Densities and Viscosities of Amino Acid + Xylitol + Water Solutions at

Article pubs.acs.org/jced

Densities and Viscosities of Amino Acid + Xylitol + Water Solutions at 293.15 ≤ T/K ≤ 323.15 Chunying Zhu,* Xiaofen Ren, and Youguang Ma* State Key Laboratory of Chemical Engineering, Collaborative Innovation Center of Chemical Science and Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, P. R. China

ABSTRACT: Densities (ρ) and viscosities (η) of aqueous xylitol solutions with glycine, L-alanine, L-valine, L-threonine, or L-arginine were measured at T = (293.15 to 323.15) K under atmospheric pressure. The density values were utilized to further calculate the apparent molar volume (Vφ), the limiting partial molar volumes of amino acids (Vφ0), the limiting partial molar volumes of transfer (ΔtrVφ0) and the interaction coefficients Vab, Vabb, Vabbb. The viscosity data were used to obtain viscosity B-coefficient, the free energies of activation per mole of solvent (Δμ10≠) and solute (Δμ20≠). The limiting partial molar volumes of transfer and the free energies of activation per mole of both solvent (Δμ10≠) and solute (Δμ20≠) were analyzed based on the cosphere overlap model and transition state theory, respectively. The hydration number of amino acid was determined using the obtained limiting partial molar volume and viscosity B-coefficient.

1. INTRODUCTION Protein is an important component of all living organisms and the material basis of life activity and morphological structure. However, it is very difficult to directly study the nature and function of protein due to its inherent complexity in construction and composition, thus some model compounds like amino acid and peptide are usually utilized to investigate the physical and chemical properties of protein. The research on the thermodynamic behavior of amino acid solution is indispensable for exploring the stability mechanism of protein in the life process. Many previous studies have proven that polyol and sugar could stabilize the native conformation of spherical protein and remarkably affect their denaturalization, solubility, and folding/ unfolding behaviors, and the stability mechanism of the protein is a balance between the nonpolar repulsive force and the attractive force of surface polarity.1,2 The presence of sugar and polyol could enhance the hydrophobic effect between various protein molecules. For polyols, the ability to stabilize protein depends dramatically on their hydroxyl number and configuration.3−5 Up to now, the understanding in the mechanism of protein stabilization remains still far from sufficient. With the growth of the living standard of human beings, the food with functional ingredients receives increasing attention in recent years. For instance, the functional sugar alcohol as a polyol has been widely used as a new type of artificial nutrition © XXXX American Chemical Society

sweetener with the low calorie. Although the thermodynamic properties of the amino acid in polyol solutions have been investigated extensively,6−9 the study on that of the amino acid in sugar alcohol aqueous solution is still lacking. Table 1. Specification of Studied Chemicals mass fraction puritya

molar mass/g·mol−1

source

CAS No.

xylitol

≥0.99

152.15

87-99-0

glycine

≥0.995

75.07

L-alanine

≥0.99

89.09

L-valine

≥0.99

117.15

L-threonine

≥0.99

119.13

L-arginine

≥0.99

174.20

Aladdin Chemical Reagent Co., Ltd. Aladdin Chemical Reagent Co., Ltd. Aladdin Chemical Reagent Co., Ltd. Aladdin Chemical Reagent Co., Ltd. Aladdin Chemical Reagent Co., Ltd. Aladdin Chemical Reagent Co., Ltd.

chemical name

a

56-40-6 56-41-7 72-18-4 72-19-5 74-79-3

Declared by the supplier.

Received: August 29, 2016 Accepted: December 16, 2016

A

DOI: 10.1021/acs.jced.6b00766 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

Table 2. Densities (ρ), Viscosities (η) of Glycine, L-Alanine, L-Valine, L-Threonine and L-Arginine in Xylitol Aqueous Solutions at Temperature T = (293.15, 303.15, 313.15 and 323.15) K and Pressure p = 101.3 kPaa T/K = 293.15 ma mol·kg

ρ

C −1

mol·L

−1

T/K = 303.15 η

−3

g·cm

mPa·s

0.0000 0.1001 0.2000 0.3000 0.4000 0.5000 0.6001 0.7000

0.0000 0.1004 0.1999 0.2986 0.3963 0.4933 0.5894 0.6845

1.00815 1.01133 1.01446 1.01753 1.02056 1.02353 1.02645 1.02931

1.079 1.090 1.101 1.114 1.128 1.142 1.158 1.174

0.0000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000

0.0000 0.1013 0.2018 0.3013 0.4000 0.4978 0.5947 0.6907

1.01764 1.02077 1.02385 1.02689 1.02988 1.03284 1.03575 1.03863

1.161 1.173 1.186 1.200 1.215 1.232 1.249 1.266

0.0000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000

0.0000 0.1022 0.2035 0.3040 0.4034 0.5020 0.5998 0.6965

1.02671 1.02981 1.03287 1.03587 1.03882 1.04173 1.04459 1.04739

1.250 1.265 1.280 1.295 1.313 1.330 1.350 1.369

0.0000 0.1001 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000

0.0000 0.1032 0.2053 0.3065 0.4067 0.5061 0.6046 0.7021

1.03541 1.03848 1.04150 1.04446 1.04737 1.05023 1.05304 1.05580

1.348 1.361 1.376 1.394 1.413 1.432 1.454 1.477

0.0000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000

0.0000 0.1039 0.2069 0.3088 0.4099 0.5101 0.6093 0.7076

1.04378 1.04682 1.04980 1.05273 1.05562 1.05844 1.06122 1.06394

1.443 1.460 1.479 1.500 1.524 1.548 1.577 1.605

0.0000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000

0.0000 0.1002 0.1992 0.2970 0.3936 0.4891 0.5834 0.6766

1.00815 1.01098 1.01376 1.01649 1.01917 1.02179 1.02438 1.02691

1.079 1.099 1.123 1.149 1.179 1.209 1.242 1.273

0.0000 0.1000

0.0000 0.1011

1.01764 1.02042

1.161 1.184

ρ

T/K = 313.15 η

−3

g·cm

mPa·s

Glycine in Xylitol Aqueous Solution mb = 0.2000 mol·kg−1 1.00542 0.855 1.00856 0.864 1.01164 0.873 1.01467 0.884 1.01765 0.894 1.02058 0.906 1.02346 0.919 1.02629 0.932 mb = 0.4000 mol·kg−1 1.01474 0.916 1.01782 0.926 1.02085 0.937 1.02384 0.949 1.02680 0.961 1.02971 0.974 1.03258 0.988 1.03541 1.001 mb = 0.6000 mol·kg−1 1.02367 0.981 1.02672 0.993 1.02972 1.005 1.03268 1.019 1.03558 1.031 1.03844 1.045 1.04125 1.060 1.04401 1.076 mb = 0.8000 mol·kg−1 1.03222 1.059 1.03525 1.071 1.03822 1.082 1.04115 1.097 1.04402 1.112 1.04685 1.128 1.04963 1.145 1.05236 1.161 mb = 1.0000 mol·kg−1 1.04041 1.128 1.04341 1.142 1.04635 1.158 1.04925 1.175 1.05210 1.194 1.05490 1.213 1.05765 1.234 1.06035 1.256 L-Alanine in Xylitol Aqueous Solution mb = 0.2000 mol·kg−1 1.00542 0.855 1.00821 0.871 1.01096 0.889 1.01365 0.909 1.01629 0.931 1.01887 0.953 1.02142 0.978 1.02392 1.004 mb = 0.4000 mol·kg−1 1.01474 0.916 1.01747 0.935 B

