Title

Gas-phase acidities of aryl-substituted fluorinated alkanes. The nature of β-fluorine negative hyperconjugation

Document Type

Article

Publication Date

1-1-2015

Abstract

Gas-phase acidities (GA) of 2-phenyl- and 2-p-nitrophenyl-substituted fluoroalkanes, ArCH R and ArCH(R )R , were calculated at the B3LYP/6-311+G(d,p) level of theory. The GA values of the fluoroalkanes having no fluorine atom at the β-position of the conjugate acid anion center were correlated linearly with the corrected number of fluorine atoms contained in the fluorinated alkyl group (R ), indicating that these acidities were determined by accumulated inductive effect of fluorine atoms. The GA values of ArCH(CF ) 1 and ArCH(C F ) 2 also conformed to the line, indicating negligible or no contribution of β-fluorine negative hyperconjugation to the stability of both carbanions. On the basis of this linear relationship, the extent of β-fluorine negative hyperconjugation involved in the acidity of fluoroalkanes having β-fluorine was evaluated quantitatively. It was concluded that the contribution of β-fluorine negative hyperconjugation to acidity of aryl-substituted fluoroalkanes is complementary to stabilization effects by the aryl group as well as accumulated inductive effect of fluorine atoms contained in the fluorinated alkyl group. 2 f f f f 3 2 2 5 2 1 2

Publication Name

Bulletin of the Chemical Society of Japan

Volume Number

88

First Page

455

Last Page

464

Issue Number

3

DOI

10.1246/bcsj.20140281

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