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HERO ID
5784286
Reference Type
Journal Article
Title
Strong acidity of some polycyclic aromatic compounds annulated to a cyclopentadiene moiety and their cyano derivatives - A density functional B3LYP study
Author(s)
Vianello, R; Maksic, ZB
Year
2005
Is Peer Reviewed?
Yes
Journal
European Journal of Organic Chemistry
ISSN:
1434-193X
EISSN:
1099-0690
Publisher
Wiley-VCH Verlag
Volume
2005
Issue
16
Page Numbers
3571-3580
Language
English
DOI
10.1002/ejoc.200500153
Web of Science Id
WOS:000231337000021
URL
http://
://WOS:000231337000021
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Abstract
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.
Keywords
anionic resonance; acidity; polarized continuum model; substituent effects; superacidic systems
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