24533-03-7Relevant academic research and scientific papers
Structural transformations of the synthetic salt 4', 7-dihydroxyflavylium chloride in acid and basic aqueous solutions. Part 1 - Ground state
Pina, Fernando,Benedito, Lina,Melo, Maria Joao,Parola,Lima, Joao C.,Macanita, Antonio L.
, p. 111 - 118 (2007/10/03)
A complete study of the structural pH dependent transformations of the synthetic flavylium salt 4',7-dihydroxyflavylium chloride (DHF). occurring in aqueous solutions, including the basic region, is described. The kinetic study of the transformations occuring in acidic media (quinoidal base (A) ? flavylium cation (AFT) ? hemiacetal (B) ? cis-chalcone (Ctrans) ? trans-chalcone (Ctrans)) allowed to conclude that the cis-trans isomerization is faster than the tautomerization and the hydration processes, which is unique in the anthocyanins family. Results obtained with the parent compound 4",7dimethoxyflavylium chloride (DMF) with relevance to this study are also presented. In equilibrated basic solutions the existence of acid-base equilibria involving the trans-Chalcone (Ctrans) and its conjugated bases. (C transand C2trans), was detected. Freshly prepared solutions at pH >7 show also the presence of a transient species identified as the ionized quinoidal base (A-), which is almost completely converted into C2-trans with a pH dependent rate constant. Springer-Verlag Iherica 1997.
Hydrolysis of Benzopyrylium Dyes - An Application of the Concept of Chemical Hardness
Lietz, Heike,Haucke, Guenter,Czerney, Peter,John, Birgit
, p. 725 - 730 (2007/10/03)
A systematic study on the relationship between the substitution pattern, the pKa values, and spectral properties of flavylium cations and the respective-(CH2)2-bridged analoga (5,6-dihydrobenzo[c]xanthylium cations) is given in order to find rules concerning their spectral behaviour and their chemical reactivity. Our results show that the concept of chemical hardness can explain the different reactivity of 4′- and 7-substituted flavylium ions against HO-. The pKa values of these species, which can act as a measure of reactivity with respect to a nucleophile, correlate linearly with the absolute hardness calculated from half the energy gap between the frontier orbitals. Since the longest-wavelength UV/VIS absorption maximum is mainly determined by the HOMO-LUMO transition, an analogous linear correlation is obtained between the spectral 0-0 transition and the pKa value. Deviations from these correlations are assumed to be due to steric effects.
Ortho Effect in the Fragmentation of 2-Acetoxychalcones under Electron Impact
Mentlein, Rolf,Vowinkel, Erich
, p. 330 - 333 (2007/10/02)
2-Acetoxychalcones decompose under electron impact conditions by loss of an acetoxy fragment to form flavylium ions.The effect is restricted to the ortho position and is reduced after hydrogenation of the chalcone double bond.The intense flavylium ion originates as shown by specific labelling with 18O-from two different fragmentation lines: (a) direct loss of an acetoxy radical by cleavage of the phenolic Ar-O bond and (b) sequential elimination of ketene and a hydroxy radical.
The Reactions of 2-Phenyl-2H-1-benzopyrans and 2-Phenyl-4H-1-benzopyrans with Lead(IV) Acetate
Kurosawa, Kazu,Yamaguchi, Katsutoshi,Nagata, Yasuyuki,Ohki, Hisatake
, p. 1769 - 1770 (2007/10/02)
The reactions of 7-methoxy-2-phenyl-2H-1-benzopyran and 7-methoxy-2-phenyl-4H-1-benzopyran with lead(IV) acetate gave 2-benzoyl-6-methoxybenzofuran and 6-acetoxy-3-methoxy-6-(3-oxo-3-phenyl-1-propenyl)-2,4-cyclohexadien-1-one.The reactions of 7-methoxy-2-
