Fig. 3 in Chemical evolution of the colour systems generated by riccionidin A, 3-deoxyanthocyanidins and anthocyanins

Fig. 3. (a) Representation of the rate constants versus pH of the second step for Oenin 2.5 × 10−5 M, eq. (5); (b) the same for the third step, which is much slower, eq. (7). The rate and equilibrium constants to represent eq. (5) and eq. (7) were taken from reference (Pina et al., 2019); (c) colours of 5.7 × 10−5 M Oenin multistate (1) Flavylium cation at pH = 1.0; (2) quinoidal base immediately after a direct pH jump to pH = 5.0; (3) at the equilibrium for the same pH of (2); (4) the intense blue is given by the anionic form of the quinoidal base as shown immediately after a pH jump to pH = 8.0. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)