Spectroscopic Studies on the Tautomers of Heptane-2,4,6-trione and Its Methylated Homologues

3,5-Dimethylheptane-2,4,6-trione and 3-methylheptane-2,4,6-trione are synthesized by methylationheptane of-2,4,6-trione via alkali metal enolates or an enamine intermediate of the mother compound. In keto-enol tautomerism, the latter two compounds take triketo-, monoenol-, and bisenol forms, while the first one exists in triketo and monoenol forms, being unable to take a bisenol form. NMR spectra of the tautomers are assigned by combining with IR data. Keto-enol ratio in a range of solution phases at various temperatures are estimated by NMR method and effect of the branched methyl groups upon the keto-enol tautomerism is discussed.