ρ g·cm

T/K = 323.15 η

−3

ρ

η −3

mPa·s

g·cm

mPa·s

1.00185 1.00495 1.00799 1.01099 1.01393 1.01683 1.01968 1.02247

0.697 0.705 0.712 0.721 0.731 0.740 0.751 0.762

0.99756 1.00062 1.00363 1.00659 1.00951 1.01238 1.01522 1.01801

0.582 0.589 0.596 0.603 0.611 0.619 0.627 0.637

1.01107 1.01411 1.01710 1.02006 1.02299 1.02587 1.02873 1.03154

0.744 0.752 0.762 0.772 0.782 0.792 0.804 0.815

1.00660 1.00960 1.01257 1.01551 1.01842 1.02130 1.02414 1.02696

0.617 0.625 0.632 0.640 0.649 0.657 0.667 0.677

1.01985 1.02286 1.02582 1.02874 1.03162 1.03445 1.03725 1.03999

0.794 0.804 0.814 0.825 0.837 0.849 0.860 0.872

1.01535 1.01833 1.02127 1.02417 1.02703 1.02984 1.03263 1.03538

0.657 0.665 0.674 0.683 0.693 0.702 0.712 0.722

1.02828 1.03126 1.03420 1.03709 1.03995 1.04275 1.04550 1.04822

0.851 0.861 0.871 0.882 0.894 0.906 0.920 0.934

1.02370 1.02666 1.02957 1.03244 1.03528 1.03807 1.04083 1.04355

0.701 0.709 0.718 0.728 0.738 0.748 0.759 0.770

1.03638 1.03934 1.04225 1.04512 1.04795 1.05072 1.05345 1.05614

0.904 0.916 0.930 0.944 0.959 0.974 0.991 1.008

1.03165 1.03458 1.03746 1.04031 1.04312 1.04588 1.04861 1.05130

0.741 0.753 0.762 0.774 0.787 0.799 0.813 0.827

1.00185 1.00461 1.00733 1.00999 1.01261 1.01518 1.01771 1.02021

0.697 0.709 0.723 0.738 0.755 0.773 0.792 0.810

0.99756 1.00028 1.00296 1.00560 1.00821 1.01076 1.01329 1.01577

0.582 0.591 0.602 0.614 0.627 0.641 0.656 0.670

1.01107 1.01376

0.744 0.758

1.00660 1.00927

0.617 0.628



Article

Table 2. continued T/K = 293.15 ma mol·kg

ρ

C −1

mol·L

−1

T/K = 303.15 η

−3

g·cm

mPa·s

0.2000 0.3000 0.4000 0.5000 0.6000 0.7000

0.2010 0.2997 0.3972 0.4935 0.5887 0.6827

1.02314 1.02582 1.02844 1.03104 1.03356 1.03606

1.212 1.242 1.273 1.308 1.342 1.381

0.0000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000

0.0000 0.1020 0.2028 0.3023 0.4007 0.4978 0.5937 0.6884

1.02671 1.02945 1.03213 1.03476 1.03735 1.03987 1.04234 1.04477

1.250 1.278 1.309 1.340 1.377 1.415 1.454 1.493

0.0000 0.1000 0.2001 0.3000 0.4000 0.5000 0.6000 0.7000

0.0000 0.1029 0.2046 0.3048 0.4039 0.5018 0.5984 0.6939

1.03541 1.03810 1.04074 1.04332 1.04584 1.04832 1.05073 1.05310

1.348 1.378 1.413 1.448 1.489 1.529 1.573 1.617

0.0000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000

0.0000 0.1037 0.2061 0.3073 0.4071 0.5057 0.6031 0.6992

1.04378 1.04642 1.04901 1.05154 1.05403 1.05646 1.05885 1.06119

1.443 1.478 1.517 1.559 1.603 1.649 1.697 1.749

0.0000 0.1000 0.2000 0.3000 0.4000

0.0000 0.0999 0.1980 0.2944 0.3891

1.00815 1.01077 1.01332 1.01582 1.01825

1.079 1.119 1.167 1.219 1.275

0.0000 0.1000 0.2000 0.3000 0.4000

0.0000 0.1008 0.1999 0.2971 0.3926

1.01764 1.02019 1.02268 1.02512 1.02750

1.161 1.208 1.261 1.317 1.378

0.0000 0.1000 0.2000 0.3000 0.4000

0.0000 0.1017 0.2016 0.2996 0.3960

1.02671 1.02918 1.03159 1.03394 1.03624

1.250 1.301 1.362 1.426 1.491

0.0000 0.1000 0.2000 0.3000 0.4000

0.0000 0.1026 0.2033 0.3021 0.3992

1.03541 1.03781 1.04015 1.04242 1.04463

1.348 1.415 1.503 1.614 1.732

ρ

T/K = 313.15 η

−3

g·cm

mPa·s

mb = 0.4000 mol·kg−1 1.02015 0.954 1.02280 0.976 1.02539 1.000 1.02794 1.026 1.03045 1.054 1.03293 1.082 mb = 0.6000 mol·kg−1 1.02367 0.981 1.02636 1.001 1.02900 1.024 1.03159 1.048 1.03414 1.073 1.03663 1.103 1.03908 1.134 1.04147 1.165 mb = 0.8000 mol·kg−1 1.03222 1.059 1.03487 1.081 1.03747 1.105 1.04001 1.131 1.04250 1.159 1.04495 1.190 1.04735 1.222 1.04970 1.254 mb = 1.0000 mol·kg−1 1.04041 1.128 1.04301 1.154 1.04556 1.181 1.04806 1.212 1.05052 1.242 1.05293 1.277 1.05530 1.313 1.05761 1.350 L-Valine in Xylitol Aqueous Solution mb = 0.2000 mol·kg−1 1.00542 0.855 1.00800 0.885 1.01052 0.920 1.01298 0.958 1.01539 0.997 mb = 0.4000 mol·kg−1 1.01474 0.916 1.01725 0.950 1.01970 0.989 1.02210 1.030 1.02444 1.074 mb = 0.6000 mol·kg−1 1.02367 0.981 1.02610 1.019 1.02846 1.063 1.03077 1.109 1.03302 1.157 mb = 0.8000 mol·kg−1 1.03222 1.059 1.03457 1.107 1.03687 1.171 1.03910 1.248 1.04127 1.332

C

ρ g·cm

T/K = 323.15 η

−3

ρ

η −3

mPa·s

g·cm

mPa·s

1.01641 1.01902 1.02158 1.02411 1.02660 1.02903

0.773 0.790 0.808 0.828 0.848 0.870

1.01190 1.01449 1.01705 1.01957 1.02206 1.02452

0.640 0.654 0.669 0.683 0.700 0.717

1.01985 1.02251 1.02512 1.02768 1.03021 1.03270 1.03513 1.03752

0.794 0.809 0.826 0.844 0.864 0.886 0.908 0.932

1.01535 1.01798 1.02057 1.02312 1.02563 1.02811 1.03055 1.03293

0.657 0.669 0.683 0.697 0.713 0.729 0.746 0.764

1.02828 1.03089 1.03346 1.03598 1.03845 1.04088 1.04328 1.04561

0.851 0.868 0.886 0.906 0.927 0.950 0.974 0.999

1.02370 1.02629 1.02884 1.03134 1.03381 1.03624 1.03862 1.04096

0.701 0.715 0.729 0.745 0.760 0.778 0.796 0.815

1.03638 1.03894 1.04147 1.04395 1.04639 1.04878 1.05113 1.05345

0.904 0.922 0.943 0.965 0.990 1.016 1.042 1.069

1.03165 1.03419 1.03670 1.03917 1.04160 1.04400 1.04636 1.04869

0.741 0.755 0.772 0.789 0.808 0.827 0.848 0.869

1.00185 1.00439 1.00687 1.00930 1.01168

0.697 0.720 0.747 0.775 0.805

0.99756 1.00005 1.00250 1.00489 1.00724

0.582 0.600 0.620 0.641 0.664

1.01107 1.01354 1.01596 1.01832 1.02062

0.744 0.770 0.800 0.831 0.863

1.00660 1.00902 1.01140 1.01372 1.01600

0.617 0.637 0.660 0.684 0.708

1.01985 1.02224 1.02457 1.02685 1.02908

0.794 0.823 0.856 0.890 0.924

1.01535 1.01769 1.01997 1.02221 1.02440

0.657 0.680 0.703 0.729 0.756

1.02828 1.03059 1.03284 1.03504 1.03718

0.851 0.889 0.935 0.995 1.058

1.02370 1.02596 1.02818 1.03035 1.03248

0.701 0.729 0.764 0.807 0.853



Article


ρ

C −1

mol·L

−1

T/K = 303.15 η

−3

g·cm

mPa·s

0.0000 0.1000 0.2000 0.3000 0.4000

0.0000 0.1034 0.2049 0.3045 0.4022

1.04378 1.04610 1.04836 1.05055 1.05268

1.443 1.512 1.586 1.665 1.746

0.0000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000

0.0000 0.1000 0.1986 0.2956 0.3911 0.4852 0.5779 0.6691

1.00815 1.01233 1.01643 1.02044 1.02436 1.02820 1.03195 1.03561

1.079 1.116 1.154 1.194 1.236 1.279 1.325 1.371

0.0000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000

0.0000 0.1010 0.2004 0.2983 0.3947 0.4896 0.5830 0.6750

1.01764 1.02177 1.02580 1.02976 1.03363 1.03742 1.04113 1.04477

1.161 1.203 1.247 1.292 1.339 1.388 1.439 1.491

0.0000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000

0.0000 0.1019 0.2022 0.3008 0.3980 0.4937 0.5879 0.6806

1.02671 1.03079 1.03477 1.03866 1.04247 1.04618 1.04984 1.05338

1.250 1.298 1.346 1.397 1.450 1.505 1.562 1.619

0.0000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000

0.0000 0.1027 0.2038 0.3033 0.4013 0.4977 0.5926 0.6860

1.03541 1.03942 1.04334 1.04718 1.05094 1.05462 1.05823 1.06177

1.348 1.406 1.462 1.510 1.569 1.629 1.691 1.759

0.0000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000

0.0000 0.1035 0.2054 0.3057 0.4043 0.5015 0.5970 0.6911

1.04378 1.04771 1.05157 1.05534 1.05904 1.06266 1.06621 1.06969

1.443 1.508 1.566 1.630 1.694 1.763 1.830 1.908

0.0000 0.1000 0.2000 0.3000 0.4000 0.5000

0.0000 0.0996 0.1967 0.2915 0.3840 0.4743

1.00815 1.01305 1.01780 1.02239 1.02684 1.03116

1.079 1.136 1.199 1.264 1.335 1.411

ρ

T/K = 313.15 η

−3

g·cm

mPa·s

mb = 1.0000 mol·kg−1 1.04041 1.128 1.04269 1.176 1.04491 1.228 1.04707 1.280 1.04917 1.338 L-Threonine in Xylitol Aqueous Solution mb = 0.2000 mol·kg−1 1.00542 0.855 1.00955 0.883 1.01359 0.911 1.01754 0.942 1.02140 0.972 1.02520 1.005 1.02889 1.038 1.03251 1.073 mb = 0.4000 mol·kg−1 1.01474 0.916 1.01881 0.947 1.02279 0.979 1.02669 1.012 1.03052 1.048 1.03426 1.084 1.03793 1.121 1.04153 1.159 mb = 0.6000 mol·kg−1 1.02367 0.981 1.02769 1.017 1.03161 1.052 1.03544 1.090 1.03919 1.128 1.04285 1.168 1.04645 1.210 1.04996 1.252 mb = 0.8000 mol·kg−1 1.03222 1.059 1.03617 1.099 1.04004 1.136 1.04383 1.177 1.04754 1.218 1.05118 1.262 1.05476 1.303 1.05826 1.347 mb = 1.0000 mol·kg−1 1.04041 1.128 1.04429 1.171 1.04810 1.215 1.05184 1.262 1.05551 1.307 1.05911 1.357 1.06264 1.405 1.06612 1.458 L-Arginine in Xylitol Aqueous Solution mb = 0.2000 mol·kg−1 1.00542 0.855 1.01025 0.898 1.01492 0.946 1.01944 0.994 1.02382 1.048 1.02808 1.104 D

