pK_a Determination of Weak Bases by Fluorine-19 Nuclear Magnetic Resonance Spectrometry.

Carboxylic acid ionization constants by19F NMR spectroscopy

“…The chemical shift ( F ) range of a 19 F NMR signal is intrinsically very wide, and therefore the fluorine nucleus is an excellent, highly sensitive probe of its environment. This fact was used more than 35 years ago for pK a determinations of p-fluoroacetophenone (C-H acidity) and p-fluorobenzamide (N-H acidity), 7 and as recently as 1998 for subtle changes of F arising from solvent-induced isotope shifts due to enrichment of water with H 2 18 O. 8 The literature provides a number of examples in which 19 F NMR spectroscopy was used to study the ionization of protonated amines containing fluorine.…”

Styrene and styrene dimer derivatives, cyclohexene, tert-butylbenzene and cumene as test reactions for acid strength measurements of crystalline and amorphous silica-aluminas, sulfated oxides and Amberlyst

“…Microcalorimetry [21], TPD [22], adsorption [23] or calorimetric titration [24,25] have been commonly used. The initial heat of ammonia adsorption at 423 K [21,26], activation energy of ammonia desorption [16] and differential heat of ammonia adsorption [22] can be applied in the classification of solids, especially zeolites, with respect to their acid strength:…”

Nuclear Magnetic Resonance Studies of Ions in Pure and Mixed Solvents

“…Utilizing the large differences in the F19 nmr lines for the protonated and unprotonated forms of fluorobenzene derivatives, Taft and Levins (338) obtained quantitative pK& values for the equilibrium reactions of these compounds. and -6.06 determined by ultraviolet studies in aqueous sulfuric acid solution (99,333).…”