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The first automated 470.59 MHz 19 F NMR‐controlled titration: dissociation constants and ion‐specific chemical shifts of 2‐amino‐4‐fluoro 2‐methylpent‐4‐enoic acid
Author(s) -
Uhlemann C. E.,
Pfaff C. G.,
Hägele G.,
Laue K. W.,
Lübke M.,
Haufe G.
Publication year - 2002
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1058
Subject(s) - chemistry , chemical shift , deprotonation , titration , dissociation constant , analytical chemistry (journal) , ion , acid dissociation constant , dissociation (chemistry) , proton nmr , nuclear magnetic resonance spectroscopy , acetic acid , equilibrium constant , nuclear chemistry , stereochemistry , aqueous solution , organic chemistry , receptor , biochemistry
2‐Amino‐4‐fluoro‐2‐methylpent‐4‐enoic acid, obtained as a 1 : 1 salt with trifluoro‐acetic acid, was characterized by 1 H and 19 F high‐resolution NMR spectroscopy. High‐precision potentiometry led to the dissociation constants p K a 1= 1.879 and p K a 2= 9.054. The first automated 470.59 MHz 19 F NMR‐controlled titration yielded the dynamic chemical shift 〈δ F 〉 as a function of pcH or τ and the ion‐specific chemical shifts: δ F (H 2 L + ) = −94.81 ppm, δ F (HL) = −94.21 ppm, δ F (L − ) = −92.45 ppm. The deprotonation gradients were found to be Δ 1 = −0.60 ppm and Δ 2 = −1.76 ppm. Copyright © 2002 John Wiley & Sons, Ltd.