Regarding point (i): When choosing the reaction and the substrate, one needs to consider the possibility of detecting both kinetic and thermodynamic effects; it is reasonable to vary the size and the molecular geometry of the substrate, and to trace the effect of substrate adsorption. Thus, if the above series is considered, it would be reasonable to take for comparison r ea dily a ds or bing halogen derivatives RX with X= -Cl, -Br, -I, as well as allylic analogues CH 2 =CH-CD 2 X: These are molecules with a smaller size, they could be associated with protecting groups, thereby providing ample opportunities to vary the size, spatial structure, working potential region, etc. (cf. ).