Directing effects deactivation

Because we have come to associate activating substituents with ortho para directing effects and deactivating substituents with meta the properties of the halogen substituents appear on initial inspection to be unusual... 

Inductive and resonance effects account for the directing effects of substituents as well as for their activating or deactivating effects. Take alkyl groups, for instance, which have an electron-donating inductive effect and are ortho and para directors. The results of toluene nitration are shown in Figure 16.13. 

If the work function is smaller than the ionization potential of metastable state (see. Fig. 5.18b), then the process of resonance ionization becomes impossible and the major way of de-excitation is a direct Auger-deactivation process similar to the Penning Effect ionization a valence electron of metal moves to an unoccupied orbital of the atom ground state, and the excited electron from a higher orbital of the atom is ejected into the gaseous phase. The energy spectrum of secondary electrons is characterized by a marked maximum corresponding to the... 

A wide variety of aromatic compounds can be brominated. Highly reactive ones, such as anilines and phenols, may undergo bromination at all activated positions. More selective reagents such as pyridinium bromide perbromide or tetraalkylammonium tribromides can be used in such cases.18 Moderately reactive compounds such as anilides, haloaromatics, and hydrocarbons can be readily brominated and the usual directing effects control the regiochemistry. Use of Lewis acid catalysts permits bromination of rings with deactivating substituents, such as nitro and cyano. 

It has been observed that, the indirect effect of delta coke on catalyst deactivation, and the direct effect of delta coke on the blocking of acid sites (early) in the riser seems to be a prime factor, which dominates conversion and selectivity effects in a resid type of operation. 

Recent experimental evidence (3, 4) has demonstrated that heparin s anticoagulant effect results from its ability to catalyse the deactivation of several of the clotting factors. Of particular importance and the primary reason for heparin s anticoagulant effect is the drug s ability to deactivate thrombin by catalysing the reaction between thrombin and its inhibitor antithrombin III (AT-III). Because it acts directly to deactivate clotting factors, heparin has a very fast anticoagulant effect. 

Neither Friedel-Crafts alkylation nor acylation works on deactivated rings, and the directing effects are wrong also. 

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