ED-diagram

The NFPA 704 System (used at industrial facilities) This system uses a diamond shap>ed diagram divided into four quadrants to identity the health , flammability and reactivity of a chemical. Severity is indicated by numbers 0 to 4, with 4 being the most severe. 

The complete set of interaction sequences incorporated in the fourth-order term for Mfi are accounted for by 96 time-ordei ed diagrams, in the general case, 48 of which are associated with the cooperative mechanism and 48 with the distributive mechanism examples of each type are shown in Fig. 8. The matrix element contribution for the cooperative mechanism corresponding to Fig. 8(a), for example, when evaluated using Eq. (5.7) gives the following result ... 

The ED-diagram results in a straight line passing the zero point with the slope Q11/Q21 (see Fig. 5.6). By these means any reaction can be tested in a simple way for uniformity using diagrams with statistically dependence of the wavelength on. ... 

It has been demonstrated that ED-diagrams always result in zero point straight lines if the rank of Q... 

Even though if in a certain spectral region Just one compound absorbs, the in two columns become equal. This fact proves that one has to examine the ED-diagrams at as many wavelength combinations as possible (see Fig. 5.7). 

Fig. 5.8 is an example of an ED-diagram of a consecutive photoreaction which proceeds according to eq. (3.39) and fulfils eq. (3.40) with <1 [131,143]. The different combinations of wavelengths allow two linear areas to be realsied in which one of the partial steps of reaction dominates. However, the typical slopes of Fig. 2.7 of Section 2.4.2.2 given by... 

If a, and 2 differ, the initial slope in a X-diagram depends on the ratio of a2o/aio. The same is evident for an ED-diagram. Thus the initial slope becomes dependent on concentration for any type of quantum yield. On the other hand if = a, (both photochemical partial reactions start with the same compound) at least one of the quantum yields has to be a function of concentration. Otherwise dx2/dxi becomes constant and jc, and JC2 would linearly depend on each other which is contradictory to the assumption. 

A point of inclination in an ED-diagram requires that the left-hand side of... 

The constant x was defined by eq. (3.40). Since this x does not contain any initial concentrations, the final slope in an ED-diagram will... 

Fig. 5.9. Reduced ED-diagram of the consecutive photoreaction on 2-methyI-anthraquinone in alkaline methanolic solution, NaOH (0.1 moi f ) wavelength of irradiation is 313 nm, the intensity of the light source is / = 1.24 x KT Einstein s" cm", cone. ( ), a, = 5.81 x I(T ...

If the quantum yields are independent of concentration - as has been presumed - then the reduced ED-diagram has to be invariant against dilution since no initial concentrations show up in the differential equations. This can be seen in Rg. 5.9 for two different concentrations. 

For the dependencies on intensity and wavelength in the ED-diagrams the same rules are valid as for K-diagrams. For comparison see Section 5.1.1.2. In Fig. 5.8 the dependence on intensity has been matked, demonstrating that the ED-diagrams do not differ. 

A comparison of the initial slopes shows that as long the first reaction takes place the initial slope of the photoreaction is different from the slope of the thermal reaction. However as long as the second reaction takes place both slopes become the same. Fig. 5.10 gives an ED-diagram of this photoisomerisation. The irradiation was interrupted many times. The slopes of the thermal reactions are parallel to each other, and their slopes differ from the initial slope of the photochemical reaction [145]. 

For this reason the second mechanism is discarded. The ED-diagram accounts for the first mechanism. However, it does not prove it, since the reaction could proceed in a more complicated way. 

If a linear EDQ-diagram intersects the coordinate system at the zero point or is parallel to one of the axes it is called degenerate and does not allow any information on the number of linear independent partial reactions. Under these conditions one of the three becomes zero. In consequence one of the three possible ED-diagrams degenerates to be linear. For example As = Q Q%i Q Q n becomes zero by chance or Qy = = 0 can become... 

Fig. S. 16. ED-diagram of the photoreaction of 2-chIoro-anthraquinone in neutral methanol.

The evaluation of kinetic data is more complicated if an additional thermal reaction is superimposed on the photoreaction. In addition to the ED-diagrams given in Section S.3.3.1 some further examples of kinetic analysis can be given. Typical examples are the reactions of photochromic substances either belonging to the classes of dihydroindolizine derivatives, fulgides, or even azobenzene-derivatives. This thermal step either can be a backward... 

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