ρ g·cm

T/K = 323.15 η

−3

ρ

η −3

mPa·s

g·cm

mPa·s

1.03638 1.03862 1.04080 1.04293 1.04499

0.904 0.940 0.980 1.020 1.060

1.03165 1.03385 1.03600 1.03810 1.04016

0.741 0.769 0.798 0.828 0.859

1.00185 1.00593 1.00992 1.01384 1.01767 1.02143 1.02509 1.02868

0.697 0.719 0.741 0.764 0.787 0.812 0.838 0.864

0.99756 1.00160 1.00555 1.00944 1.01325 1.01697 1.02063 1.02422

0.582 0.598 0.615 0.634 0.652 0.672 0.691 0.713

1.01107 1.01508 1.01902 1.02288 1.02667 1.03040 1.03404 1.03763

0.744 0.768 0.792 0.818 0.844 0.872 0.900 0.926

1.00660 1.01057 1.01447 1.01830 1.02206 1.02577 1.02941 1.03298

0.617 0.636 0.650 0.675 0.696 0.718 0.739 0.762

1.01985 1.02382 1.02770 1.03150 1.03522 1.03886 1.04242 1.04590

0.794 0.820 0.848 0.878 0.906 0.936 0.966 0.998

1.01535 1.01927 1.02312 1.02689 1.03059 1.03422 1.03777 1.04125

0.657 0.677 0.698 0.720 0.743 0.766 0.791 0.815

1.02828 1.03218 1.03600 1.03976 1.04343 1.04705 1.05060 1.05409

0.851 0.882 0.911 0.943 0.972 1.005 1.037 1.073

1.02370 1.02756 1.03134 1.03507 1.03872 1.04231 1.04585 1.04931

0.701 0.723 0.747 0.771 0.794 0.819 0.844 0.872

1.03638 1.04022 1.04398 1.04768 1.05131 1.05488 1.05839 1.06184

0.904 0.935 0.969 1.004 1.038 1.072 1.109 1.145

1.03165 1.03544 1.03917 1.04284 1.04644 1.04999 1.05347 1.05690

0.741 0.765 0.790 0.818 0.844 0.871 0.899 0.929

1.00185 1.00661 1.01123 1.01570 1.02004 1.02427

0.697 0.731 0.767 0.805 0.846 0.890

0.99756 1.00226 1.00682 1.01125 1.01556 1.01977

0.582 0.608 0.637 0.667 0.699 0.734



Article


ρ

C −1

mol·L

−1

T/K = 303.15 η

−3

g·cm

mPa·s

0.6000 0.7000

0.5624 0.6484

1.03534 1.03936

1.490 1.575

0.0000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000

0.0000 0.1005 0.1985 0.2941 0.3874 0.4783 0.5672 0.6539

1.01764 1.02243 1.02706 1.03154 1.03587 1.04006 1.04414 1.04808

1.161 1.226 1.294 1.369 1.448 1.533 1.623 1.718

0.0000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000

0.0000 0.1014 0.2002 0.2966 0.3906 0.4823 0.5718 0.6592

1.02671 1.03141 1.03595 1.04034 1.04459 1.04870 1.05267 1.05653

1.250 1.323 1.400 1.484 1.573 1.668 1.767 1.875

0.0000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000

0.0000 0.1022 0.2019 0.2990 0.3937 0.4861 0.5763 0.6642

1.03541 1.04002 1.04446 1.04876 1.05291 1.05692 1.06079 1.06455

1.348 1.432 1.517 1.607 1.706 1.813 1.925 2.046

0.0000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000

0.0000 0.1030 0.2034 0.3013 0.3967 0.4898 0.5805 0.6690

1.04378 1.04829 1.05264 1.05685 1.06091 1.06484 1.06863 1.07232

1.443 1.533 1.633 1.737 1.851 1.965 2.091 2.230

ρ

T/K = 313.15 η

−3

g·cm

mPa·s

mb = 0.2000 1.03219 1.03617 mb = 0.4000 1.01474 1.01945 1.02400 1.02841 1.03269 1.03682 1.04083 1.04472 mb = 0.6000 1.02367 1.02828 1.03274 1.03706 1.04125 1.04532 1.04923 1.05304 mb = 0.8000 1.03222 1.03674 1.04112 1.04536 1.04945 1.05340 1.05723 1.06096 mb = 1.0000 1.04041 1.04484 1.04913 1.05329 1.05730 1.06118 1.06493 1.06860

mol·kg−1 1.163 1.226 mol·kg−1 0.916 0.964 1.016 1.071 1.130 1.192 1.258 1.328 mol·kg−1 0.981 1.036 1.093 1.154 1.221 1.290 1.362 1.442 mol·kg−1 1.059 1.118 1.182 1.250 1.322 1.399 1.475 1.561 mol·kg−1 1.128 1.195 1.264 1.342 1.420 1.503 1.593 1.690

ρ g·cm

T/K = 323.15 η

−3

ρ

η −3

mPa·s

g·cm

mPa·s

1.02835 1.03230

0.934 0.982

1.02383 1.02779

0.769 0.806

1.01107 1.01572 1.02022 1.02459 1.02881 1.03290 1.03690 1.04075

0.744 0.782 0.821 0.864 0.908 0.956 1.006 1.059

1.00660 1.01120 1.01567 1.02000 1.02422 1.02832 1.03230 1.03615

0.617 0.647 0.679 0.712 0.747 0.785 0.824 0.865

1.01985 1.02440 1.02882 1.03310 1.03726 1.04130 1.04518 1.04896

0.794 0.834 0.879 0.926 0.978 1.029 1.083 1.143

1.01535 1.01986 1.02423 1.02848 1.03260 1.03660 1.04048 1.04427

0.657 0.689 0.724 0.761 0.801 0.840 0.883 0.929

1.02828 1.03275 1.03707 1.04127 1.04533 1.04926 1.05307 1.05680

0.851 0.895 0.946 0.996 1.050 1.108 1.168 1.231

1.02370 1.02812 1.03241 1.03658 1.04061 1.04453 1.04833 1.05205

0.701 0.737 0.776 0.816 0.857 0.900 0.947 0.997

1.03638 1.04076 1.04500 1.04911 1.05308 1.05694 1.06068 1.06432

0.904 0.953 1.006 1.065 1.124 1.187 1.254 1.324

1.03165 1.03598 1.04019 1.04428 1.04824 1.05211 1.05583 1.05948

0.741 0.780 0.822 0.866 0.913 0.961 1.013 1.067

a ma stands for the molality of glycine/L-alanine/L-threonine/L-valine/L-arginine in the (xylitol + water) mixture solvents. mb stands for the molality of xylitol in pure water. C stands for the molar concentration of amino acid in the xylitol aqueous solution at 293.15 K. ur(m) = 0.01, ur(C) = 0.01, u(ρ) = 1 × 10−4 g·cm−3, u(T) = 0.03 K for density; ur(η) = 0.005, u(T) = 0.05 K for viscosity; u(p) = 0.5 kPa.

