Redi, MesfinKebede, Tesfaye2018-06-262023-11-092018-06-262023-11-092007-07http://etd.aau.edu.et/handle/12345678/3445This paper mainly tends to explain the dual fluorescence of alizarin and its structures that are responsible for the existence of fluorescence emission spectra different from absorption spectra. And uses structural isomerism (Tautomersim) to explain the dual fluorescence shown by this compound. As well the affect of the PH of the media, polarity of the solvent and hydrogen bond forming tendency of solvents on both absorption and fluorescence emission spectra of alizarin were studied. Four alizarin tautomers were selected for simplicity that may exist in both ground and excited state or only in one of the two states. The structure of this compound is investigated both experimentally and theoretically. Experimentally its absorption, fluorescence emission spectra and 1H NMR were done and computational techniques (HF, DFT and semiemperical) were used to calculate total energy, Gibbs free energy, dipole moment, excitation energy and other molecular parameters. Key words: Alizarin, fluorescence, tautomers, computational, absorption, protic, aprotic and 1H NMRenAlizarinFluorescenceTautomersComputationalAbsorptionProticaprotic and 1H NMR.Thesis