Figure shows the normalised absorbance values of the spectral range of 1820-1630 cm -1 (Fig. ) and 1390-1330 cm -1 (Fig. ) plotted against the reaction time. The spectral range of 1820-1630 cm -1 includes the sum of all carbonyl species, whereas the range of 1390-1330 cm -1 is indicative for phenolic hydroxyl . The aim is to show the time course of the carbonyl species as well as the phenolic OH groups, since these functional groups are relevant for later application purposes. Looking at Figure , without the use of additives (black), the absorption of the carbonyl species increases over time after 5 minutes, but then decreases and remains at one level. A similar behavior can be observed for the experiments with NaOH (red) and SPC (green). The use of basic components such as NaOH favors the formation of quinone-or quinonmethide-like structures by ether cleavage, but is otherwise not strong enough to induce some oxidation processes, which explains the increased but otherwise constant absorption values for the NaOH experiments (red) . The decrease in absorption after 5 minutes of reaction time in the control experiments is presumably caused by advancing rearrangement and some condensation reactions in the molecule, which eliminates carbonyl structural features. After an initial increase in intensity, the absorbance value for the SPC series (green) remains almost the same, while an abrupt increase is observed after 60 minutes. SPC itself reacts alkaline but this basicity may not be sufficient to generate enough possible reactive species for further reaction with the hydrogen peroxide. This ensures that the reaction is slow, and the first signs of oxidation do not appear until after 45 minutes of reaction time.