CPMAS NMR spectroscopy

The discovery, by the combined use of crystallography and CPMAS NMR, of the dynamic properties of 3,5-dimethylpyrazole (a trimer like (55)) in the solid state opened a new field of research 85JA5290,92JA9657). Other cyclic structures, dimers like (54) and tetramers like (56) were discovered 94JHC695 . At the beginning, only C CPMAS was used but afterwards N CPMAS (with labeled derivatives) proved to be superior. 

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Ahmad R, Kookana R, Alston A, Skjestad J (2001) The nature of soil organic matter affects sorption of pesticide. 1. Relationships with carbon chemistry as determined by C-13 CPMAS NMR spectroscopy. Environ Sci Technol... 

In the list of diazoketones studied by us95 mostly derivatives were included which have in solution no or only a small tendency for a Wolff rearrangement. Nevertheless we found not a single diazoketone 71 which enabled us to identify a ketocarbene 72, only the corresponding ketenes 73 could be detected. The same observation was made when we studied in collaboration with Yannoni et al." the photochemically induced deazotation of l-diazo-2-propanone in an organic matrix at 77 K, using 13C CPMAS NMR spectroscopy as the analytical tool. 

The phase transformation behavior of Py-D3C was far simpler than that reported for tetrahydrofuran/N2- and tetrahydrofuran/Xe-D3C in reference 10. We attribute this difference in part to impurities in the samples employed, samples that contained methanol and ethylenediamine according to 13 C CPMAS NMR spectroscopy. We have observed that use of Si(OCH3)4 as a silica source or ethylenediamine as a catalyst in clathrasil synthesis introduces defects that can alter phase transition temperatures by as much as 30 °C and/or introduce new phase transformations. 

The structures of 4-aryl-2,3-dihydro-lH-pyrido[l,2-c]pyrimidine-l,3-diones hydrochlorides 50 were characterized by solid-state 13C CPMAS NMR spectroscopy (08JST325). 

Kacker, T., Haupt, E. T. K., Garms, C., Francke, W., and Steinhart, H. (2002). Structural characterisation of humic acid-bound PAH residues in soil by BC CPMAS-NMR-spectroscopy evidence of covalent bonds. Chemosphere 48,117-131. 

Zeolite Y. We also substituted boron into dealuminated zeolite Y. We dealuminated zeolite Y by EDTA treatment using standard methods (4). The presence of hydroxyl nests in the product was confirmed using 29Si CPMAS NMR spectroscopy. The dealuminated material incorporated 33 times more boron than zeolite Y when treated with KOH/B2O3. These data are summarized in Table 3. The boron substituted faujasite exhibits a single sharp resonance in the NMR spectrum, consistent with structural substitution. Since the substitution level was low and would not be expected to cause large shifts in the diffraction pattern, no corrected XRD data were obtained on substituted zeolite Y. 

Surface chemistry of the alkyl/alkylidene complexes has been studied by C CPMAS NMR spectroscopy. Cp2Ta(= CH2)( CH3) is converted predominantly to a stable cation-hke Cp2Ta( CH3)2+ species on partially dehydroxylated Si02 (PDS) presumably via electrophilic addition of a proton from the PDS surface. The formation of cation-like Cp2Ta( CH3)2+ and CpTa( CH3)3+ is observed when Cp2Ta( CH3)3 and CpTa( CH3)4 are chemisorbed on PDS and dehydroxylated Si02 (DS),... 

The molecular and crystal structures of the hydrochloride and hydrobromide salts of 3(5)-methyl-5(3)-phenyl-pyrazole of 61 and 62 and the hydrobromide salt of 63 were determined by X-ray analysis and C CPMAS NMR methods <1997JMT(415)81>. A structural study of pyrazole-l-carboxamides 64 was made by X-ray crystallography and C CPMAS NMR spectroscopy <1999JMT(478)81>. 

Figure 13 Decomposition model of Baldock et al. (1992) based on CPMAS NMR spectroscopy of a Mollisol (reproduced by permission of Kluwer Academic Publishers from Biogeochemistry, 1992, 16, 1-42).

Offerdahl, T.J. Salsbury, J.S. Dong, Z. Grant, D.J.W. Schroeder, S.A. Prakash, I. Munson, E.J. Quantitation of crystalhne and amorphous forms of neotame using C CPMAS NMR spectroscopy. J. Pharm. Sci. Submitted for publication. 

Phosphorus-31 and carbon-13 CPMAS NMR spectroscopy together with ab initio calculations at the hf/6-31g levels have been used to provide information on the structure and electronic distribution of imino(triphenyl)phosphorane (12).6... 

The two isocyanate groups of BICDPM react with amino groups of the PVFA-co-PVAm chains as well as with silanol groups of the silica surface. Structure analysis of PVFA-co-PVAm/silica particles cross-linked with BICDPM was carried out by means of solid state 13C CPMAS NMR spectroscopy (Fig. 6) and XPS (Fig. 2b). 

It is demonstrated that the presence of a single helical conformation, as revealed by C NMR spectroscopy, plays a dominant role for the unique properties of higher molecular-weight linear and branched (1+3)-6-D-glucans. We are planning to analyze the conformation and dynamics of cross-linked region by means of CPMAS NMR spectroscopy. 

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