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The Protonation of Aromatic π Carbocations. The Behavior of 2‐Hydroxy‐ and 9‐Hydroxyphenalenone in Trifluoromethanesulfonic Acid
Author(s) -
Pagni Richard M.,
Smith Robert J.,
Moore Theresa,
Burnett Michael N.
Publication year - 1980
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.198000089
Subject(s) - carbocation , chemistry , protonation , medicinal chemistry , reactivity (psychology) , computational chemistry , organic chemistry , ion , alternative medicine , pathology , medicine
In continuation of work on the protonation of aromatic π carbocations, the behavior of 1,2‐dihydroxyphenalenyl cation ( 7 ) and 1,9‐dihydroxyphenalenyl cation ( 8 ) in CF 3 SO 3 D was investigated. The behavior of carbocation 8 was unexceptional. It underwent a facile exchange at room temperature, with H‐2, H‐5 and H‐8 all exchanging at comparable rates. Carbocation 7 , on the other hand, exchanged at an exceptionally slow rate, even at 100°C. The order of reactivity of the various sites on 7 was found to be H‐3 ≫ H‐5 ⪖ H‐4 ≈ H‐6; H‐7, H‐8 and H‐9 did not exchange. These unusual results are best accommodated by assuming that most, if not all, of the exchange actually occurs on 2‐hydroxyphenalenone ( 9 ) which is present in very low concentration. Hückel calculations support this contention.