In this paper, as a continuation of our previous researches,10,11 the densities and viscosities of glycine, L-alanine, L-valine, L-threonine, and L-arginine in aqueous xylitol solutions of (0.2, 0.4, 0.6, 0.8, 1.0) mol·kg−1 were measured at T = (293.15, 303.15, 313.15, 323.15) K, and the apparent molar volume (Vφ), transfer partial molar volume (ΔtrVφ0), interaction coefficient, viscosity B-coefficient, the free energies of activation per mole of solvent (Δμ10≠) and solute (Δμ20≠) and the hydration number were further calculated from these experimental data.

balance (FA2204B, Shanghai Jingke, China), and the uncertainty for the balance is 0.0001 g. 2.2. Density and Viscosity Measurements. The measurement of density for the experimental solution was carried out by a vibrating tube densimeter (Anton Paar DMA 4500 M, Austria) with a precision in density value of ±5 × 10−5 g·cm−3, and the temperature was controlled automatically with a precision of ±0.03 K. Before each measurement, the apparatus was calibrated using the deionized water and dry air. Each sample was measured for three times to obtain the average value of density, and after each measurement the distilled-water and anhydrous ethanol were used to clean the vibrating tube automatically. The densities of the amino acids in xylitol aqueous solutions are listed in Table 2. The viscosities of amino acids in xylitol aqueous solutions were determined by means of an iVisc capillary viscometer (LAUDA, Germany), and the Ubbelohde capillary (1834A) with 0.53 mm

2. EXPERIMENTAL SECTION 2.1. Chemicals. Xylitol, glycine, L -alanine, L -valine, and L-arginine are analytical grade reagents; more details are listed in Table 1. All measured solutions were prepared with distilled water at room temperature using an electronic L-threonine,

E



Article

Figure 1. Comparisons of the densities and viscosities of xylitol aqueous solutions between the experimental data and literature values. (a), density; (b), viscosity. ⬠, 288.15 K; □, 293.15 K; ◇, 298.15 K; ○, 303.15 K; ◁, 308.15 K; △, 313.15 K; ▷, 318.15 K; ▽, 323.15 K; solid symbols for experimental data; hollow symbols for literature values in ref 13; cross-filled symbols for literature values in ref 14; vertical line-filled symbols for literature values in ref 15; horizontal line-filled symbols for literature values in ref 16; ---, fitted curve of experimental data.

Figure 2. Comparisons of the densities of glycine, L-alanine, L-valine in xylitol aqueous solutions between the experimental data and literature values. (a), glycine, ma = 0.2 mol·kg−1; (b) L-alanine, ma = 0.2 mol·kg−1; (c), L-valine, ma = 0.1 mol·kg−1. This work: ■, 293.15 K; ●, 303.15 K; ▲, 313.15 K; ▼, 323.15 K; ref 17: ◇, 298.15 K; ---, fitted curve of experimental data.

mb = (0.2, 0.4, 0.6, 0.8, 1.0) mol·kg−1 aqueous xylitol solutions at T = (293.15, 303.15, 313.15, 323.15) K are given in Table 2. The comparisons of densities and viscosities for five amino acids with literature data could be found in our previous paper,10 it showed a good agreement. The comparisons of the densities and viscosities for binary solutions (xylitol + water) with literature values13−16 are shown in Figure 1. The density shows a good linear relationship to the molality of xylitol, and the deviation between the fitted curves by experiment data and literature values13 is within ±0.1%, indicating an excellent agreement. The experimental viscosities are slightly lower than those in the literature13 except for T = 293.15 K; the maximum deviation between the fitted curves by the experimental viscosities and literature values13 is 4.6%, and the average deviation is 2.1%. The densities and viscosities between the literature14−16 and this work are different due to different measurement temperatures and concentrations as shown in Figure 1. It is worthy noting that the densities at 288.15 K in the literature15 are very closed to the fitted curve by the present experimental data at 293.15 K; the large discrepancy could be attributed to the differences of impurities and the measure instrument, etc. Furthermore, Xu17 presented the densities of glycine, L-alanine, and L-valine in xylitol

diameter was supplied by Shanghai Glass Instruments Factory of China. The perfectly cleaned and dried Ubbelohde capillary with experimental solution was vertically placed in a Lauda Eco Sliver thermostat with a precision ±0.05 K. The flow time for each sample was detected by the infrared automatically with a precision of ±0.01 s. An average of at least four sets of flow time with a deviation of 0.2 s was taken for each sample at the required temperature. Since all flow times were greater than 100 s, the kinetic energy and the end corrections were found to be negligible. The viscosities of amino acids in xylitol aqueous solutions were computed by the following equation:12 η /η0 = ρt /ρ0 t0

(1)

where η, ρ, t and η0, ρ0, t0 are viscosities, densities, and flow times of the measured solution and viscosity standard solution, respectively. The viscosities of the measured solutions are included in Table 2.

3. RESULTS AND DISCUSSION 3.1. Volumetric Properties. The experimental densities for glycine, L-alanine, L-valine, L-threonine, and L-arginine at F



Article

Table 3. Apparent Molar Volumes of Amino Acids in Xylitol Aqueous Solutions

Table 3. continued Vφ/ cm3·mol−1

Vφ/ cm3·mol−1 ma/ mol·kg−1

0.1001 0.2000 0.3000 0.4000 0.5000 0.6001 0.7000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000 0.1001 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000

0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000

C/ mol·L−1

T/K = 293.15

T/K = 303.15

T/K = 313.15

Glycine in Xylitol Aqueous Solution mb = 0.2000 mol·kg−1 0.1004 43.06 43.52 43.96 0.1999 43.17 43.63 44.08 0.2986 43.29 43.76 44.19 0.3963 43.41 43.88 44.31 0.4933 43.54 44.00 44.43 0.5894 43.67 44.14 44.53 0.6845 43.80 44.25 44.67 mb = 0.4000 mol·kg−1 0.1013 43.45 43.98 44.42 0.2018 43.54 44.05 44.48 0.3013 43.61 44.12 44.53 0.4000 43.69 44.18 44.58 0.4978 43.76 44.26 44.64 0.5947 43.84 44.33 44.68 0.6907 43.91 44.40 44.74 mb = 0.6000 mol·kg−1 0.1022 43.56 44.11 44.55 0.2035 43.66 44.19 44.64 0.3040 43.76 44.30 44.72 0.4034 43.87 44.41 44.80 0.5020 43.98 44.49 44.89 0.5998 44.08 44.61 44.97 0.6965 44.20 44.72 45.06 mb = 0.8000 mol·kg−1 0.1032 43.73 44.21 44.68 0.2053 43.85 44.32 44.76 0.3065 43.98 44.42 44.84 0.4067 44.10 44.52 44.91 0.5061 44.22 44.63 45.00 0.6046 44.35 44.74 45.10 0.7021 44.46 44.85 45.19 mb = 1.0000 mol·kg−1 0.1039 43.93 44.35 44.76 0.2069 44.04 44.45 44.84 0.3088 44.15 44.55 44.93 0.4099 44.26 44.65 45.01 0.5101 44.38 44.76 45.11 0.6093 44.50 44.87 45.20 0.7076 44.62 44.98 45.29 L-Alanine in Xylitol Aqueous Solution mb = 0.2000 mol·kg−1 0.1002 60.32 60.81 61.26 0.1992 60.42 60.89 61.32 0.2970 60.52 60.98 61.40 0.3936 60.61 61.08 61.48 0.4891 60.71 61.17 61.56 0.5834 60.78 61.26 61.63 0.6766 60.87 61.34 61.67 mb = 0.4000 mol·kg−1 0.1011 60.57 61.12 61.64 0.2010 60.66 61.18 61.67 0.2997 60.73 61.23 61.72 0.3972 60.82 61.30 61.77 0.4935 60.87 61.36 61.81 0.5887 60.97 61.41 61.84

T/K = 323.15

ma/ mol·kg−1

C/ mol·L−1

0.7000

0.6827

44.39 44.50 44.59 44.70 44.80 44.88 44.97

0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000

44.81 44.84 44.87 44.89 44.92 44.94 44.96

0.1000 0.2001 0.3000 0.4000 0.5000 0.6000 0.7000

44.91 44.97 45.03 45.09 45.17 45.24 45.29

0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000

45.01 45.09 45.14 45.20 45.27 45.33 45.39

0.1000 0.2000 0.3000 0.4000 0.1000 0.2000 0.3000 0.4000

45.15 45.21 45.26 45.32 45.39 45.46 45.52

0.1000 0.2000 0.3000 0.4000 0.1000 0.2000 0.3000 0.4000

61.77 61.82 61.88 61.90 61.96 61.99 62.03

0.1000 0.2000 0.3000 0.4000

62.02 62.04 62.06 62.09 62.10 62.12

0.1000 0.2000 0.3000 0.4000

G

T/K = 293.15

T/K = 303.15

T/K = 313.15

mb = 0.4000 mol·kg−1 61.03 61.45 61.92 mb = 0.6000 mol·kg−1 0.1020 60.62 61.17 61.65 0.2028 60.73 61.28 61.72 0.3023 60.83 61.35 61.78 0.4007 60.92 61.43 61.83 0.4978 61.02 61.52 61.87 0.5937 61.13 61.60 61.94 0.6884 61.22 61.69 62.01 mb = 0.8000 mol·kg−1 0.1029 60.76 61.28 61.77 0.2046 60.88 61.39 61.83 0.3048 60.99 61.48 61.90 0.4039 61.11 61.57 61.98 0.5018 61.20 61.65 62.04 0.5984 61.32 61.74 62.09 0.6939 61.42 61.83 62.17 mb = 1.0000 mol·kg−1 0.1037 60.97 61.46 61.94 0.2061 61.06 61.54 61.98 0.3073 61.15 61.61 62.02 0.4071 61.23 61.68 62.07 0.5057 61.32 61.75 62.14 0.6031 61.41 61.82 62.18 0.6992 61.50 61.91 62.24 L-Valine in Xylitol Aqueous Solution mb = 0.2000 mol·kg−1 0.0999 90.20 90.77 91.40 0.1980 90.29 90.83 91.45 0.2944 90.37 90.91 91.50 0.3891 90.45 90.96 91.54 mb = 0.4000 mol·kg−1 0.1008 90.25 90.85 91.48 0.1999 90.32 90.92 91.53 0.2971 90.37 90.98 91.58 0.3926 90.44 91.03 91.65 mb = 0.6000 mol·kg−1 0.1017 90.43 91.07 91.71 0.2016 90.51 91.15 91.76 0.2996 90.59 91.22 91.80 0.3960 90.67 91.30 91.85 mb = 0.8000 mol·kg−1 0.1026 90.55 91.20 91.88 0.2033 90.64 91.26 91.94 0.3021 90.73 91.36 92.01 0.3992 90.83 91.45 92.09 mb = 1.0000 mol·kg−1 0.1034 90.74 91.34 91.99 0.2049 90.83 91.42 92.07 0.3045 90.93 91.52 92.14 0.4022 91.04 91.60 92.22 L-Threonine in Xylitol Aqueous Solution mb = 0.2000 mol·kg−1 0.1000 76.68 77.33 77.96 0.1986 76.82 77.46 78.07 0.2956 76.93 77.59 78.15 0.3911 77.05 77.72 78.27

