Investigations to explore interactions in (polyhydroxy solute + l -ascorbic acid + H2O) solutions at different temperatures: Calorimetric and viscometric approach

J. Chem. Thermodynamics 102 (2016) 322–332

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Investigations to explore interactions in (polyhydroxy solute + L-ascorbic acid + H2O) solutions at different temperatures: Calorimetric and viscometric approach Parampaul K. Banipal ⇑, Mousmee Sharma, Neha Aggarwal, Tarlok S. Banipal Department of Chemistry, Guru Nanak Dev University, Amritsar 143005, India

a r t i c l e

i n f o

Article history: Received 29 December 2015 Received in revised form 4 July 2016 Accepted 15 July 2016 Available online 18 July 2016 Keywords: L-ascorbic acid Saccharide Limiting enthalpy of dilution Viscosity B-coefficient Isothermal titration calorimetry

a b s t r a c t Isothermal titration micro-calorimeter has been used to measure the enthalpy change (q) of polyhydroxy solutes [(+)-D-xylose, xylitol, (+)-D-glucose, 2-deoxy-D-glucose, (+)-methyl-a-D-glucopyranoside, and (+)maltose monohydrate] in water and in (0.05, 0.15, and 0.25) mol
kg1 L-ascorbic acid(aq) solutions at (288.15, 298.15, 308.15, and 318.15) K. Limiting enthalpies of dilution (DdilH°) of these solutes were calculated from heat evolved/absorbed during calorimetric experiments. Further thermodynamic quantities such as limiting enthalpies of dilution of transfer (DtrDdilH°), change in heat capacity (DdilCop,2,m), and pair (hAB) and triplet (hABB) enthalpic interaction coefficients were also calculated and used to explore the nature of interactions of solutes with cosolute (L-ascorbic acid). The Jones-Dole viscosity B-coefficients for (+)-D-xylose, xylitol, (+)-D-galactose, galactitol, (+)-D-glucose, 2-deoxy-D-glucose, (+)-methyl-a-Dglucopyranoside, and (+)-maltose monohydrate in water and in (0.05, 0.15, 0.25, and 0.35) mol
kg1 L-ascorbic acid(aq) solutions have been determined from viscosity (g) data measured over temperature range (288.15–318.15) K and at pressure, P = 101.3 kPa. The temperature dependence of B-coefficients (dB/dT), and viscosity B-coefficients of transfer (DtrB) of solutes from water to cosolute have also been estimated. These parameters have been discussed in terms of structure-making (kosmotropic) or -breaking (chaotropic) behavior of solutes. Ó 2016 Elsevier Ltd.

1. Introduction Saccharides and their derivatives are the most abundant class of biomolecules, known for biological versatility and great diversity of their biological functions [1–4]. Disaccharides can stabilize the labile biomolecules by a combination of kinetic and specific effects in aqueous solutions. During lyophilisation process, disaccharides are used as cryoprotectants against the destabilizing and degradation of drugs and enzymes [5–8]. Sugar alcohols are alternative artificial nutritive sweeteners and have been widely used in food and beverages due to their properties of good taste, low calorie content and no tooth decay. Additionally, they are also applied in many aspects like pharmacy, cosmetics, explosives, and plasticizers, etc [9–14]. As a kind of polyhydroxy compounds, L-ascorbic acid is an ubiquitous and indispensable compound in living systems, required for the metabolism of folic acids and mineral compounds. L-ascorbic acid is essential to synthesize collagen which provides the structure to muscles, bones, and tendon. The most ⇑ Corresponding author. E-mail address: [email protected] (P.K. Banipal). http://dx.doi.org/10.1016/j.jct.2016.07.020 0021-9614/Ó 2016 Elsevier Ltd.

