title: Chemistry and photochemistry of 2,6-bis(2-hydroxybenzilidene)cyclohexanone. An example of a compound following the anthocyanins network of chemical reactions.
abstract: The kinetics and thermodynamics of the 2,6-bis(2-hydroxybenzilidene)cyclohexanone chemical reactions network was studied at different pH values using NMR, UV-vis, continuous irradiation, and flash photolysis. The chemical behavior of the system partially resembles anthocyanins and their analogue compounds. 2,6-Bis(2-hydroxybenzilidene)cyclohexanone exhibits a slow color change from yellow to red styrylflavylium under extreme acidic conditions. The rate constant for this process (5 × 10(-5) s(-1)) is pH independent and controlled by the cis-trans isomerization barrier. However, the interesting feature is the appearance of the colorless compound, 7,8-dihydro-6H-chromeno[3,2-d]xanthene, isolated from solutions of acid to neutral range, characterized by (1)H NMR and single crystal X-ray diffraction. Light absorption by 2,6-bis(2-hydroxybenzilidene)cyclohexanone solutions immediately after preparation exclusively results in cis-isomer as photoproduct, which via hemiketal formation yields (i) red styrylflavylium by dehydration under extremely acidic solutions (pH < 1) and (ii) colorless 7,8-dihydro-6H-chromeno[3,2-d]xanthene by cyclization in solutions of acid to neutral range.
authors: REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa , 2829-516 Monte de Caparica, Portugal.
authors: Artur J
authors: AJ
authors: Moro
authors: Ana-Maria
authors: AM
authors: Pana
authors: Liliana
authors: L
authors: Cseh
authors: Otilia
authors: O
authors: Costisor
authors: Jorge
authors: J
authors: Parola
authors: L
authors: L
authors: Cunha-Silva
authors: Rakesh
authors: R
authors: Puttreddy
authors: Kari
authors: K
authors: Rissanen
authors: Fernando
authors: F
authors: Pina
mesh_terms: D000872:Anthocyanins / Q000737:chemistry*; D001593:Benzyl Compounds / Q000737:chemistry*; D003512:Cyclohexanones / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D015394:Molecular Structure; D055668:Photochemical Processes
chemical_list: C000597653:2,6-bis(2-hydroxybenzilidene)cyclohexanone; D000872:Anthocyanins; D001593:Benzyl Compounds; D003512:Cyclohexanones