T/K = 323.15 62.13 62.07 62.11 62.13 62.18 62.21 62.24 62.30 62.19 62.20 62.26 62.30 62.34 62.39 62.44 62.31 62.33 62.36 62.38 62.40 62.43 62.45

92.16 92.18 92.19 92.21 92.24 92.28 92.31 92.33 92.51 92.54 92.57 92.60 92.64 92.66 92.68 92.70 92.72 92.75 92.78 92.80

78.55 78.65 78.70 78.78



Article

Table 3. continued

Table 3. continued Vφ/ cm3·mol−1

ma/ mol·kg−1

C/ mol·L−1

0.5000 0.6000 0.7000

0.4852 0.5779 0.6691

0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000

0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000 0.1000 0.2000 0.3000 0.4000

T/K = 293.15

T/K = 303.15

T/K = 313.15

mb = 0.2000 mol·kg−1 77.18 77.82 78.36 77.31 77.97 78.50 77.46 78.10 78.61 mb = 0.4000 mol·kg−1 0.1010 76.91 77.60 78.26 0.2004 77.05 77.70 78.34 0.2983 77.15 77.79 78.41 0.3947 77.24 77.88 78.47 0.4896 77.36 77.99 78.51 0.5830 77.48 78.08 78.58 0.6750 77.58 78.17 78.64 mb = 0.6000 mol·kg−1 0.1019 77.03 77.72 78.35 0.2022 77.20 77.89 78.47 0.3008 77.34 78.02 78.57 0.3980 77.47 78.16 78.68 0.4937 77.61 78.29 78.79 0.5879 77.71 78.40 78.90 0.6806 77.87 78.52 79.01 mb = 0.8000 mol·kg−1 0.1027 77.39 78.05 78.68 0.2038 77.50 78.14 78.74 0.3033 77.59 78.22 78.79 0.4013 77.69 78.31 78.87 0.4977 77.78 78.38 78.92 0.5926 77.86 78.44 78.96 0.6860 77.95 78.52 79.00 mb = 1.0000 mol·kg−1 0.1035 77.74 78.34 78.94 0.2054 77.82 78.39 78.99 0.3057 77.89 78.44 79.02 0.4043 77.98 78.48 79.05 0.5015 78.06 78.55 79.08 0.5970 78.14 78.59 79.12 0.6911 78.22 78.63 79.14 L-Arginine in Xylitol Aqueous Solution mb = 0.2000 mol·kg−1 0.0996 123.94 124.91 125.82 0.1967 124.14 125.09 125.98 0.2915 124.32 125.27 126.12 0.3840 124.50 125.45 126.28 0.4743 124.67 125.61 126.38 0.5624 124.84 125.78 126.53 0.6484 125.05 125.95 126.69 mb = 0.4000 mol·kg−1 0.1005 124.37 125.34 126.26 0.1985 124.56 125.54 126.39 0.2941 124.74 125.72 126.52 0.3874 124.93 125.86 126.69 0.4783 125.12 126.04 126.84 0.5672 125.27 126.19 126.94 0.6539 125.43 126.34 127.08 mb = 0.6000 mol·kg−1 0.1014 124.52 125.59 126.47 0.2002 124.73 125.76 126.57 0.2966 124.92 125.92 126.69 0.3906 125.08 126.06 126.80

Vφ/ cm3·mol−1 T/K = 323.15

ma/ mol·kg−1

C/ mol·L−1

78.89 78.96 79.04

0.5000 0.6000 0.7000

0.4823 0.5718 0.6592

78.86 78.92 78.95 78.99 79.01 79.04 79.08

0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000

0.1022 0.2019 0.2990 0.3937 0.4861 0.5763 0.6642

78.98 79.06 79.13 79.18 79.25 79.34 79.42

0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000

0.1030 0.2034 0.3013 0.3967 0.4898 0.5805 0.6690

T/K = 293.15

T/K = 303.15

mb = 0.6000 mol·kg−1 125.26 126.18 125.45 126.36 125.61 126.51 mb = 0.8000 mol·kg−1 124.71 125.75 124.94 125.89 125.12 126.06 125.32 126.23 125.51 126.41 125.71 126.57 125.87 126.70 mb = 1.0000 mol·kg−1 124.98 125.94 125.15 126.08 125.34 126.21 125.51 126.37 125.70 126.53 125.88 126.69 126.02 126.79

T/K = 313.15

T/K = 323.15

126.89 127.06 127.19

127.67 127.78 127.84

126.61 126.74 126.86 126.98 127.13 127.27 127.34

127.44 127.52 127.60 127.72 127.81 127.92 127.98

126.80 126.90 127.03 127.16 127.28 127.39 127.49

127.60 127.68 127.74 127.83 127.88 127.98 128.05

aqueous solutions at 298.15 K. In Figure 2, we could easily observe that the trend of literature values17 is consistent with the experimental data, and the density values at 298.15 K are in between the measured values at 293.15 and 303.15 K. The maximum deviation between the fitted curves by experimental densities and literature values17 is 4.7%, and the average deviation is 1.7%. This shows our experimental values are in line with the literature. 3.1.1. Apparent Molar Volumes. The apparent molar volume is an important volumetric property, it could be calculated by the following equation:18,19 ρ − ρ0 M − Vφ = ρ mρρ0 (2)

79.28 79.31 79.34 79.38 79.42 79.43 79.47 79.54 79.55 79.57 79.59 79.60 79.62 79.63

where Vφ (m3·mol−1) is the apparent molar volume, M (kg·mol−1) and m (mol·kg−1) are the molar mass and the molality of amino acid, respectively. ρ0 (kg·m−3) and ρ (kg·m−3) are the densities of the solvent and the solution, respectively. The values of apparent molar volume (Vφ) are listed in Table 3. It is noteworthy that the apparent molar volume increases with the rise of the solute and xylitol concentration, as well as the temperature. For the five amino acids, the apparent molar volume increases in the order: glycine < L-alanine < L-threonine < L-valine < L-arginine. The relationship between apparent molar volume and solute concentration could be expressed as follows:20,21

126.83 126.93 127.01 127.11 127.16 127.28 127.37

Vφ = V φ0 + Svma

127.08 127.17 127.27 127.35 127.44 127.53 127.65

(3)

Vφ0

where is the limiting partial molar volume and obtained by the least-squares method, Sv is the fitting slope parameter, representing solute−solute interaction.21 Sv of five amino acids in different concentrations of xylitol solution are positive, indicating stronger solute−solute interactions. Sv is affected by many factors,21 and does not present the certain regularity. The limiting partial molar volume, Vφ0 reflects solute−solvent interaction.22 It could be found from Table 4 that Vφ0 values are positive and increase with temperature. For the five amino acids, the order of Vφ0 is glycine < L-alanine < L-threonine < L-valine < 9,23 L-arginine, and same results were also obtained in the literature.

