Cross-polarization magic angle spinning CP/MAS NMR

Table 1. Structural carbon distribution (%) of the humic acids extracted from soil horizons, adopted from Xing (2001). The distribution was calculated from solid state 13C Cross-Polarization Magic-Angle-Spinning (CP/MAS) NMR spectra. Chemical shift assignment for carbon functional groups alkyl 0-50 ppm O-alkyl 50-117 ppm aromatic 107-165 ppm.

The X-ray and solution structures of lithium fluorenide (68) have been reported earlier125,126. It was found that whereas the X-ray study suggested that the lithium is asymmetrically positioned above the fluorenyl unit, calculations and solution 13C NMR showed a symmetrical structure. Thus, Johnels and Edlund used 13C cross-polarization/magic angle spinning (CP/MAS) NMR in order to get further insight about the structure 68. 

The solid-phase 13C cross-polarization/magic angle spinning (CP/MAS) NMR, as a tool for conformation prediction, revealed that the solid-phase conformation of the nine-membered ring crown cavity in naphtho-9-crown-3 is different from benzo-9-crown-3. The two key C-0-CH2 units are predicted to be out of naphthalene plane, and the two C-C-O-CH2 torsion angle values are close to each other <2000JST(526)185>. 

A 13C nuclear magnetic resonance (NMR) study in solution and in the solid state has been reported for three thermochromic spirooxazines, 29-31.32 From a quantitative analysis of I3C cross-polarization/magic-angle-spinning (CP-MAS) NMR spectra shielding anisotropies were estimated and a correlation of these characteristics with thermochromic activity was suggested. 

It has been demonstrated that cross-polarization/magic-angle spinning (CP/MAS) NMR spectroscopy is the most powerful means available to characterize the structure and dynamics of inorganic polymers in the solid state [1], The most recent development of a variable-temperature (VT) spinner provided an indispensable means to study slow chemical exchange, molecular motion and phase transitions of inorganic polymers. 

A strong signal at 10 ppm in the solid state cross polarization/magic angle spinning (CP/MAS) NMR spectrum of stone-ground wood pulp (SOW) treated with trimethyl phosphite, has been attributed to a cyclic phosphite ester formed via hydrolysis of an oxyphosphorane adduct of trimethyl phosphite and ort/to-quinones present in lignin, as shown in Scheme 6.2 [64-66]. 

The temperature-dependent NMR spectra of the PLA samples collected under the varying temperature from 20 to 80 °C are shown in Fig. 6. Cross polarization-magic angle spinning (CP-MAS) NMR experiments were carried out on a Varian 400 NMR system spectrometer operated at 100.56 MHz for resonance with a cross polarization contact time of 2 ms (Fawcett, 1996). A zirconium oxide rotor of 4 mm diameter was used to acquire the NMR spectra at a spinning rate of 15 kHz. Each sample was packed into a 4 mm cyUnder-type MAS rotor. A set of temperature-dependent NMR spectra were obtained under varying ambient temperature from 20 to 80 °C at every 20 °C step. The heating rate was approximately 10 °C per an hour. 

The primary components and the chemical structure of the raw peat and the solid product were further analyzed by Fourier transform infrared spectroscopy (FTIR) 0ASCO 670 Plus) using the Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) technique and the JASCO IR Mentor Pro 6.5 software for spectral analysis. The cross polarization/magic angle spinning (CP/MAS) NMR spectrum of raw peat and the solid... 

Saito, H., R.Tabeta, and S. Hirano. 1982. Ahighresolution C NMR study of chitin, chitosan andiV-acylchitosans by cross polarization/magic angle spinning (CP/MAS) NMR spectroscopy. In Proceedings of the Second International Conference on Chitin and Chitosan, eds. S. Hirano and S. Tokura, pp. 77-81. Tottori, Japan The Japanese Society of Chitin and Chitosan. 

Very well defined calixarenes bonded on silica gel were later prepared firom distal 1,3-chloroacetate derivatives of icri-butyl calix[4]arene and Y-(ethylenediamino)-propyl-triethoxyl-silane. Si cross-polarization magic angle spinning (CP-MAS) NMR spectroscopy furnished evidence on the postulated crosshnking of a large portion of the trifunctional alkylsilyl groups to the surface of the silica gel. Retention times increased when sodium counterions were added to... 

Solid state cross polarization magic angle spinning (CP-MAS) NMR has recently allowed the conformation of lamellar crystals to be characterized. Comparison of the solution and solid state CNMR chemical shifts of cyclic alkanes with 16-80 carbon atoms indicated that the solid state conformation is retained in solution for cyclic alkanes with up to 32 carbon atoms,with fast conformational interconversions of the ring occurring in the solid state as well as in solution. In the larger cyclic alkanes, however, molecular motion is frozen in the solid state, but resumes in solution, as is the case with n-alkanes (nine to 36 carbon atoms) and PE. ... 

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