Electrophilic active ingredients

Bronopol, like the majority of electrophilic active ingredients, has a slow microbicidal effect Bronopol concentrations 2-4 times higher than the MIC in Table 18 take as long as 24 h to display bactericidal activity. 

Polymeric quaternary ammonium salts are the result of reactions between nucleophilic monoamines or diamines and electrophilic di-halo compounds (Renbaum, 1973). They can be further cross-linked with ammonia, ethylenediamine or other reactive amines. Generally the polymeric QACs are not isolated but produced as viscous solutions containing 50-60% active ingredient. The molecular weights of linear polymeric QACs vary between 3000 and 10000 and 30000 and 50000 for cross-linked compounds. 

Another group of active ingredients to be used in slimicides and algicides for cooling waters belongs to the electrophilic active microbicides ... 

The electrophilic active compound impresses by its activity against slime forming microorganisms. Hence it has been an active ingredient in non-presistant slimicides for use preponderantly in the paper industry. 

In 1998 chemistry suddenly appeared in the media in an exceptional way. Normally not a favourite of TV or the newspapers, chemistry produced a story with all the right ingredients— sex, romance, human ingenuity—and all because of a pyrazole. In the search for a heart drug, Pfizer uncovered a compound that allowed impotent men to have active sex lives. They called it Viagra. The molecule contains a sulfonamide and a benzene ring as well as the part that interests us most—a bicyclic aromatic heterocyclic system of a pyrazole fused to a pyrimidine. We shall discuss in detail how Pfizer made this part of the molecule and just sketch in the rest. The sulfonamide can be made from the sulfonic acid that can be added to the benzene ring by electrophilic aromatic sulfonation (Chapter 21). 

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