127.26 127.36 127.46 127.57

H


−1

60.17 60.24 60.50 60.52 60.66 60.88

90.07 90.12 90.19 90.35 90.46 90.64

76.54 76.55 76.82 76.92 77.31 77.66

123.73 123.77 124.21 124.36 124.54 124.81

0.0000 0.2000 0.4000 0.6000 0.8000 1.0000

0.0000 0.2000 0.4000 0.6000 0.8000 1.0000

0.0000 0.2000 0.4000 0.6000 0.8000 1.0000

0.0000 0.2000 0.4000 0.6000 0.8000 1.0000

cm ·mol

3

42.71 42.92 43.38 43.45 43.61 43.81

−1

0.0000 0.2000 0.4000 0.6000 0.8000 1.0000

mol·kg

mb

Vφ0

I

0.04 0.48 0.63 0.81 1.08

0.02 0.28 0.38 0.77 1.12

0.05 0.14 0.28 0.39 0.57

0.07 0.33 0.35 0.49 0.71

0.21 0.67 0.73 0.90 1.10

−1

cm ·mol

3

ΔtrVφ0

T/K = 293.15 Sv −2

1.8129 1.7795 1.8002 1.9216 1.7603

1.2750 1.0933 1.3599 0.9297 0.8023

0.8509 0.6200 0.8046 0.9195 0.9767

0.9086 0.7671 0.9994 1.0914 0.8897

1.2434 0.7554 1.0666 1.2202 1.1541

cm ·kg·mol 3

−1

124.66 124.75 125.20 125.45 125.58 125.79

77.16 77.20 77.50 77.62 77.98 78.29

90.63 90.71 90.80 91.00 91.11 91.25

60.58 60.72 61.07 61.10 61.20 61.39

43.31 43.39 43.90 43.99 44.11 44.24

cm ·mol 3

Vφ0

0.09 0.54 0.79 0.92 1.13

0.04 0.34 0.46 0.82 1.13

0.08 0.17 0.37 0.48 0.62

0.14 0.49 0.52 0.62 0.81

0.08 0.59 0.68 0.79 0.93

cm ·mol 3

−1

ΔtrVφ0

T/K = 303.15 Sv −2

1.7245 1.6470 1.5060 1.6248 1.4646

1.2714 0.9575 1.3128 0.7754 0.5025 L-Arginine

0.6438 0.5883 0.7633 0.8374 0.8639 L-Threonine

0.8963 0.5676 0.8439 0.8973 0.7392 L-Valine

1.2324 0.7102 1.0275 1.0560 1.0377 L-Alanine

Glycine

cm ·kg·mol 3

−1

125.50 125.69 126.12 126.33 126.49 126.68

77.78 77.84 78.21 78.25 78.63 78.92

91.24 91.36 91.42 91.67 91.81 91.91

61.04 61.19 61.58 61.60 61.70 61.88

43.82 43.84 44.37 44.47 44.59 44.66

cm ·mol 3

Vφ0

0.19 0.62 0.83 0.99 1.18

0.06 0.43 0.47 0.85 1.14

0.12 0.18 0.43 0.57 0.67

0.15 0.54 0.56 0.66 0.84

0.03 0.55 0.65 0.77 0.85

−1

cm ·mol 3

ΔtrVφ 0

T/K = 313.15 Sv

1.4137 1.3920 1.1908 1.2530 1.1755

1.0786 0.6159 1.0903 0.5511 0.3293

0.4700 0.5459 0.4687 0.6974 0.7725

0.7150 0.4561 0.5678 0.6705 0.5045

1.1680 0.5331 0.8408 0.8478 0.8933

cm ·kg·mol 3

−2

−1

126.29 126.75 126.98 127.17 127.34 127.52

78.38 78.47 78.84 78.91 79.25 79.53

92.01 92.14 92.22 92.47 92.62 92.70

61.43 61.74 62.01 62.03 62.13 62.28

44.29 44.30 44.79 44.84 44.95 45.08

cm ·mol 3

Vφ0

0.46 0.69 0.88 1.05 1.23

0.09 0.46 0.53 0.87 1.15

0.13 0.21 0.46 0.61 0.69

0.31 0.58 0.60 0.70 0.85

0.02 0.50 0.55 0.67 0.79

cm3·mol−1

ΔtrVφ0

T/K = 323.15

0.8777 0.9258 0.9900 0.9388 0.7448

0.8143 0.3389 0.7106 0.3211 0.1500

0.1902 0.3034 0.3187 0.1982 0.2610

0.4281 0.1865 0.3750 0.4321 0.2412

0.9738 0.2489 0.6540 0.6277 0.6252

cm3·kg·mol−2

Sv

Table 4. Limiting Partial Molar Volumes (Vφ0), Limiting Partial Molar Volumes of Transfer (ΔtrVφ0) and the Experimental Slope (Sv) of Amino Acids in Xylitol Aqueous Solutions at T = (293.15 to 323.15) K

Journal of Chemical & Engineering Data Article



Article

Table 5. Viscosity Coefficients for Amino Acids in Xylitol Aqueous Solutions T/(K)

B/(dm3·mol−1)

293.15 303.15 313.15 323.15

0.093 0.095 0.101 0.107

± ± ± ±

293.15 303.15 313.15 323.15

0.098 0.106 0.109 0.111

± ± ± ±

293.15 303.15 313.15 323.15

0.107 0.114 0.120 0.123

± ± ± ±

293.15 303.15 313.15 323.15

0.113 0.120 0.129 0.134

± ± ± ±

293.15 303.15 313.15 323.15

0.126 0.134 0.141 0.148

± ± ± ±

± ± ± ±

mb 0.004 0.001 0.003 0.003 mb 0.002 0.001 0.001 0.002 mb 0.003 0.003 0.002 0.002 mb 0.002 0.002 0.001 0.002 mb 0.002 0.002 0.001 0.002

± ± ± ±

mb 0.004 0.008 0.004 0.002

293.15 303.15 313.15 323.15

0.185 0.179 0.167 0.152

± ± ± ±

293.15 303.15 313.15 323.15

0.195 0.183 0.173 0.169

± ± ± ±

293.15 303.15 313.15 323.15

0.209 0.188 0.177 0.174

± ± ± ±

293.15 303.15 313.15 323.15

0.213 0.191 0.181 0.178

± ± ± ±

293.15 303.15 313.15 323.15

293.15 303.15 313.15 323.15

0.228 0.207 0.190 0.183

0.352 0.334 0.322 0.287

mb 0.001 0.002 0.001 0.001 mb 0.001 0.001 0.001 0.001 mb 0.001 0.001 0.001 0.001 mb 0.001 0.002 0.000 0.001 mb 0.002 0.003 0.001 0.001

D/(dm6·mol−2) Glycine = 0.2000 mol·kg−1 0.053 ± 0.002 0.055 ± 0.003 0.051 ± 0.002 0.042 ± 0.002 = 0.4000 mol·kg−1 0.047 ± 0.001 0.042 ± 0.002 0.042 ± 0.002 0.042 ± 0.002 = 0.6000 mol·kg−1 0.042 ± 0.001 0.035 ± 0.002 0.030 ± 0.002 0.028 ± 0.002 = 0.8000 mol·kg−1 0.028 ± 0.001 0.023 ± 0.003 0.015 ± 0.001 0.012 ± 0.002 = 1.0000 mol·kg−1 0.043 ± 0.004 0.039 ± 0.004 0.029 ± 0.002 0.022 ± 0.002 L-Alanine = 0.2000 mol·kg−1 0.122 ± 0.007 0.115 ± 0.002 0.111 ± 0.005 0.108 ± 0.005 = 0.4000 mol·kg−1 0.120 ± 0.004 0.121 ± 0.003 0.110 ± 0.002 0.100 ± 0.003 = 0.6000 mol·kg−1 0.107 ± 0.004 0.124 ± 0.005 0.109 ± 0.003 0.091 ± 0.004 = 0.8000 mol·kg−1 0.107 ± 0.003 0.108 ± 0.004 0.099 ± 0.002 0.081 ± 0.003 = 1.0000 mol·kg−1 0.107 ± 0.003 0.106 ± 0.004 0.104 ± 0.002 0.093 ± 0.003 L-Valine = 0.2000 mol·kg−1 0.296 ± 0.011 0.240 ± 0.024 0.197 ± 0.013 0.188 ± 0.007

100AD

0.0022 0.0025 0.0018 0.0016

0.19 0.19 0.14 0.10

0.0030 0.0031 0.0024 0.0012

0.23 0.19 0.18 0.15

0.0035 0.0029 0.0028 0.0023

0.25 0.21 0.32 0.32

0.0038 0.0032 0.0048 0.0048 0.0042 0.0043 0.0035 0.0041

0.23 0.21 0.08 0.20

0.0050 0.0045 0.0016 0.0042

0.15 0.05 0.14 0.12

0.0035 0.0012 0.0031 0.0030

0.10 0.04 0.08 0.09

0.0025 0.0007 0.0021 0.0019

0.08 0.07 0.07 0.07

0.0017 0.0014 0.0013 0.0012

0.11 0.11 0.12 0.11

0.18 0.17 0.16 0.14

T/(K)

B/(dm3·mol−1)

SD/mPa·s

0.14 0.14 0.11 0.10

0.27 0.33 0.23 0.27

Table 5. continued

0.0020 0.0019 0.0020 0.0017

0.0051 0.0047 0.0042 0.0038

J

293.15 303.15 313.15 323.15

0.383 0.352 0.336 0.317

± ± ± ±

293.15 303.15 313.15 323.15

0.393 0.373 0.352 0.324

± ± ± ±

293.15 303.15 313.15 323.15

0.418 0.388 0.373 0.340

± ± ± ±

293.15 303.15 313.15 323.15

0.446 0.396 0.386 0.355

± ± ± ±

293.15 303.15 313.15 323.15

0.328 0.311 0.299 0.269

± ± ± ±

293.15 303.15 313.15 323.15

0.343 0.322 0.310 0.278

± ± ± ±

293.15 303.15 313.15 323.15

0.358 0.341 0.325 0.293

± ± ± ±

293.15 303.15 313.15 323.15

0.373 0.347 0.331 0.301

± ± ± ±

293.15 303.15 313.15 323.15

0.391 0.354 0.337 0.310

± ± ± ±

293.15 303.15 313.15 323.15

0.491 0.472 0.454 0.426

± ± ± ±

293.15 303.15 313.15 323.15

0.527 0.507 0.482 0.462

± ± ± ±

293.15 303.15

0.541 ± 0.514 ±

mb 0.004 0.005 0.005 0.005 mb 0.010 0.006 0.007 0.004 mb 0.014 0.009 0.013 0.007 mb 0.004 0.005 0.004 0.002 mb 0.001 0.002 0.002 0.003 mb 0.001 0.001 0.003 0.011 mb 0.002 0.002 0.003 0.001 mb 0.010 0.003 0.005 0.004 mb 0.007 0.003 0.005 0.003 mb 0.003 0.003 0.002 0.002 mb 0.005 0.005 0.006 0.004 mb 0.005 0.006