prominent role of L-ascorbic acid is its immune stimulating effect for defense against infections such as common colds. It acts as an inhibitor of histamine released during allergic reactions. As a powerful antioxidant, L-ascorbic acid can neutralize toxins and pollutants. It has an ability to prevent the formation of potentially carcinogenic nitrosamines in the stomach. L-ascorbic acid along with Zn are important for healing the wounds [15–16]. The degradation of L-ascorbic acid is very important and major cause of quality and color changes during storage of food materials [17]. Thermodynamic and transport studies of aqueous solutions of polyhydroxy solutes are significant because of their multidimensional physical, biochemical, and industrially useful properties. Terekhova et al. [18] reported the enthalpies of solutions of few saccharides in L-ascorbic acid at 298.15 K only. Banipal et al. [19] reported the volumetric, isentropic compressibility and viscometric properties of various vitamins; L-ascorbic acid, nicotinic acid, thiamine hydrochloride, and pyridoxine hydrochloride in water at (288.15, 298.15, 308.15 and 318.15) K. Recently, we have reported [20] the volumetric and UV absorption studies in order to understand the solvation behavior of polyhydroxy solutes in L-ascorbic acid(aq) solutions at T = (288.15–318.15) K. In the current

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study, calorimetric and viscometric properties have been exploited to understand the mode of interaction of polyhydroxy solute with acid. Various quantities such as limiting enthalpy of dilution, heat capacity change, Jones-Dole viscosity B-coefficients, and interaction coefficients for solutes have been estimated in water and in different molalities of L-ascorbic acid(aq) solutions. An attempt has been made to examine the concentration and temperature dependence of these outcomes.

were also performed and appropriate corrections were made to the main experiment.

L-ascorbic

2.3. Viscosity The viscosities (g) of solutes in water and mB = (0.05, 0.15, 0.25 and 0.35) mol
kg–1 L-ascorbic acid(aq) solutions have been determined from efflux time, t measurements at T = (288.15, 298.15, 308.15, and 318.15) K as:

g=q ¼ at  b=t

2. Experimental 2.1. Materials The provenances including mass fraction purity, CAS number, source of procurement and abbreviations of the chemicals used are presented in Table 1. The purity of the chemicals used was analyzed with C, H, N, S analysis method using FLASH 2000 Organic Elemental Analyzer, USA. The carbon and hydrogen contents obtained in the analysis are similar to expected values from molecular formula with zero percentage of sulfur and nitrogen (Table 1). These chemicals were used after drying over CaCl2(anhyd) in a vacuum desiccator for 48 h at room temperature. The solutions were prepared fresh on mass basis in air tight glass vials by using Mettler-Toledo balance (Model: AB 265-S) having a precision of ±0.01 mg. Pure water with specific conductance less than 1.29  10–4 S
m–1 was procured from Ultra UV/UF Rions lab water system. It was degassed before use to avoid microbubbles in solutions. 2.2. Isothermal titration calorimetry The measurement of enthalpy change for the studied systems was carried out on an isothermal titration micro-calorimeter (MicroCal iTC200, USA) at T = (288.15, 298.15, 308.15 and 318.15) K. The reference cell was filled with pure water and the sample cell with a capacity of 200 ll was filled with water or cosolute solution. Titrations were carried out using a 40 ll syringe filled with 0.25 mol
kg–1 solute solution, stirring at a speed of 500 rpm during each run. The titration experiment was consisting of 19 consecutive injections of 2 ll each and having duration 4 s with an interval of 120 s between consecutive injections. The control experiments

ð1Þ

where q is the density of solution (reported earlier [20]); a and b are the viscometric constants. The viscosities (g) of solutions were measured by using an Ubbelohde-type capillary viscometer, calibrated by measuring the efflux time of water from T = (288.15–318.15) K. The efflux time was measured with a digital stopwatch with a resolution of ±0.01 s for the average of at least four flow-time readings. The temperature of the experimental solution was controlled within ±0.01 K using an efficient constant temperature bath (Julabo F-25). The measured uncertainty in viscosity is ±0.02 mPa
s which also includes the uncertainty in viscosity of calibrated solvent i.e. water. The viscosities for pure water taken from the literature are (1.1382, 0.8904, 0.7194, 0.5963) mPa
s at (288.15, 298.15, 308.15, and 318.15) K, respectively [21,22]. 3. Results and discussion 3.1. Limiting enthalpy of dilution The enthalpy change (q) was measured for some polyhydroxy solutes in water and in mB (molality of L-ascorbic acid) = (0.05, 0.15 and 0.25) mol
kg–1 L-ascorbic acid(aq) solutions (data are given as supplementary material in Table S1). The process is exothermic and the magnitude of q values decreases with increase in molalities of solute. Overall the enthalpy change was found to be less exothermic with rise of temperature, whereas it increases for Glc, Mal and Xyol in water and for Xyol in mB  0.05 mol
kg1 too. A representative 3-D plot of q versus mA, molality of 2de-Glc in mB = 0.15 mol
kg1 L-ascorbic acid(aq) solutions is given in Fig. 1, over the temperature range (288.15–318.15) K. The comparison of data (Fig. 2a) shows that the enthalpy change for derivative; Me a-Glc is more exothermic in water as compared to its parent

