Parallel photoreaction including other reactants

In the following examples parallel photoreactions starting from the same initial product but including different reactants are treated. 

Example 3-17 One of the parallel photoreactions includes a photoaddition The photoreaction 

Using reduced degrees of advancement according to Section 2.4.2 the following definitions are taken  

Similar relationships are obtained, if B and D are formed via the triplet A . However, different equations arise if B is formed from the singlet A and D from the triplet A according to 

In the next example both steps of the photochemical reaction include a partner, both being photoaddition reactions. In the case where in both of the reactions the same initial product starts the photoreaction and reacts with the same partner via the same type of excited state, the reactions become uniform, i.e. just one linear independent step is observed. This mechanism can be compared with a thermal reaction discussed in Section 2.4.1.1. 

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