D/(dm6·mol−2) = 0.4000 mol·kg−1 0.235 ± 0.011 0.223 ± 0.015 0.183 ± 0.014 0.150 ± 0.016 = 0.6000 mol·kg−1 0.243 ± 0.029 0.203 ± 0.019 0.162 ± 0.022 0.142 ± 0.011 = 0.8000 mol·kg−1 0.749 ± 0.041 0.654 ± 0.027 0.593 ± 0.039 0.508 ± 0.020 = 1.0000 mol·kg−1 0.190 ± 0.010 0.166 ± 0.014 0.107 ± 0.013 0.104 ± 0.005 L-Threonine = 0.2000 mol·kg−1 0.114 ± 0.002 0.103 ± 0.004 0.088 ± 0.003 0.099 ± 0.005 = 0.4000 mol·kg−1 0.116 ± 0.002 0.105 ± 0.002 0.079 ± 0.006 0.106 ± 0.019 = 0.6000 mol·kg−1 0.111 ± 0.003 0.095 ± 0.004 0.076 ± 0.005 0.090 ± 0.002 = 0.8000 mol·kg−1 0.100 ± 0.018 0.071 ± 0.005 0.067 ± 0.009 0.076 ± 0.008 = 1.0000 mol·kg−1 0.104 ± 0.013 0.099 ± 0.006 0.071 ± 0.005 0.082 ± 0.005 L-Arginine = 0.2000 mol·kg−1 0.334 ± 0.006 0.300 ± 0.005 0.272 ± 0.004 0.258 ± 0.003 = 0.4000 mol·kg−1 0.338 ± 0.008 0.310 ± 0.009 0.302 ± 0.012 0.260 ± 0.006 = 0.6000 mol·kg−1 0.367 ± 0.010 0.324 ± 0.010

100AD

SD/mPa·s

0.11 0.11 0.10 0.09

0.0032 0.0031 0.0028 0.0026

0.11 0.08 0.08 0.06

0.0025 0.0020 0.0020 0.0015

0.14 0.12 0.12 0.10

0.0035 0.0029 0.0031 0.0023

0.14 0.13 0.11 0.11

0.0030 0.0026 0.0025 0.0022

0.39 0.37 0.35 0.33

0.0088 0.0083 0.0076 0.0074

0.30 0.29 0.26 0.33

0.0071 0.0066 0.0061 0.0069

0.23 0.22 0.20 0.18

0.0054 0.0050 0.0046 0.0044

0.27 0.15 0.20 0.17

0.0048 0.0034 0.0035 0.0032

0.20 0.17 0.13 0.13

0.0036 0.0029 0.0026 0.0025

1.13 1.07 1.02 0.97

0.0285 0.0266 0.0249 0.0235

1.00 0.94 0.89 0.86

0.0259 0.0240 0.0224 0.0211

0.87 0.83

0.0231 0.0214



Article

volumes of these three amino acids increase in this order: ΔtrVφ0 (glycine) > ΔtrVφ0 (L-alanine) > ΔtrVφ0 (L-valine) except for a 0.2000 mol·kg−1 xylitol aqueous solution. The ΔtrVφ0 of L-arginine and L-threonine are approximate and depend on the hydrophilic groups. Therefore, the transfer volumes of amino acids increase with increasing the xylitol concentration and the temperature except for glycine. This situation is similar to sorbitol.11 The limiting partial molar volume Vφ0 consists of two parts: intrinsic volume of the solute and the changed volume due to the interaction between the solute−solvent.29 Intrinsic volume of the solute could be expressed as

Table 5. continued T/(K)

B/(dm3·mol−1)

313.15 323.15

0.493 ± 0.474 ±

293.15 303.15 313.15 323.15

0.553 0.528 0.507 0.486

± ± ± ±

293.15 303.15 313.15 323.15

0.567 0.543 0.520 0.503

± ± ± ±

D/(dm6·mol−2)

mb = 0.6000 mol·kg−1 0.003 0.309 ± 0.006 0.005 0.267 ± 0.010 mb = 0.8000 mol·kg−1 0.002 0.372 ± 0.003 0.001 0.355 ± 0.003 0.002 0.299 ± 0.004 0.004 0.281 ± 0.007 mb = 1.0000 mol·kg−1 0.008 0.397 ± 0.014 0.005 0.341 ± 0.010 0.004 0.313 ± 0.008 0.007 0.274 ± 0.013

100AD

SD/mPa·s

0.74 0.70

0.0200 0.0186

0.80 0.66 0.65 0.64

0.0203 0.0182 0.0172 0.0160

0.65 0.64 0.56 0.54

0.0178 0.0161 0.0150 0.0140

Vint = VvW + Vvoid

where, VvW represents the van der Waals volume occupied by the solute, Vvoid is the volume associated with the void and empty space present therein.30 To further evaluate the contribution of a solute molecule to its limiting partial molar volume, the equation could be modified by Shahidi et al.31 as follows:

The order of Vφ0 of amino acids is the same as the order of Vφ. In addition, the limiting partial molar volumes increase with the increase of xylitol concentration and the temperature. The increase in temperature could weaken the binding of the solvent molecules from the terminal zwitterions of amino acids, releasing solvent molecules into the bulk and accordingly leading to an expansion of volume. 3.1.2. Limiting Partial Molar Volume of Transfer. Transfer properties could provide qualitative information on the interaction between solvent and solute without considering the effect of solute and solute interaction.24 To further investigate the interactions of the amino acids in the xylitol aqueous solutions, we calculate the transfer partial molar volumes (ΔtrVφ0)25 as follows: Δtr Vφ 0 = Vφ 0[xylitol + water] − Vφ 0[water]

(5)

V φ0 = VvW + Vvoid − nσS

(6)

where σS denotes the shrinkage in the volume owing to the interaction of hydrogen bonding between the solute and water molecules, and n is the number of hydrogen bonding sites. Thus, the Vφ0 of amino acids could be expressed as V φ0 = VvW + Vvoid − Vshrinkage

(7) 32−34

Assuming that VvW and Vvoid are not affected by xylitol, the positive Vφ0 is attributed to a decrease of the shrinkage volume because of the presence of xylitol molecules. The positive ΔtrVφ0 could be explained by the decreased shrinkage volume resulting from the decrease of electrostatic interactions presenting in amino acids and water molecules. Therefore, more water molecules from the hydration shell are released into the bulk water. 3.2. Viscometric Properties. Viscosity B coefficient is an empirical constant, depending on the relative size of the solute and solvent molecules.35 The variation of viscosity B coefficient with temperature could help us distinguishing the role of solute as structure-breaker or maker in the solvent media.36,37 The viscosity B coefficient is computed through the extended Jones−Dole equation38 as follows:

(4)

The transfer partial molar volumes are given in Table 4. To understand the interaction between the solute−solvent, the cosphere overlap model is utilized to analyze the transfer volume.26−28 According to this model, there are mainly five interactions existing between amino acid and xylitol molecules: (a) Ion-hydrophilic interaction between the zwitterionic groups (NH3+, COO−) of amino acid and the hydrophilic OH groups of xylitol; (b) hydrophilic−hydrophilic interaction between the hydrophilic groups of amino acid and the OH groups of xylitol; (c) ion-hydrophobic interaction between the zwitterionic groups (NH3+, COO−) of amino acid and the alkyl chain of xylitol; (d) hydrophobic−hydrophobic interaction between the alkyl chain of amino acid and the alkyl chain of xylitol; (e) hydrophobic−hydrophilic interaction between the alkyl chain of amino acid and the OH groups of xylitol, and the hydrophilic groups of amino acid and the alkyl chain of xylitol. For these five interactions, (a) and (b) produce positive contribution to volume. For type (a), the overlap of the groups (NH3+, COO−) of amino acid molecules and xylitol molecules lead to a decrease in the electrostriction of water molecules lying in the proximity of amino acid molecules, some water molecules could be released into bulk water. For type (b), hydrogen bonding between the hydrophilic group of amino acid and OH of xylitol decreases the interaction of hydrophilic solute and water, finally leading to a positive contribution to transfer volume. On contrast, the interactions of type (c), (d), and (e) would decrease ΔtrVφ0 in light of their cosphere overlap. For glycine, L-alanine, and L-valine, the interactions (a), (c), (d), and (e) exist in solutions. The positive ΔtrVφ0 values indicate the predominance of ion−hydrophilic interaction. The transfer

ηr = η /η0 = 1 + BC + DC 2

(8)

Where ηr is the relative viscosity, C is the molar concentration of amino acid in xylitol aqueous solution at 293.15 K, and η and η0 are the viscosities of the ternary solution and the xylitol aqueous solution, respectively. At a given temperature the parameters B and D are the constants as shown in Table 5. From Table 5 it could be clearly seen that the values of B coefficient for all the amino acids in aqueous xylitol solutions at (293.15 to 323.15) K are positive, indicating the strong solute− solvent interaction. It is interesting that the B coefficients of glycine increase with the temperature, but for other four amino acids, the B coefficients decrease with increasing temperature at a given concentration of xylitol. The positive dB/dT indicates that the solute prefers to be structure-breaker, while the negative dB/dT represents structure-maker. In the system studied, the positive values of dB/dT for glycine over the whole temperature range show that glycine is structure-breaker, whereas the rest of amino acids with negative dB/dT values behave as structuremakers. K