Table 1 Specifications of chemicals used.

a

Compound (abbreviation) [Molecular Formula]

Molar mass (g
mol–1)

Mass fraction puritya

Source

CAS number

L-Ascorbic

176.12

P0.99

Sigma Chemical Co.

50-81-7

(+)-D-Xylose (Xyl)[C5H10O5]

150.13

P0.99

Sigma Chemical Co.

58-86-6

Xylitol (Xyol) [C5H12O5]

152.15

P0.99

Sisco Research Lab.

87–99-0

(+)-D-Galactose (Gal) [C6H12O6]

180.16

0.98

Sisco Research Lab.

59-23-4

Galactitol (Gaol) [C6H14O6]

182.18

0.99

Sisco Research Lab.

608-66-2

(+)-D-Glucose (Glc) [C6H12O6]

180.16

P0.99

Sigma Chemical Co.

50–99-7

2-Deoxy-D-glucose (2de-Glc) [C6H12O5]

164.16

0.99

Sisco Research Lab.

154-17-6

(+)-Methyl-a-D-glucopyranoside (Me a-Glc) [C7H14O6]

194.18

P0.99

Sigma Chemical Co.

97-30-3

(+)-Maltose monohydrate (Mal) [C12H22O11
H2O]

360.31

0.99

Sigma Chemical Co.

6363-53-7

Acid [C6H8O6]

As reported by the suppliers.

C, H, N, S analysis Calculated%

Observed%

C = 40.88 H = 4.54 C = 40.00 H = 6.71 C = 39.43 H = 7.89 C = 39.96 H = 6.66 C = 39.52 H = 7.68 C = 40.00 H = 6.71 C = 43.90 H = 7.37 C = 43.30 H = 7.27 C = 40.00 H = 6.71

C = 40.85 H = 4.57 C = 39.97 H = 6.69 C = 39.45 H = 7.87 C = 40.03 H = 6.63 C = 39.55 H = 7.65 C = 40.03 H = 6.69 C = 43.88 H = 7.39 C = 43.27 H = 7.25 C = 40.02 H = 6.69

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0 -20

-160 -140 -120 -100 -80 -60 -40 -20 0

-40

q/J.mol

-1

-60 -80 -100 -120 -140 -160 310 305

T/ K

300 295 290 5

10

25

30

35

40

-1 ol.kg m / 10 m A.

15

20

3

Fig. 1. Plot of enthalpy change (q) versus molality (mA) of 2-deoxy-D-glucose in mB = 0.15 mol
kg–1 of L-ascorbic acid as a function of temperature.

(a)

0

10

20

30

40

(b)

0

10

20

30

40

0

Glc

Xyol 288.15 K

288.15 K

-10

-60 -110

318.15 K

-160

q/J·mol–1

q/J·mol–1

-20 -30

318.15 K

-40 -50 -60

-210

288.15 K Me α-Glc

(c)

0

10

20

30

mA·103/mol·kg–1

-80

mA·103/mol·kg–1

-260

Xyl 288.15 K

-70

40

(d)

0

0

10

20

30

40

0

-10

-20

q/J·mol–1

q/J·mol–1

-20 -30 -40 -50

-40 -60 -80

-60 -100

-70 -80

mA·103/mol·kg–1

-120

mA·103/mol·kg–1

Fig. 2. The enthalpy change (q) versus molalities (mA) of solutes; {a}(+)-D-glucose {r; j; N; } and (+)-methyl-a-D-glucopyranoside {⁄; d; +; } in water, {b} (+)-D-xylose {r; j; N; } and xylitol {⁄; d; +; } in water; {c}(+)-D-glucose {r; j; N; } and (+)-methyl-a-D-glucopyranoside {⁄; d; +; } in mB = 0.25 mol
kg–1 of L-ascorbic acid, {d} (+)-Dxylose {r; j; N; } and xylitol {⁄; d; +; } in mB = 0.25 mol
kg–1 of L-ascorbic acid at T = 288.15 K {r; ⁄}, 298.15 K {j; d}, 308.15 K {N; +} and 318.15 K {; }.

