The 4-Fluorophenol Hydrogen-Bond Basicity Scale

3 The 4-Fluorophenol Hydrogen-Bond Basicity Scale 4.3.1 Definition 

Let (Equation 4.7) be the equilibrium constant for the hydrogen bonding of 4-fluorophenol to a variety of Lewis bases in CCI4 at 25 °C, where the subscript c indicates that the concentration scale is used  

Currently, the lowest and highest primary Kc values are 0.14 1 mol for the very weak n base 2,3-dimethylbut-2-ene [75] and 120 0001 mol for the tetrabutylammonium cyanate ion pair [93], respectively. A secondary /sfo value of 288 400 1 mol has been reached for trimethylamine A-oxide [94]. Since /sfo values vary over many orders of magnitude, it is more convenient to use a logarithmic scale. 

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