Review Article
Protonation Equilibria of Biologically Active Ligands in Mixed Aqueous Organic Solvents
Table 9
Protonation constants of
α-amino acid esters in water-1,4-dioxane mixtures
Temp. = 25°C and
mol·dm
−3 NaCl
a.
| | Esters | | | Water | 20% D—80% W
() | 40% D—60% W
() | 60% D—40% W
() | | | | |
| | GlyO-Me | 1 | 1 | 7.67 | 7.47 | 7.18 | 6.85 | | GlyO-t-Bu | 1 | 1 | 8.38 | 8.21 | 7.91 | 6.97 | | ValO-Me | 1 | 1 | 7.53 | 7.38 | 7.09 | 6.08 | | ValO-Et | 1 | 1 | 8.86 | 8.01 | 7.15 | 6.58 | | ValO-t-Bu | 1 | 1 | 9.05 | 8.54 | 7.71 | 7.13 | | SerO-Me | 1 | 1 | 7.10 | 6.99 | 6.69 | 6.61 | | SerO-Et | 1 | 1 | 7.46 | 7.25 | 6.84 | 6.79 | | LeuO-Me | 1 | 1 | 7.66 | 7.47 | 7.19 | 6.32 | | LeuO-Et | 1 | 1 | 7.75 | 7.78 | 7.31 | 6.73 | | LeuO-t-Bu | 1 | 1 | 7.89 | 8.04 | 7.60 | 6.95 | | PheO-Me | 1 | 1 | 7.11 | 6.66 | 6.42 | 6.01 | | PheO-Et | 1 | 1 | 8.12 | 7.24 | 6.81 | 6.24 | | PheO-t-Bu | 1 | 1 | 8.26 | 7.39 | 6.96 | 6.64 |
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Note. D = dioxane, W = water; adata taken from ref. [44]. corresponds to 11 species (i.e., L− + H+ LH).
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