Article

Table 6. Free energies of Activation per Mole for Solvent (Δμ10⧧) and Solute (Δμ20⧧), Hydration Number (nH) of Amino Acid in Xylitol Aqueous Solution at T = (293.15, 303.15, 313.15 and 323.15) K ma/mol·kg−1 0.2000

0.4000

0.6000

0.8000

1.0000

0.2000

0.4000

0.6000

0.8000

1.0000

0.2000

0.4000

0.6000

T/K 293.15 303.15 313.15 323.15 293.15 303.15 313.15 323.15 293.15 303.15 313.15 323.15 293.15 303.15 313.15 323.15 293.15 303.15 313.15 323.15 293.15 303.15 313.15 323.15 293.15 303.15 313.15 323.15 293.15 303.15 313.15 323.15 293.15 303.15 313.15 323.15 293.15 303.15 313.15 323.15 293.15 303.15 313.15 323.15 293.15 303.15 313.15 323.15 293.15 303.15

Δμ10⧧/kJ·mol−1 Glycine 9.51 9.26 9.04 8.86 9.73 9.47 9.25 9.06 9.95 9.69 9.46 9.27 10.17 9.92 9.69 9.49 10.37 10.12 9.88 9.68 L-Alanine 9.51 9.26 9.04 8.86 9.73 9.47 9.25 9.06 9.95 9.69 9.46 9.27 10.17 9.92 9.69 9.49 10.37 10.12 9.88 9.68 L-Valine 9.51 9.26 9.04 8.86 9.73 9.47 9.25 9.06 9.95 9.69

Δμ20⧧/kJ·mol−1

ma/mol·kg−1

nH

T/K



nH

67.42 64.98 72.16 69.95 69.61 66.62 74.90 70.31 70.60 67.96

3.84 3.50 4.62 4.25 4.06 3.67 4.92 4.34 4.20 3.84

60.82 59.97 59.55 56.56 62.18 60.87 60.56 57.29 63.58 62.69 61.90 58.75 64.77 63.00 62.23 59.40 66.52 63.23 62.31 59.95

4.28 4.03 3.83 3.43 4.46 4.16 3.96 3.53 4.66 4.39 4.15 3.71 4.82 4.45 4.21 3.80 5.04 4.52 4.27 3.89

88.85 88.60 88.22 86.36 89.76 89.20 88.65 88.49 91.23 90.73 88.88 88.71 91.64 91.06 89.34 89.19 93.75 91.48 89.90 89.31

3.97 3.79 3.61 3.36 4.08 3.87 3.68 3.53 4.23 4.02 3.75 3.60 4.31 4.10 3.84 3.68 4.51 4.18 3.92 3.74

L-Valine

25.09 25.69 26.88 28.13 25.86 27.13 27.99 28.59 26.88 28.14 29.33 30.14 27.59 28.85 30.43 31.53 29.14 30.54 31.87 33.26

2.16 2.18 2.30 2.42 2.27 2.41 2.46 2.48 2.46 2.59 2.70 2.74 2.59 2.72 2.89 2.98 2.88 3.03 3.16 3.28

39.73 39.63 38.63 37.14 40.76 39.92 39.19 39.34 42.28 40.21 39.43 39.74 42.48 40.39 39.79 39.97 44.04 42.21 40.60 40.33

3.08 2.95 2.73 2.46 3.23 3.00 2.81 2.73 3.46 3.07 2.87 2.81 3.52 3.12 2.94 2.86 3.75 3.38 3.07 2.93

65.92 64.99 64.84 61.19 69.18 66.69 66.00 64.73 69.78 68.75

3.91 3.68 3.53 3.12 4.24 3.88 3.67 3.44 4.35 4.10

0.8000

1.0000

0.2000

0.4000

0.6000

0.8000

1.0000

0.2000

0.4000

0.6000

0.8000

1.0000

313.15 323.15 293.15 303.15 313.15 323.15 293.15 303.15 313.15 323.15 293.15 303.15 313.15 323.15 293.15 303.15 313.15 323.15 293.15 303.15 313.15 323.15 293.15 303.15 313.15 323.15 293.15 303.15 313.15 323.15 293.15 303.15 313.15 323.15 293.15 303.15 313.15 323.15 293.15 303.15 313.15 323.15 293.15 303.15 313.15 323.15 293.15 303.15 313.15 323.15

9.46 9.27 10.17 9.92 9.69 9.49 10.37 10.12 9.88 9.68 L-Threonine 9.51 9.26 9.04 8.86 9.73 9.47 9.25 9.06 9.95 9.69 9.46 9.27 10.17 9.92 9.69 9.49 10.37 10.12 9.88 9.68 L-Arginine 9.51 9.26 9.04 8.86 9.73 9.47 9.25 9.06 9.95 9.69 9.46 9.27 10.17 9.92 9.69 9.49 10.37 10.12 9.88 9.68

where V̅ 01 (= ∑xiMi/ρ0) and V̅ 02 (= Vφ0) denote the molar volume of the solvent (xylitol + water) and the limiting partial molar volume of the solute, respectively. ρ0 is the density of the binary solvent. The xi and Mi are the mole fraction and molar weight of water and xylitol in mixed solvent, respectively. The free energy of activation per

The viscosities were also analyzed based on the transition state theory proposed by Feakins et al.39,40 According to the theory, the B coefficient could be given as follows: B = (V1̅ 0 − V2̅ 0)/1000 + V1̅ 0(Δμ20 ⧧ − Δμ10 ⧧ )/1000RT (9) L



■

mole of solvent Δμ10⧧ could be calculated by the following equation:41 Δμ10 ⧧ = RT ln(η0V1̅ 0/hNA )

*E-mail: [email protected]. *E-mail: [email protected].

(10)

ORCID

Chunying Zhu: 0000-0002-3520-8392 Notes

The authors declare no competing financial interest.

■

(11)

Similarly, for the system in this work, the free energies of activation per mole of amino acid and the mixed solvent are all positive from Table 6, and Δμ20⧧ are much larger than Δμ10⧧, this indicates that the existence of amino acid could hinder the formation of the transition state, accompanied by formation of ion−solvent bond and the collapse of the solvent−solvent bond. At a certain temperature and concentration, the free energy of activation per mole of amino acid increases in this order: Δμ20⧧ (glycine) < Δμ20⧧ (L-alanine) < Δμ20⧧ (L-threonine) < Δμ20⧧ (L-valine) < Δμ20⧧ (L-arginine); this is in line with the order of the viscosity of five amino acids. The larger the viscosity value is, the more difficult it is to form the transition state. In addition, the free energies of activation per mole of glycine are smallest, thus glycine tends to behave as a structure-breaker in the xylitol solution. 3.3. Hydration Number. The hydration number, nH of amino acid in aqueous xylitol solution could be calculated through the viscosity B-coefficient and the limiting partial molar volume using the relation:42,43 nH = B /V φ0

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Corresponding Authors

where h and NA are Planck’s constant and Avogadro’s number, respectively. R is gas constant, and η0 is the viscosity of the solvent. If we rearrange eq 9, the free energy of activation per mole of solute Δμ20⧧ could be obtained:41 Δμ20 ⧧ = Δμ10 ⧧ + RT[1000B − (V1̅ 0 − V2̅ 0)]/V1̅ 0

Article

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(12)

The hydration number could be affected by many factors, at a certain temperature and the external force, there are two main aspects: one is the volume size of molecule, and the other is the molecular polarity. In Table 6, the hydration numbers of five amino acids increase with the xylitol concentration. In addition, the hydration numbers decrease with the rise of temperature except glycine. From the overall comparison, the hydration numbers of L-valine, L-threonine, and L-arginine are greater than glycine and L-alanine, the polarity and molecular volume of the former three amino acids are larger, thus the solute molecules could adsorb more water molecules in the solvation shell.

4. CONCLUSIONS In this study, the densities and viscosities for glycine, L-alanine, L-valine, L-threonine, and L-arginine in aqueous xylitol solutions were measured at T = (293.15, 303.15, 313.15, and 323.15) K. The apparent molar volume Vφ, the limiting partial molar volume Vφ0, and limiting partial molar volume of transfer ΔtrVφ0 were determined. Both the values of Vφ and Vφ0 for five amino acids increase in the order: glycine < L-alanine < L-threonine < L-valine < L-arginine, and the positive ΔtrVφ0 suggests the dominance of ion−hydrophilic and hydrophilic−hydrophilic interactions over other three hydrophobic interactions. The experimental viscosities were correlated using the extended Jones-Dole equation to obtain the viscosity B coefficients. Successively, the free energies of activation per mole of solvent Δμ10⧧ and solute Δμ20⧧ and hydration number nH were calculated. The analysis on both volumetric and viscometric properties indicates that glycine in xylitol aqueous solution acts as a structure-breaker, while L-alanine, L-valine, L-threonine, and L-arginine like to act as structure-makers. M



Article

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Densities and Viscosities of Amino Acid + Xylitol + Water Solutions at

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