C-NMR analysis

More recently, we[7] observed that thermal sequence randomization of an ordered sequence copolyester occurred rather rapidly at an elevated temperature through ester exchange reactions. The process could be followed quantitatively using C-13 NMR analysis. 

The formaldehyde content of each sample was determined by use of the hydroxylamine hydrochloride method. The addition of 5% by wt of urea was also used to capture the free formaldehyde as te(hydroxymethyl) ureas in order to simplify the C-13 NMR analysis. Samples were kept at -4°C until analyzed. 

Saigne-Soulard, C. et al. (2006) C-13 NMR analysis of polyphenol biosynthesis in grape cells Impact of various inducing factors. Anal. Chim. Acta 563, 137-144... 

Reqiospecificty. Figure 7 shows a C-13 NMR analysis of the chain ends for a low molecular weight sample produced in pentane at 80 C. The vlnylidene and n-propyl chain ends are consistent with fi-hydride termination and hydride initiations with 1,2-regiospecificty. The isobutyl groups reflect transfer to Al and initiation reactions with methyl groups. 

Various destructive and non-destructive methods of analysis have been tested and H-l and C-13 NMR have, among other techniques provided valuable structural information on soluble humic acids and fulvic acids 48, Humin, on the other hand has withstood detailed non-destructive analysis. 

Watts, D. C. (1979). C-13 NMR spectroscopic analysis of polyelectrolyte cement liquids. Journal of Biomedical Materials Research, 13, 423-35. 

H2 + CH4, D2, P2 + Tetralin, GO + H2O were selected and reduction was conducted by varying the reaction time. Each isolated fraction was subjected to ultimate analysis, H-NMR, C-13 NMR, molecular weight measurement and the structural parameters were calculated. The results of the study of these structural parameters in the course of the reactions were evaluated and the reaction mechanisms thereof are discussed below. 

As can be seen from Fig 2b, the solid state C-13 nmr spectrum of T. aestivum also shows sets of enhanced resonances at 61 ppm and 169.6-174.9 ppm respectively (24). However, their relative intensities are very different from that observed for L. leucocephala. Indeed, it can immediately be seen that very little reduction of the administered precursor to hydroxymethyl analogues (at 61 ppm) has occurred. On the other hand, the dominant resonances at 169.6 and 174.9 ppm are coincident with bound hydroxycin-namic acids (e.g. ferulic 5a) and its esters (31). Subsequent analysis of its isolated acetal lignin derivative (32) indicated that much of the lignin contained hydroxycinnamate residues (33). 

J. K. Whitcscll, M. A. Minton, Stereochemical Analysis of Alicyclic Compounds by C-13 NMR Spectroscopy, Chapman Hall, London 1987. 

Carbon-13 nmr Analysis. Samples of the various fractions were submitted to analysis by C-13 nmr. The C-1,3 spectrum affords a distinct separation of the aromatic and aliphatic absorption regions plus a good resolution of many peaks due to specific molecular structure. Thus, a good amount of useful information can be obtained even for a complex mixture such as a fuel fraction. With respect to the present study, the aliphatic region of the spectrum is of particular importance. 

J. Schaefer, "The Carbon-13 NMR analysis of synthetic high polymers," in Topics in Carbon-13NMR Spectroscopy, edited by G. C. Levy (Wiley-Interscience, New York, 1974), vol. 1. 

Inclusion complexation of prednisolone with three Cyclodextrins, a (3 and 7-homologues, in aqueous solution and in solid phase was examined using UV absorption, CD, C 13 NMR, C 13-CP/MAS-NMR, X-ray diffractometry and thermal analysis. The spectroscopic data suggested the different inclusion mode of prednisolone within the three cyclodextrin cavities. X-ray diffraction patterns of the complexes differed significantly from those of the physical mixtures (14). 

On the other hand, we already described the study of C-13 NMR and X-ray photoelectron spectral analysis for chitosan to clarify the electronic structure in the formation of properties of biological molecule from the DFT calculations [3] and to understand the changes in adsorption behavior of chemically modified biopolymer chitosan (crosslinked biopolymer) [4],... 

We already studied the electronic state of chitosan from C-13 NMR and X-ray photoelectron spectral analysis from the DFT calculations [3]. In this study, we focus on analysis of Raman and valence X-ray photoelectron spectra for carbonized chitosan him with Kr+ ion irradiation to clarify the constitutional structure for the depth profile assignments in nm and p,m ranges, respectively. 

A new organotin monomer tributyltin -chloroacrylate (TCA) was synthesized in our laboratory. Detailed studies on homopolymerization and copolymerization were undertaken. Copolymerization was carried out with styrene (ST), methyl methacrylate (MMA) and acrylonitrile (AN). Both homopolymer and copolymers were characterized by IR, IF and C-13 NMR and tin analysis. Reactivity ratios were determined using Kelen-Tudos method. Reactivity ratios were r =0.500 and r = 0.170 for TCA-ST, r = 1.089 and r = 0.261 for TCA-MMA and r =1.880 and r = 0.243 for TCA-AN respectively. Micro-structures of homopolymer and copolymers were studied using C-13 NMR spectroscopy. Data obtained were compared with those of tributyltin methacrylate (TBTMA) and its corresponding copolymers. The results indicate that TCA is more reactive than TBTMA. 

Zupke, C. and Stephanopoulos, G. (1995) Intracellular flux analysis in hybridomas using mass balances and in-vitro C-13 nmr. Biotechnol Bioeng, 45, 292-303. 

Bhattacharyya, j., and S. C. Pakrashi Carbon-13 NMR Analysis of Some 4-Quinazolinone Alkaloids and Related Compounds. Heterocycles 14, 1469 (1980). 

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