemistry at C-25 (R/S) of spirostane type steroidal saponins and sapo-genins. Agarwal et al. (138) have studied in detail the carbon resonances of smilagenin and sarsasapogenin using DEPT, COSY, TOCSY, HETCOR,... 

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