Nuclear magnetic resonance spectra, solvent effects

Nuclear magnetic resonance studies on meso-ionic l,2,4-triazol-3-ones (200) were used to examine their relationship to the alternative l,3,4-oxadiazol-2-imine structure (153). The effect of solvent polarity upon the ultraviolet spectrum of anhydro-3-hydroxy-1,4-diphenyl-1,2,4-triazolium hydroxide (200, R = = Ph, R = H) has been discussed... 

With the exception of l,6-naphthyridin-8-ols, nuclear hdyroxy-1,6-naphthyridines would be expected to exist as the corresponding naphthyridinones. This has been confirmed by infrared,1035 ultraviolet,1026 and nuclear magnetic resonance spectral means.639 Other physicochemical studies of these oxy-1,6-naphthyridines include IR stretching frequencies1019 and ionization constants1040 of 1,6-naphthyr-idin-8-ols the mass spectra of 1,6-naphthyridinones the effect of solvents on the UV spectrum of an 8-hydroxy-1,6-naphthyridine derivative 773 and X-ray analysis of the dilactam, 4-hexyl-3,4,4a,5-tetrahydro-l,6-naphthyridine-2,7(l//,6Z/)-dione (1), in connection with its crystallization as self-assembled hydrogen-bonded polymers.549... 

If the objective is identification (qualitative analysis), it suffices to compare the spectrum of the analyte with that of a standard, both recorded in the same solvent and at an identical pH. This is not the main application of UV-Vis spectrophotometry as the best results in this context are provided by spectroscopic methods considered more effective for the study of the molecular structure of organic compounds (infrared, nuclear magnetic resonance, mass spectrometry, and X-ray diffraction). However, UV-Vis spectrophotometry is a source of relevant supplementary information that helps in the elucidation of molecular structures of drugs, impurities, metabolites, intermediate compounds of degradation, etc. 

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