Nuclear magnetic resonance phenols

Servili M, Baldioli M, Selvaggini R, Macchioni A and Montedoro GF. 1999. Phenolic compounds of olive fruit one and two-dimensional nuclear magnetic resonance characterization of niizhenide and its distribution in the constitutive parts of fruit. J Agric Food Chem 47(1) 12—18. 

Tables 3-2 and 3-3 summarize the infrared and proton-NMR (nuclear magnetic resonance) spectroscopic properties of alcohols and ethers. In the proton NMR, the oxygen atom is deshielding. Phenols and alcohols rapidly exchange protons so their NMR spectra are solvent dependant. The alcohol and ether groups don t have any characteristics absorptions in UV-vis spectra.

The reaction of few phenols with acetylenic esters is reported in the literature. " George and co-workers, on the basis of detailed nuclear magnetic resonance (NMR) studies of the product mixtures formed in the reaction of several phenols with DMAD, have concluded that, as the size of the attacking nucleophile increases, there is a greater tendency for the formation of maleates, which are sterically more favored as compared to the fumarates. 

The determination of polyphenolics may result in interference due to co-elution of phenolic acids and procyanidins. This problem can be eliminated by fractionation of polyphenolics into acidic and neutral polyphenolics prior to sample injection into the HPLC system. Because the fractionation techniques effectively improve the resolution of many polyphenolic peaks in the reversed-phase HPLC system, it is suggested that further characterization and identification of unknown peaks be conducted by additional methods such as mass spectrometry and nuclear magnetic resonance. 

Other modes of detection, such as nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR), could be advantageous detection techniques, especially to validate the HPLC of phenolics in various foods, but the cost and complexity of the instrumentation limit the... 

Analysis of the degradation products obtained from pyrolysis and oxidative degradation studies suggests that terrestrial humic substances are highly aromatic (c.70% of total C). However, these techniques tend to overemphasize the importance of aromatic and phenolic units. Non-degradative techniques, such as 1H and 13C nuclear magnetic resonance, probably give more realistic aromatic carbon contents of 20—50% for soil humics,... 

The determination of the profile of the phenolic fraction was performed for the first time by Bianco et al. [7] by nuclear magnetic resonance of proton, on different olive cultivar samples, appropriately selected. Obviously, the proposed NMR determination of the phenolic profile is not an alternative to HPLC procedures, but constitutes a rapid, alternative methodology to examine the phenolic contents in relation to the main components. In fact, the sensibility of NMR technique does not evidence components that are present in quantities less than 5% of the total. 

At VirginiaTech, 3,3 -disulfonate, 4,4 -dichlorodiphenylsulfone co-monomers with varying degrees of sulfonation were prepared from commercially available monomers. Nuclear magnetic resonance (NMR) spectroscopy was conducted on selected polymeric films to investigate the level of sulfonation. The NMR results showed that the sulfonation levels could be quantified very accurately. The water uptake of bi-phenol sulfone (BPSH) films increased with an increase in the degree of sulfonation. The membrane samples drawn from BPSH40 with 20, 30 and 40 K molecular... 

The suprafacial process in Scheme 6 is therefore indicated and the conformations shown in 3a and 4d would fit the results. The syn nature of the nitrogen and the phenolic OH can be inferred from nuclear magnetic resonance (NMR) (48,49) and infrared spectroscopic (50) studies. These are in accord with electronic absorption spectra of constrained analogues and bound and unbound imines (51). 

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