Naslov
Strong acidity of some polycyclic aromatics annelated to the cyclopentadiene moiety and their cyano derivatives - A density functional B3LYP study

Autori
Vianello, Robert ; Maksić, Zvonimir

Izvornik
European journal of organic chemistry (1434-193X) 16 (2005); 3571-3580

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
anionic resonance; acidity; polarized continuum model; substituent effects; superacidic systems

Sažetak
Acidity of the parent 1H-benz[f]indene (1a), 1H-benz[e]indene (2a), 1H-benz[fg]acenaphthylene (3a) and 1H-cyclopenta[l]phenanthrene (4a) and their polycyano derivatives is examined in the gas-phase and DMSO by the DFT-B3LYP methods. It is shown that pure hydrocarbons exhibit modest acidities, whereas dramatic increase in acidity is observed upon multiple cyanation leading to hyperstrong neutral organic superacids. It is found that polycyano derivatives undergo prototropic tautomerism with a consequence that the most stable tautomer contains keteneimine C=C=NH functionality. The origin of their highly pronounced acidity is identified as a very strong anionic resonance effect, cooperatively and efficiently assisted by a large number of CN groups. It is stressed that the polycyanated anions are very stable and have highly dispersed negative charge, which should lead to a low nucleophilicity and weak coordinating properties, thus making them potentially very useful in academic research and technological applications.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA