Modeling solubility and acid–base properties of some amino acids in aqueous NaCl and (CH3)4NCl aqueous solutions at different ionic strengths and temperatures

Bretti, Clemente; Giuffrè, Ottavia; Lando, Gabriele; Sammartano, Silvio

doi:10.1186/s40064-016-2568-8

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Table 1 Ionic strength and temperature dependence parameters of protonation constants Eq. (10) at T = 298.15 K and at infinite dilution for l-glycine, l-alanine, l-valine, l-leucine, l-serine and l-phenylalanine in NaCl and (CH₃)₄NCl

From: Modeling solubility and acid–base properties of some amino acids in aqueous NaCl and (CH₃)₄NCl aqueous solutions at different ionic strengths and temperatures

Parameter	Gly	Ala	Val	Leu	Ser	Phe	Average
Log \( {\text{K}}_{1}^{\text{H0}} \)	9.777 ± 0.004^a	9.912 ± 0.012^a	9.730 ± 0.008^a	9.777 ± 0.005^a	9.255 ± 0.009^a	9.257 ± 0.006^a	9.618 ± 0.287^a, 9.80 ± 0.08^c
Log \( {\text{K}}_{2}^{\text{H0}} \)	2.329 ± 0.007	2.365 ± 0.015	2.286 ± 0.005	2.321 ± 0.007	2.162 ± 0.005	2.144 ± 0.017	2.267 ± 0.093, 2.32 ± 0.03^c
\( \Delta {\varepsilon}_{ 1}^{\infty} \) (NaCl)	0.190 ± 0.016	0.195 ± 0.012	0.189 ± 0.082	0.260 ± 0.012	0.187 ± 0.005	0.162 ± 0.047	0.197 ± 0.033
\( \Delta {\varepsilon}_{ 1}^{0} \) (NaCl)	0.311 ± 0.020	0.35 ± 0.037	0.395 ± 0.068	0.354 ± 0.014	0.329 ± 0.019	0.332 ± 0.049	0.345 ± 0.029
\( \Delta {\varepsilon}_{ 2}^{\infty} \) (NaCl)	0.098 ± 0.010	0.114 ± 0.007	0.089 ± 0.180	0.177 ± 0.007	0.096 ± 0.009	0.241 ± 0.053	0.136 ± 0.061
\( \Delta {\varepsilon}_{ 2}^{ 0} \) (NaCl)	0.093 ± 0.023	0.091 ± 0.031	0.070 ± 0.066	0.069 ± 0.020	0.061 ± 0.029	0.121 ± 0.075	0.084 ± 0.022
\( \Delta {\varepsilon}_{ 1}^{\infty} \) ((CH₃)₄NCl)	0.048 ± 0.009	0.034 ± 0.016	0.033 ± 0.012	0.055 ± 0.006	0.051 ± 0.016	0.015 ± 0.022	0.039 ± 0.015
\( \Delta {\varepsilon}_{ 1}^{ 0} \) ((CH₃)₄NCl)	0.269 ± 0.030	0.275 ± 0.051	0.262 ± 0.032	0.276 ± 0.019	0.277 ± 0.044	0.247 ± 0.055	0.268 ± 0.012
\( \Delta {\varepsilon}_{ 2}^{\infty} \) ((CH₃)₄NCl)	0.110 ± 0.008	0.073 ± 0.007	0.092 ± 0.015	0.091 ± 0.006	0.119 ± 0.024	0.146 ± 0.018	0.105 ± 0.026
\( \Delta {\varepsilon}_{ 2}^{ 0} \) ((CH₃)₄NCl)	0.079 ± 0.020	0.082 ± 0.033	0.060 ± 0.057	0.066 ± 0.034	0.102 ± 0.055	0.091 ± 0.063	0.080 ± 0.016
\( \Delta {{H}}_{ 1}^{ 0} \)	−44.33 ± 0.03^b	−44.20 ± 0.03^b	−44.46 ± 0.09^b	−45.25 ± 0.09^b	−42.78 ± 0.05^b	−44.06 ± 0.15^b	−44.2 ± 0.8^b
\( \Delta {{H}}_{ 2}^{ 0} \)	−3.99 ± 0.01	−2.63 ± 0.02	−0.33 ± 0.12	−1.77 ± 0.16	−4.47 ± 0.20	−1.64 ± 0.29	−2.5 ± 1.6
\( \Delta {\varepsilon}_{ 1}^{\prime} \)	−0.96 ± 0.03	−2.35 ± 0.70	−1.73 ± 0.34	−2.76 ± 0.05	8.8 ± 0.6	−1.32 ± 0.12	−0.1 ± 4.4
\( \Delta {\varepsilon}_{ 2}^{\prime} \)	−0.85 ± 0.03	−1.75 ± 0.38	1.82 ± 3.00	−0.82 ± 0.05	7.3 ± 1.6	−2.16 ± 0.12	0.6 ± 3.6
\( \Delta {\text{C}}_{\text{p1}} \)	41 ± 2	41 ± 2	39 ± 2	39 ± 3	41 ± 2	38 ± 3	40 ± 1
\( \Delta {\text{C}}_{\text{p2}} \)	136 ± 1	108 ± 5	150 ± 4	131 ± 7	141 ± 7	138 ± 5	134 ± 14
\( \Delta {\varepsilon}_{ 1}^{\prime} \) ((CH₃)₄NCl)				−0.09 ± 0.06
\( \Delta {\varepsilon}_{ 2}^{\prime} \) ((CH₃)₄NCl)				−1.78 ± 0.15

^a ± 95 % CI
^b in kJ mol⁻¹
^c average among glycine, alanine, valine and leucine

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