Carbon-13 NMR analysis

Use of Carbon-13 NMR Analysis in the Characterization of Alternating Copolymers Prepared by Chemical Modifications of 1,4-Polvdienes... 

Robert DR, Gellerstedt G, Bardet M (1986) Carbon-13 NMR analysis of lignins obtained after sulfonation of steam exploded aspen wood Nord Pulp Pap Res J 1 18-25... 

Other stabilised ylides that have been structurally characterised recently include (8), which also adopts a syn enolate conformation, and (9a). Carbon-13 NMR analysis of (9a) and (9b) show extensive delocalisation of the negative charge." ... 

Yields for the polar fraction pyrolyses are depicted in Figure 5. The combined n-alkane/1-alkene yields for carbon numbers less than 15 were reasonably good for a 15-minute pyrolysis but secondary fragmentation sharply reduced the yields for longer stress periods. The olefins were more reactive in the polar environment than the saturate environment and were generally minor products at all stress times. The low yield of alkanes and alkenes for carbon numbers above 14 corroborates the average chain length of 13 found by carbon-13 nmr analysis. 

J Schaefer, EO Stejskal, R Buchdahl. Magic-angle carbon-13 NMR analysis of motion in solid glassy polymers. Macromolecules 1982 384-405, 1977. 

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. 

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

Carbon-13 NMR was used as the reference method to enable comparison of FT-Raman and FTIR spectroscopies as isotacticity determination methods. Calibration curves relating Raman scattering and IR absorption ratios to the carbon-13 NMR results are presented. The repeatability for both FT-Raman and FTIR measurements was comparable to that of carbon-13 NMR analysis and there was good correlation between between carbon-13 NMR and FT-Raman/FTIR results. The reliabilities of the three methods are statistically evaluated and compared. 9 refs. 

Yamamoto H, Horii F (1993) CPMAS carbon-13 NMR analysis of the crystal transformation induced for Valonia cellulose by annealing at high temperatures. Macromolecules 26 1313-1317... 

Wu RL, Wang XL, Wang YZ, Bian XC, Li F (2009) Cellulose/soy protein isolate blend films prepared via room-temperature ionic liquid. Ind Eng Chem Res 48(15) 7132-7136 Yamamoto H, Horii F (1993) CPMAS carbon-13 NMR analysis of the crystal transformation induced for Valonia cellulose by annealing at high temperatures. Macromolecules 26 (6) 1313-1317... 

Carbon-13 NMR Analysis of Polyepichlorohydrin. Natural-abundance carbon-13 NMR spectra at 22.6 MHz were measured in benzene at 70°C. with proton noise decoupling, using a Bruker HFX-10 spectrometer equipped with a Nicolet 1085 Fourier transform spectroscopy accessory. 

Previous authors have taught the principles of solving organic structures from spectra by using a combination of methods NMR, infrared spectroscopy (IR), ultraviolet spectroscopy (UV) and mass spectrometry (MS). However, the information available from UV and MS is limited in its predictive capability, and IR is useful mainly for determining the presence of functional groups, many of which are also visible in carbon-13 NMR spectra. Additional information such as elemental analysis values or molecular weights is also often presented. 

Instrumentation. The NMR Process. Chemical Shift. Spin-spin Coupling. Carbon-13 NMR. Pulsed Fourier transform NMR (FT-NMR). Qualitative Analysis - The Identification of Structural Features. Quantitative Analysis. Applications of NMR Spectrometry. 

The synthesis of hydroxy-3-aminoethane thiosulfuric acid (AETSAPPE) is shown in Scheme II. The same basic conditions used for the polymer synthesis were employed to synthesize the model compound (AETSAPPE) although the work-up conditions were less stringent. The structure was confirmed by carbon-13 NMR and elemental analysis. 

The carbon-skeleton has been viewed directly with the help of Carbon-13 NMR spectroscopy on a particle basis since early 1970 s whereas -NMR spectrometry started in late 1950 s. The valuable contribution made by various researchers, between 1976 and 1980, has virtually placed 13C-NMR to a strategically much advanced stage where it gives a clear edge over 1H-NMR in terms of not only its versatility but also its wide application in analysis. 

The polysaccharide consisted entirely of fructose methylatlon analysis showed that the primary fructose linkages were P(2- 6) fructofuranosyl linkages. Carbon 13 nmr showed the product to be a levan type fructan. 

D.J. Vforsfold, NRC, Ont. Problems often arise in carbon-13 NMR work with the integration of the peaks. In the analysis of copolymer systems it would be useful to have very good peak integration. Can you in fact succeed in this ... 

Nuclear magnetic resonance spectroscopy of dilute polymer solutions is utilized routinely for analysis of tacticlty, of copolymer sequence distribution, and of polymerization mechanisms. The dynamics of polymer motion in dilute solution has been investigated also by protoni - and by carbon-13 NMR spectroscopy. To a lesser extent the solvent dynamics in the presence of polymer has been studied.Little systematic work has been carried out on the dynamics of both solvent and polymer in the same systan. 

Formdbek V, Kubeczka KH, Essential Oils Analysis by Capillary Gas Chromatography and Carbon-13 NMR Spectroscopy, John Wiley Sons, Chichester, Great Britain, 1982. 

K. Formazek, K. H. Kubeczka, Essential Oil Analysis by Capillary Chromatography and Carbon-13 NMR Spectroscopy, J. Wiley Sons, New York 1982. 

The potential of carbon-13 NMR in the analysis of keto-enol tautomerism has been demonstrated for 2,4-pentanedione (acetylacetone) and dimedone [293]. Quantitative evaluation of equilibrium concentrations is possible by application of the inverse gated decoupling technique illustrated in Fig. 2.23. 

Fig. 4.13. illustrates how to apply carbon-13 NMR for analysis of tautomerism in heterocyclic chemistry 3-Methyl-5-oxo-l-phenyl-4,5-dihydropyrazole (the Knorr-pyrazolone ) is shown to exist as the CH tautomer B with a CH2 carbon at 43.1 ppm in chloroform solution (Fig. 4.13(a)), while the OH tautomer A predominates (90%) in hexadeuteriodimethyl sulfoxide (Fig. 4.13(b) [73 i]. 

Fig. 4.17 illustrates the potential of carbon-13 NMR to detect the presence of isotactic (a), syndiotactic (b), and atatactic (c) vinyl polymers with polypropylene as sample [521], The spectrum of atactic polypropylene (Fig. 4.17(c)) displays the signals of all possible stereosequences including iso- and syndiotactic ones. Using the empirical increment systems for alkane carbon shift prediction [85, 201, 202] and including y effects of Zy = — 5 ppm specifically obtained by analysis of stereoisomeric polypropylene partial sequences between 3,5-dimethylheptane and 3,5,7,9,11,13,15-heptamethylheptadecane as a heptad model, the methyl carbon-13 shifts of all 36 possible heptads can be calculated... 

The development of carbon-13 NMR during the last eight years has been characterized by a continual increase in the sensitivity and quality of spectra. A reduction in measuring time - equivalent to an enhancement in sensitivity has been achieved mainly by cryomagnet technology. The efficiency with which NMR information can be obtained has been substantially improved by new computer-controllable pulse sequences for one-and two-dimensional NMR experiments. A selection of these new methods, in particular, those used for multiplicity analysis and homo- or heteronuclear shift correlations, is presented in chapter 2 of this edition. 

Pihlaja, K. and Kleinpeter, E., Carbon-13 NMR Chemical Shifts in Structural and Stereochemical Analysis, VCH, New York, 1994. 

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