DMSO-d6 Solvent Research Articles

Structure of isoniazide hydrazone of 1, 3-diketone derivatives (1, 3-Diketone-INAH) was examined by the use of mass, nuclear magnetic resonance, ultraviolet and infrared spectra. Mass spectra : Parent peak was observed abundanlty in trifluoroacetylacetone (TAA-INAH) but weakly in thenoyltrifluoroacetone (TTA-INAH), and not in benzoyltrifluoroacetone (BFA-INAH) and acetylacetone (AA-INAH). However, M-18 ion was present strongly in BFA-, TTA-, furoyltrifluoroacetone (FTA)-and AA-INAH but weakly in TAA-INAH. These observations suggest that most of isoniazide hydrazone of 1, 3-diketones may be in enol form. Nuclear magnetic resonance : FTA-and TTA-INAH have enol structure in CDCl3. Chemical shift of NH proton is 11.84 ppm and OH proton 4.16 ppm in TTA-INAH. The signal for the OH and CH2 proton in FTA-INAH appeared at 4.11 and 3.48 ppm, respectively. These two hydrazones indicated, however, to hold keto structure in DMSO-D6 solvent (Fig.5-2, Fig.6). Other six compounds are present having mainly keto form in CDCl3. It is demonstrated that plot of the chemical shift of methylene proton against one of imino proton has linear relationship with each other among compounds of six hydrazones substituted alternately with CH3, CF3, and C6H5 in 1, 3-position of diketone group (Fig.2). Ultraviolet : AA-INAH has only one peak at 307 mμin CHCl3 but showed two peaks at 220 and 280 mμ in methanol. FTA-INAH has, however, two peaks in CHCl3, indicating the presence of enol structure. From these ultraviolet and nuclear magnetic resonance spectra, variation of keto-enol sturcture of eight isoniazide hydrazones in various solvents can be elucidated unequivocally. Infrared : Assignments of infrared bands of isoniazide hydrazones of 1, 3-diketone were postulated and their structure was discussed.

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