1H and 13C NMR spectroscopy

Hu, Y., Heshimoto, H., Moie, G., Hengartner, U., and Koyama, Y. 1997. Unique properties of the ll-cis and 11,11 -di-civ isomers of P-carotene as revealed by electronic absorption, resonance Raman and 1H and 13C NMR spectroscopy and by HPLC analysis of their thermal isomerization. J. Chem. Soc. Perkin Trans. 2 2699-2710. 

The very first report on the use of ionic liquids as soluble supports was presented by Fraga-Dubreuil and Bazureau in 2001 [102]. The efficacy of a microwave-induced solvent-free Knoevenagel condensation of a formyl group on the ionic liquid (IL) phase with malonate derivatives (E1CH2E2) catalyzed by 2 mol% of piperidine was studied (Scheme 7.89). The progress of the reaction could be easily monitored by 1H and 13C NMR spectroscopy, and the final products could be cleaved from the IL... 

C isotope Diamond entries Graphite entries 1H- and 13C-nmr spectroscopy Low carbon silicomanganese ... 

Platinum-195-NMR spectroscopy is a useful means to prove isomerization of the HH and HT isomers of Pt(2.0+)2. Both 1H- and 13C-NMR spectroscopies may also be used to examine isomerization (59, 67) however, quite often these are not useful enough because of the overlap of peaks for both isomers and difficulty in assignment. The large... 

In a subsequent paper22 the Plesnicar group extended these studies to two different substrates, cumene and triphenylmethane. However, while newly obtained HOOOH l70 NMR spectra confirmed the previous results, it was impossible to obtain the l70 NMR spectra of cumene and triphenylmethane hydrotrioxides. This was ascribed, by the authors, most probably to too large a line-width, due to the internal asymmetry of these derivatives, which prevented their observation. The derivatives were, in any case, characterized by 1H and 13C NMR spectroscopy. 

Modem analytical techniques have been developed for complete characterization and evaluation of a wide variety of sulfonic acids and sulfonates. The analytical methods for free sulfonic acids and sulfonate salts have been compiled (28). Titration is the most straightforward method of evaluating sulfonic acids produced on either a laboratory or an industrial scale (29,30). Spectroscopic methods for sulfonic acid analysis include ultraviolet spectroscopy, infrared spectroscopy, and 1H and 13C nmr spectroscopy (31). Chromatographic separation techniques, such as gc and gc/ms, are not used for free... 

The formation of such materials may be monitored by several techniques. One of the most useful methods is 1H- and 13C-nmr spectroscopy where stable complexes in solution may give rise to characteristic shifts of signals relative to the uncomplexed species (43). Solution nmr spectroscopy has also been used to detect the presence of solid inclusion compound (after dissolution) and to determine composition (host guest ratio) of the material. Infrared spectroscopy (126) and combustion analysis are further methods to study inclusion formation. For general screening purposes of solid inclusion structures, the x-ray powder diffraction method is suitable (123). However, if detailed structures are required, the single crystal x-ray diffraction method (127) has to be used. 

Bridgehead bicyclo[4.4.0]decyl, bicyclo[4.3.0]nonyl, and bicyclo[3.3.0]octyl cations are found to be rapid equilibrating ions (see Section 3.5.2.1).188 The isomeric bridgehead congressane (diamantane) cations 52 and 53 have been prepared and observed.182 The diamant-4-yl cation 52 rapidly rearranges to the diamant-l-yl cation 53 at —60°C, possibly through intermolecular hydride shifts. Bridgehead bicyclo[3.3.3]undec-l-yl cation 54 has also been observed by 1H and 13C NMR spectroscopy.189... 

Cycloalkadienyl cations, particularly cyclohexadienyl cations (benzenium ions), the intermediate of electrophilic aromatic substitution, frequently show remarkable stability. Protonated arenes can be readily obtained from aromatic hydrocarbons244 251 in superacids and studied by 1H and 13C NMR spectroscopy.252,253 Olah et al.252 have even prepared and studied the parent benzenium ion (C6H7+) 88. Representative 1H NMR spectra of benzenium253 and naphthalenium ions25488 and 89 are shown in Figures 3.11 and 3.12, respectively. 

Likewise, the reaction of bromo- and iodoarenes with ethyl fluoroantimonate in S02 gave the corresponding ethylarylhalonium ions. The structures of all aklylar-ylhalonium ions prepared have been characterized by 1H and 13C NMR spectroscopy. 

Similarly, a variety of dimethylethylene, trimethylethylene, and tetramethylethy-lene halonium ions have been prepared and studied by 1H and 13C NMR spectroscopy.99 386 389 Some of the representative examples are ions 163-166. 

Similarly, several 2- and 2,5-substituted tetramethylenehalonium ions (174-178) have been prepared and studied by both 1H and 13C NMR spectroscopy.99 410 411... 

Superelectrophilic dications 50 have been observed by Coustard,197 who used 1H and 13C NMR spectroscopy in triflic acid at low temperature (Scheme 5.25). They... 

Preparation Of Oxacycloalkanes. Unsaturated alcohols can be cyclized under superacid conditions to yield oxolane derivatives. Laali et al.685 have studied the protonation of homoallylic adamantylideneadamantyl alcohols. The pseudo-axial alcohol 157 was protonated in HSO3F-SCUOF to give the intermediate protonated cyclic ether observed by 1H and 13C NMR spectroscopy, which, upon quenching, furnished the corresponding ether [Eq. (5.243)]. 

As demonstrated in previous publications, model reactions of L-proline and monosaccharides result in complex mixtures of proline specific compounds (J —4 ) During the Maillard reaction of L-proline and reducing sugars more than 120 proline specific compounds were identified by MS-, IR-, 1H- and 13c-NMR-spectroscopy (among them ... 

In general solutions of azines in liquid ammonia are homogeneous, making it possible to detect by 1H- and 13C-NMR spectroscopy the occurrence of intermediary compounds (see Section IV). In case of 3-nitropyridine the NMR spectrum in liquid ammonia did not feature any indication for intermediary covalent er-adducts. 

The relative and predominant conformations of diastereomeric 14-hydroxy-( )-homoeburnanes 16 have been established by 1H- and 13C-NMR spectroscopy, indicating that previous assignments of C-12 and C-20 signals of trans-(D/E)-ring fused vinca alkaloids must be reversed (85JCS(P2)1319). 

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