Sulphoxides resonance spectroscopy

Edwards two-parameter equation 549 Electrochemical oxidation of sulphides 76, 252, 253 of sulphoxides 968, 987, 1043 Electrochemical reduction of sulphones 962, 963, 1002-1041 of sulphoxides 933, 1041, 1042 Electronegativity, of the sulphur atom 584 Electronic effects 390, 484-535 Electron scavengers 892, 896 Electron spin resonance spectroscopy 874, 890-895, 1050-1055, 1082, 1083, 1090-1093... 

Markham, K.R. Geiger, H. 1993. H nuclear magnetic resonance spectroscopy of flavonoids and their glycosides in hexadeuterated dimethyl sulphoxide. In The... 

Tropothione 2 can be oxidized with an equimolar amount of m-chloroper-benzoic acid. Below 213 K, a sulphinic species, tropothione-S-oxide 3, has been isolated.42 In turn, S-oxide 3 with CF3COOH forms a sulphenic acid 4, which is quite stable at room temperature. Compounds 3 and 4 have been characterized with the aid of 33S NMR spectroscopy. The 33S chemical shift is -6 ppm for 3 and —85 ppm for 4. In agreement with findings for sulphides and sulphoxides, the bonding of an oxygen atom to sulphur in tropothione induces a downfield shift of the 33S resonance. 

Abbreviations KMB, 2-keto-methylthiobutyric acid DMPO, the spintrap, 5,5-dimethyl- 1 -pyroline-A -oxide ESR, electron-spin resonance (=electron paramagnetic resonance, EPR) spectroscopy DMSO, dimethyl sulphoxide Phe, phenylalanine Tyr, tyrosine HPLC, high-performance liquid chromatography. 

Perhaps the best method for the determination of the solvation numbers of cations in their non-aqueous solutions is nuclear magnetic resonance (NMR) spectroscopy [Sw 62], The procedure is based on the fact that under optimal conditions the NMR absorption band of the coordinated solvent molecules separates from that of the free solvent, and the ratio of the magnitudes of the areas under the two bands provides direct information on the solvation number of the cation. The conditions for the separation of the two NMR signals are that the rate of exchange between the coordinated solvent and the free solvent molecules should be comparatively low, and the spin relaxation time should be short. Successful studies in dimethyl sulphoxide [Th 66], ditnethylformamide [Fr 67a, Fr 67b, Ma 67] and methanol [A1 69b] have been reported. Jackson et al. [Ja 60] have developed a method that can also be used in cases where the proton resonance signals of the coordinated solvent molecules and the free solvent are so close to one another that they do not separate [Ch 68, Al 69a]. 

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