A large variety of nucleophilic carbon-centered radicals, starting from several of the most important classes of organic compounds (alkanes, alkenes, alkylaromatics, alcohols, aldehydes, ketones, ethers, carboxylic acids, amines, amides, alkyl halides etc.), have been utilized for the highly selective substitution of protonated heteroaromatic bases. The parallelism with the Friedel-Crafts aromatic substitution is related to the fact that more stable is a carbonium ion more nucleophilic will be the corresponding radical. Thus the radicals corresponding to all the electrophilic species of the Friedel-Crafts reaction can be utilized for the selective substitution of protonated heteroaromatic bases with opposite reactivity and selectivity. It is shown how charged species greatly affect the polar effect in the free-radical reactions and this last is at the origin of the synthetic success.