Kinetic and thermodynamic study of 2′-hydroxy-8-methoxyflavylium. Reaction network interconverting flavylium cation and flavanone?

RSC Advances Pub Date: 2013-04-12 DOI: 10.1039/C3RA40846A

Abstract

2′-Hydroxyflavylium and 2′-hydroxyflavanone derivatives can be interconverted by a precise sequence of pH jumps, through the respective intermediate (mono) ionized trans-chalcones. In acidic and neutral media, the well known network of chemical reactions involving flavylium cation, quinoidal base, hemiketal, and cis and trans chalcones is established. In the pH range 8 < pH < 10, the chalcone (Ct) deprotonates and evolves to the formation of a flavanone (F). At higher pH values, the di-ionized trans-chalcone is the stable species, formed from the flavylium cation. Acidification of the di-ionized trans-chalcone gives the flavylium cation or the flavanone, via the mono-ionized trans-chalcone, respectively at pH < 1 and pH ≈ 9. In contrast with the chalcones, the flavanone once formed is stable even in acidic media. However, under strongly basic conditions, it leads back to the di-ionized trans-chalcone, the most stable species at more basic pH values, and the reactions leading to Ct?, F, Ct2?, Ct?, constitute a one direction cycle for interconversion of these species.

Graphical abstract: Kinetic and thermodynamic study of 2′-hydroxy-8-methoxyflavylium. Reaction network interconverting flavylium cation and flavanone
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