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5784286 
Journal Article 
Strong acidity of some polycyclic aromatic compounds annulated to a cyclopentadiene moiety and their cyano derivatives - A density functional B3LYP study 
Vianello, R; Maksic, ZB 
2005 
Yes 
European Journal of Organic Chemistry
ISSN: 1434-193X
EISSN: 1099-0690 
Wiley-VCH Verlag 
2005 
16 
3571-3580 
English 
WOS:000231337000021 
The 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 of their polycyano derivatives is examined in the gas phase and in DMSO by the DFT-B3LYP methods. It is shown that the parent hydrocarbons exhibit modest acidities, whereas a 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 a ketene imine C=C=NH functionality. The origin of their highly pronounced acidity is identified as a very strong anionic resonance effect efficiently assisted by a large number of CN groups in a concerted manner. It is stressed that the polycyanated anions are very stable and have a 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. © Wiley-VCH Verlag GmbH & Co. KGaA, 2005. 
anionic resonance; acidity; polarized continuum model; substituent effects; superacidic systems