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(b) 160

(a) 300

140 250

-q/J·mol–1

-q/J·mol–1

120 200 150

100 80 60

100

40 50

20 0

0 -5

5

15

25

35

-5

45

mA·103/mol·kg–1

5

15

25

35

45

mA·103/mol·kg–1

Fig. 3. The enthalpy change (q) versus molalities (mA) of solutes; (+)-D-xylose; r, xylitol; j, (+)-D-glucose; N, 2-deoxy-D-glucose; , (+)-methyl-a-D-glucopyranoside; ⁄, (+)maltose monohydrate; d in (a) water and (b) in mB = 0.15 mol
kg–1 of L-ascorbic acid at T = 298.15 K.

saccharide i.e., Glc. In contrast, the enthalpy change is less exothermic for Xyol than its respective saccharide i.e., Xyl (Fig. 2b), suggesting that pentose disrupts the water structure to the larger extent as compared to pentaol. Further the difference in q values between Xyl and Xyol, and between Glc and its derivative is large in water and this difference becomes very small at higher molalities of cosolute at all temperatures (Fig. 2c, d). The exothermicity for the studied solutes in water follows the order: Xyol < Xyl < Glc < Mal < 2de-Glc < Me a-Glc at all temperatures. A

representative plot of q versus mA, molality of solutes in water and in mB = 0.15 mol
kg1 L-ascorbic acid(aq) at T = 298.15 K is given in Fig. 3(a, b), respectively. The q values for studied solutes in mB  0.05 mol
kg1 L-ascorbic acid follow the order: Xyol < Glc < Xyl < Mal < 2de-Glc < Me a-Glc at 288.15 K, whereas Xyol < Glc < Xyl < 2de-Glc < Mal < Me a-Glc at (298.15–318.15) K, indicating that the q values of Me a-Glc are largest. With increase in the concentration of L-ascorbic acid up to mB  0.25 mol
kg1, the q values for Me a-Glc are observed to be lowest among the studied solutes,

Table 2 Limiting enthalpies of dilution (DdilH°) of polyhydroxy solutes in L-ascorbic acid(aq) solutions from T = (288.15–318.15) K and P = 101.3 kPa. a

mB/(mol
kg1)

