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Solvent and Substituent Effects in the Solvolysis of 9‐Aryl‐9‐bromofluorenes
Author(s) -
Liu KwangTing,
Lin YenShyi
Publication year - 2000
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.200000007
Subject(s) - solvolysis , chemistry , substituent , electrophile , aryl , reaction rate constant , delocalized electron , solvent , computational chemistry , medicinal chemistry , organic chemistry , alkyl , kinetics , catalysis , physics , quantum mechanics , hydrolysis
The solvolysis of eight 9‐aryl‐9‐bromofluorenes ( 6b∼6i ) in a variety of solvents were studied. Correlation analysis using single‐parameter Grunwald‐Winstein equation (Eqn. 1) with different Y scales showed good linearity ( R ≥ 0.98) for most cases if Y xBnBr was employed. Linear relationships were observed from Hammett‐type analysis of logarithm of rate constants using Brown‐Okamoto σ + constants (Eqn. 3), although inverse order of k ( p ‐CF 3 )/ k ( m ‐ CF 3 ) was realized in a number of cases. The ρ values were found to vary slightly with different solvent systems. Calculated atomic charge reveals the similarity between 9‐phenyl‐9‐fluorenyl cation ( 7 ) and triphenylmethyl cation ( 8 ). An extended charge delocalization throughout the fluorenyl ring led to the conclusion of the insignificance of antiaromaticity, which was in harmony with that obtained in previous studies. The variation of relative k Br / k Cl rate ratios was attributed to the electrophilic pull by solvents in solvolysis.