C CPMAS-NMR

Some reviews relevant for this section concern N CPMAS [86AG(E)383] of pyrazoles, including CPMAS results (93MRC107) and proton transfer in solid heterocycles (94JHC695). The most relevant studies reported in Table X are (1) the use of C CPMAS NMR to identify... 

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. 

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>. 

The C CPMAS NMR spectrum of a 5% (wt/wt) loading of bupivacaine in lipospheres and the protein matrix is shown in Fig. 9A, with the spectra of the protein matrix, lipospheres, and bupivacaine-fb shown... 

Fig. 8 C CPMAS NMR spectra of (A) tristearin (B) bupi-vacaine-fb (20% wt/wt) in tristearin (80% wt/wt) (C) bupi-vacaine-fb (10% wt/wt) in tristearin (90% wt/wt) (D) bupivacaine-HCl (20% wt/wt) in tristearin (80% wt/wt) (E) bupivacaine-HCl (10% wt/wt) in tristearin (90% wt/wt). The vertical scale has been expanded to facilitate the identification of the bupivacaine form present. Asterisks ( ) denote spinning sidebands incompletely suppressed by the TOSS sequence. (From Ref. l)...

Fig. 9 C CPMAS NMR spectra of (A) 5% (wt/wt) bupi-vacaine loaded into lipospheres and protein matrix (B) protein matrix (C) lipospheres and (D) bupivacaine-fb. Asterisks ( ) denote spinning sidebands incompletely suppressed by the TOSS sequence. (From Ref 1)...

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. 

In NMR, extensive studies have shown that solid-state CPMAS NMR spectra of most soils can be analyzed quantitatively(5,25,26) if one considers the relaxation and cross polarization lanetics of the compounds observed in the spectra. We can extend these results to imply that solid-state N CPMAS NMR spectra are also quantitative. Comparable to C CPMAS NMR, in a N CPMAS NMR experiment, quantification problems may arise from 1) incomplete relaxation of the spins during the experiment, 2) incomplete polarization transfer because of the isolation of protons from nitrogen atoms and 3) spinning side bands. The effects of these parameters on a C CPMAS NMR spectrum are extensively discussed by Wilson.(5)... 

Some of the earliest chemometric NMR analysis of materials involved the PCA of organic peat using C CPMAS NMR spectra,and the analysis of H and C NMR relaxation parameters in coal. Chemometrics and C CPMAS has also been applied to classify soil organic matter. Clayden and co-workers have used FA of the time domain F NMR signal in poly(tetrafluoroethane), PTFE polymers as a method to measure crystallinity. It was demonstrated that the dominant principal component did not correlate well, but that the scores of second and third principal component show an excellent correlation with the PTFE crystallinity. PLS methods have also been used to determine... 

Preston, C. M., Dudley, R. L., Fyfe, C. A., and Mathur, S. P. (1984). Effects of variations in contact times and copper contents in a C CPMAS NMR study of samples of four organic soils. Geoderma 33, 245-253. 

The stereolabile helical enantiomers of dimesityl sulfoxide and sulfone have been characterized by C CPMAS NMR, which show that the helical enantiomers are stable in the crystalline state. 

The 3-alkyl, benzyl and phenyl derivatives of l-(2-hydroxy-4-bromophenyl)-3-methyl-4-imidazolin-2-one have been studied by solid-state C CPMAS NMR. The differences in chemical shifts A = 5(liquid) — 8(solid) are significant for aromatic carbons C3 ( — 2.9 ppm), C4 (3.6 ppm) and C5 (—3.9 ppm) and C7 (—1.5 ppm), which are adjacent to N1-C4, and are subject to the largest changes of the environment during reorientation of the imidazolin-2-one moiety. 

The 5-carboxymethyl-1,2,4-triazole and 5-oxo-l,2,4-triazine derivatives have been examined by C CPMAS NMR. ... 

Crystalline a-D-galacturonic acid monohydrate has been studied by C CPMAS NMR and X-ray crystallography. The molecular dynamics have been investigated by evaluating C spin-lattice relaxation in the rotating frame (Tip) and CSA properties of each carbon. It has been found that only limited molecular motions can be detected in the low frequency (<10 Hz) range by Tip( C) measurements and changes of CSA properties as a function of temperature. 

A gallium citrate complex (NFl4)3[Ga(C6H507)2]-4H20 has been studied by C CPMAS NMR. The number and intensities of the resolved resonances in the spectrum are found to be consistent with the X-ray structure. 

CHN analysis and C CPMAS NMR examinations. The total amount of CO2 produced in the presence of catalyst is in good agreement with the values obtained in the uncatalyzed liquid-... 

The C CPMAS NMR spectra of antipyrine, l-phenyl-3-hydroxypyrazole and l-p-bromophenyl-... 

The structure of indazolinone and some of its derivatives was determined by the combined used of crystallography, C CPMAS NMR, and N NMR <86JCS(P2)1677>. It was concluded that indazolinone exists as such (67a) in the solid state but only as a minor isomer (15%) in DMSO solution, where the 3-hydroxy-l//-indazole tautomer (67b) predominates (85%). The 3-hydroxy-2//-indazole tautomer (67c) has never been observed. The equilibrium between 2-hydroxy-3-methyl-indazole and 1/f-3-methylindazole-2-oxide has been studied in DMSO, methanol, and trifluoro-methanol by C and N NMR spectroscopy <87MRC721>. The position of the equilibrium was found to be dependent on the acidity of the solvent, the hydroxy form being predominant in weakly acidic media. 

Cobalt(II) and nickel(II) complexes of bipyrazoles, like (79), and bispyrazoles, like (80), are either dimeric or polymeric <84ICA99>. The x-ray structure and C CPMAS NMR spectra of (79) and (80) were reported <94SA(A)727>. Ligands similar to (80) have also been used to prepare rhodium(I) complexes <84JOM(276)79>. 

Yang et al. [53] prepared a novel series of metal-containing poly(imide)s. Polymers of pyromellitic dianhydride with the zinc, strontium, lead, calcium and nickel salts of p-aniline sulfonic acid, were prepared and examined by C CPMAS NMR. There was little difference in the chemical shifts of the dianhydride carbons, compared with the chemical shifts of the poly(imide) with diaminodiphenyl methane. 

NMR spectroscopy and in particular solid-state NMR spectroscopy proved to be a powerful method for studying the mechanism and extent of reaction in complex poly(imide) materials. In particular, during the cure of BMI resins, careful use of C CPMAS NMR indicated that measurements of the extent of cure by DSC were significantly overestimated [86, 87]. This article demonstrates that NMR spectroscopy has been able to characterize the structure of condensation poly(imide)s and, more successfully, the cure of BMI, PMR and acetylene-terminated resins. 

Figure 2 C-CPMAS NMR spectra of M sexta larval, pupal and adult cuticles The larval and adult samples are devoid of cuticle from the head and appendages Scales were removed from adult cuticle (from Kramer et al. 43).

Nowadays, i C-CPMAS NMR spectra are routinely recorded and most of spin 1/2 nuclei are accessible. Although not yet a routine practice H and as well as two-dimensional spectra can be also recorded. 

Figure 4 Experimental (upper traces) and simulated C CPMAS NMR spectra of the carbonyl carbon of 2-chloro-2-(phenylsulfonyl)-l-phenylpropanone, showing evidence for residual dipolar coupling between and From Ref. 61. Reproduced by permission of the American...

Characterization of pyrolyzed tobacco and tobacco components by C CPMAS NMR and FTIR 54th Tobacco... 

Figure 11 C CPMAS NMR spectra of n-butylamine (a) adsorbed to the surface of...

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