A series of new azo dyes derived from cyclohexane- 1,3-dione have been synthesized and studied as regards the existence of prototropic tautomerism both in gas phase and in solution. The calculated equilibrium constants predicted by DFT method are in agreement with the NMR experimental results, predicting the existence of all newly studied dyes predominantly or completely in their hydrazone forms. The positions of 1H signals in NMR spectra compare qualitatively with those predicted computationally at the GIAO/DFT level of theory. Different bands observed in electronic absorption spectra have been assigned to the proper electronic transitions. The new band displayed by compound 5 in proton accepting solvents was regarded as a result of ionization. This characteristic band could be useful if the compound was used as analytical indicator. Analysis of electronic absorption spectra confirms the conclusions drawn from calculations and examination of 1H NMR as well as FT-IR spectra.