In contrast to the ether bond cleavage, this mechanisms consists of two subsequent steps. In the first step, a hydrogen is transferred from a methyl group to the ipso carbon of the adjacent monomeric unit. The formed biradical can than dissociate in a subsequent reaction to fragments with a quinonemethide and a phenolic structure. The results are summarized in table 3 and displayed in figure 3.Optimized structures can be obtained here:
Step 1 (Hydrogen Transfer): I ---> II(TS) ---> III Step 2 (Ether cleavage): III ---> IV(TS) ---> V
Table 1: Calculated state energies for the 1,5-hydrogen
transfer and the subsequent ether bond cleavage. Energies given in kJ/mol.
Fig. 3: 1,5-Hydrogen Transfer