Proton resonance spectroscopy

Figure 3-10. Proton resonance spectroscopy of poly(methyl methacrylates) in 0.1 g/ml chlorobenzene solution at 135°C and 220 MHz. Left the )8-methylene signals given by tetrads. Right the a-methylene proton signals given by pentads. Above predominantly syndiotactic PMMA. Below predominantly isotactic PMMA.

With the employment of an appropriate model system, proton resonance spectroscopy has proved applicable also for following the transformation of a contact ion pair into a solvent-separated ion pair. Naseer Ahmad and Day [Na 77] used the system sodium tetraethylaluminate-benzene-donor solvent for this purpose. The spin-spin interaction between the and the Al in the tetraethylaluminate served as the source of information this is reflected by the resonance spectrum of the methylene protons. [Pg.129]

New possibilities for such purity examinations have opened up with the development of C-resonance spectroscopy. By means of this method it is now possible to distinguish between carbon atoms in different chemical environments. In accordance with the above considerations, this may be utilized for qualitative investigations. It should be noted, however, that the sensitivity of the carbon-resonance method is lower than that of proton-resonance spectroscopy. Owing to the low abundance of the isotope, the measurements must be carried out in more concentrated solutions. At the same time, the resolution of carbon-resonance spectroscopy is higher than that of proton-resonance spectroscopy, hence the former can be used for the detection of impurities (when present in sufficiently high... [Pg.255]

Symons MCR, Benbow JA, Pelmore H (1984) Interactions between calcium ions and a range of monosaccharides studied by hydroxy-proton resonance spectroscopy. J Chem Soc Faraday Trans 80 1999 2016. doi 10.1039/F19848001999... [Pg.293]

Investigations of the polymerization kinetics of aniline and its relatives (as opposed to the oxidation kinetics observed in the initial electrooxidation step) are few. Most studies reported so far are devoted to morphological aspects, nucleation [285-288], nucleation dimensionality, and related features. Preferably, electrochemical (i.e., traditional) methods of investigation were employed. The first application of proton resonance spectroscopy to the investigation of polymerization kinetics of PANI has been reported [289]. Only chemical oxidation (precipitation and dispersion polymerization) was employed the spectroscopy was used just to monitor the concentration of the monomer in the solution phase. Various oxidizing compounds of different effectiveness were studied. An investigation of the chemical oxidation with... [Pg.225]

Proton resonance spectroscopy has been used to study the tautomerism of 4-hydroxypyridine and its 1-oxide, with results in agreement with those obtained by other physical methods discussed here. Resonance spectroscopy also indicated that the cations of 4-hydroxypyridine, 1-methyl-4-pyridone and 4-methoxypyridine are of the type (32), that of 4-hydroxy-pyridine 1-oxide as (33), and that 2-pyridone cation is protonated on... [Pg.145]

Proton resonance spectroscopy has been used to determine the sites of protonation of thiopyridines and aminopyridinesi234, ... [Pg.279]

Braunschweiler L and Ernst R R 1983 Coherence transfer by isotropic mixing application to proton correlation spectroscopy J. Magn. Reson. 53 521 -8... [Pg.1464]

Instmmental methods of analysis provide information about the specific composition and purity of the amines. QuaUtative information about the identity of the product (functional groups present) and quantitative analysis (amount of various components such as nitrile, amide, acid, and deterruination of unsaturation) can be obtained by infrared analysis. Gas chromatography (gc), with a Hquid phase of either Apiezon grease or Carbowax, and high performance Hquid chromatography (hplc), using siHca columns and solvent systems such as isooctane, methyl tert-huty ether, tetrahydrofuran, and methanol, are used for quantitative analysis of fatty amine mixtures. Nuclear magnetic resonance spectroscopy (nmr), both proton ( H) and carbon-13 ( C), which can be used for quaHtative and quantitative analysis, is an important method used to analyze fatty amines (8,81). [Pg.223]

Nuclear Magnetic Resonance Spectroscopy. Nmr is a most valuable technique for stmeture determination in thiophene chemistry, especially because spectral interpretation is much easier in the thiophene series compared to benzene derivatives. Chemical shifts in proton nmr are well documented for thiophene (CDCl ), 6 = 7.12, 7.34, 7.34, and 7.12 ppm. Coupling constants occur in well-defined ranges J2-3 = 4.9-5.8 ... [Pg.19]

P. Diehl in T. Axenrod and G. Webb, eds. Nuclear Resonance Spectroscopy of Nuclei Other Than Protons, John Wiley Sons, Inc., New York, 1974, pp. 275-285. [Pg.16]

Bovey, F A, Jelmski, L, Mirau, P A Nuclear Magnetic Resonance Spectroscopy, 2nd ed, Acadermc Press New York, 1988 Proton and Fluorine Nuclear Magnetic Resonance Spectral Data, Vanan Instruments/Japan Halon Tokyo, 1988... [Pg.1079]

Up to the present the principal interest in heteroaromatic tautomeric systems has been the determination of the position of equilibrium, although methods for studying fast proton-transfer reactions (e.g., fluorescence spectroscopy and proton resonance ) are now becoming available, and more interest is being shown in reactions of this type (see, e.g., references 21 and 22 and the references therein). Thus, the reactions of the imidazolium cation and imidazole with hydroxyl and hydrogen ions, respectively, have recently been demonstrated to be diffusion controlled. ... [Pg.318]

An X-ray crystallographic study of 2-hydroxy-4,6-dimethylpyrimi-dine led to no conclusions regarding its structure. Because of the rapid exchange of the NH protons of pyrimidin-2-one both in dimethyl sulfoxide and in water, nuclear magnetic resonance spectroscopy does not afford positive evidence for either the oxo or the hydroxy formulation. The statement that 4,6-dimethylpyrimidin-2-one had been isolated in two modifications, 94 and 95, was soon disproved. ... [Pg.370]

It is interesting to note that the acyclic analog, nitroguanidine, exists in the symmetrical form 288 rather than as 289. Structure 288 has been established by ultraviolet and proton nuclear magnetic resonance spectroscopy. X-ray crystallography, dipole moments, and ipK measurements (see reference 367 and references therein). [Pg.425]

In favorable cases, cyclization reactions may be useful in estab-hshing configurations, but these methods may also be complicated by isomerizations. It is clear that other approaches are necessary to resolve this structural question. This has been accomplished recently for the isomers of a related system (55) using proton magnetic resonance spectroscopy. [Pg.97]

The rate of formation of the pseudooxazolone may be followed conveniently by proton magnetic resonance spectroscopy. ... [Pg.103]

Studies of Deoxy Sugars by Proton Magnetic Resonance Spectroscopy... [Pg.236]

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