Ddil H°/(J
mol1) T/(K) = 288.15

298.15

308.15

318.15

(+)-D-Xylose 0.00 0.05 0.15 0.25

77.69 ± 0.88 91.05 ± 0.85 98.70 ± 1.19 103.31 ± 0.32

74.21 ± 0.81 78.87 ± 1.39 73.14 ± 0.95 61.61 ± 1.06

67.17 ± 0.97 66.84 ± 1.02 50.10 ± 0.62 39.41 ± 0.95

65.04 ± 0.83 62.39 ± 0.84 40.13 ± 0.45 22.68 ± 0.33

Xylitol 0.00 0.05 0.15 0.25

12.42 ± 0.14 20.26 ± 0.48 43.30 ± 0.22 81.12 ± 0.68

22.66 ± 0.28 25.40 ± 0.47 31.35 ± 0.38 55.56 ± 0.53

30.71 ± 0.57 29.54 ± 0.35 28.91 ± 0.28 41.46 ± 0.50

43.68 ± 0.38 34.37 ± 0.33 26.11 ± 0.31 33.83 ± 0.90

(+)-D-Glucose 0.00 0.05 0.15 0.25

70.72 ± 0.53 75.91 ± 0.51 77.46 ± 0.61 76.60 ± 0.72

78.38 ± 1.09 72.34 ± 0.42 52.33 ± 0.33 43.12 ± 0.55

81.41 ± 0.81 68.23 ± 0.84 38.82 ± 0.65 17.79 ± 0.40

87.21 ± 0.60 54.76 ± 0.41 21.28 ± 0.46 -5.80 ± 0.19

2-Deoxy-D-glucose 0.00 0.05 0.15 0.25

159.84 ± 0.65 167.16 ± 2.21 151.26 ± 2.16 143.33 ± 2.23

145.38 ± 0.81 120.76 ± 0.88 94.74 ± 0.52 77.77 ± 1.51

122.28 ± 0.62 82.01 ± 0.59 53.01 ± 0.75 30.66 ± 0.64

104.96 ± 0.40 75.07 ± 0.89 41.97 ± 0.63 14.10 ± 0.35

(+)-Methyl-a-D-glucopyranoside 0.00 0.05 0.15 0.25

254.97 ± 1.14 216.59 ± 1.41 137.49 ± 0.78 46.10 ± 0.54

246.32 ± 1.66 208.37 ± 1.31 115.05 ± 0.93 34.76 ± 0.54

223.06 ± 1.02 192.91 ± 1.36 104.60 ± 1.38 28.85 ± 0.70

209.27 ± 1.23 166.41 ± 2.15 99.17 ± 1.59 23.98 ± 0.27

(+)-Maltose monohydrate 0.00 0.05 0.15 0.25

76.27 ± 0.52 134.64 ± 0.61 160.65 ± 0.81 212.49 ± 1.44

118.98 ± 1.85 132.72 ± 1.41 145.50 ± 1.00 181.27 ± 1.55

140.26 ± 1.17 118.36 ± 1.02 133.52 ± 1.60 151.03 ± 1.20

146.34 ± 0.48 110.30 ± 0.54 129.37 ± 1.53 146.75 ± 1.72

Standard uncertainties, u are: u(T) = ±0.01 K, u(P) = ±0.5 kPa (Level of confidence is 0.68). a mB/(mol
kg–1) = molality of L-ascorbic acid.

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(a) 50

(b) 30

Xyl

30 20 10 0 -10

0

0.05

0.1

0.15

0.2

0.25

∆trΔdilH °/J·mol–1

∆trΔdilH °/J·mol–1

40

-20 -30

mB/mol·kg–1 Glc

80 70 60 50 40 30 20 10 0 -10 0 -20

0.15

0.2

0.25

0.2

0.25

mB/mol·kg–1

2de-Glc

80 60 40 20

0.1

0.15

0.2

0.25

0

Me α-Glc

150 100 50 0 0.1

0.15

0.1

40 20 0 -20 0 -40 -60 -80 -100 -120 -140 -160

0.2

0.25

0.15

mB/mol·kg–1

(f) 60

200

0.05

0.05

-20

mB/mol·kg–1

∆trΔdilH °/J·mol–1

∆trΔdilH °/J·mol–1

0.1

0 0.05

(e) 250

0

0.05

(d) 100 ∆trΔdilH °/J·mol–1

∆trΔdilH °/J·mol–1

(c) 90

Xyol

20 10 0 -10 0 -20 -30 -40 -50 -60 -70 -80

Mal

0.05

mB/mol·kg–1

0.1

0.15

0.2

0.25

mB/mol·kg–1

Fig. 4. Limiting enthalpy of transfer (DtrDdilH°) versus molalities (mB) of L-ascorbic acid for (a) (+)-D-xylose (b) xylitol (c) (+)-D-glucose (d) 2-deoxy-D-glucose (e) (+)-methyl aD-glucopyranoside (f) (+)-maltose monohydrate at r, 288.15 K; j, 298.15 K; N, 308.15 K; , 318.15 K.

Table 3 The heat capacity change (DdilCvp,2,m) of polyhydroxy solutes in L-ascorbic acid(aq) solutions at T = (288.15–318.15) K and P = 101.3 kPa. a

mB/(mol
kg1)

T/(K) = 288.15

298.15

308.15

mB/(mol
kg1)

T/(K) = 288.15

298.15

308.15

318.15

0.35 0.40 0.82 0.77

0.81 0.49 1.23 2.90

0.95 0.47 0.77 2.01

1.09 0.46 0.31 1.11

1.22 0.44 0.15 0.21

0.53 0.68 1.63 1.84

0.53 0.68 1.25 0.77

2-Deoxy-D-glucose 0.00⁄ 0.05 0.15 0.25

1.88 6.11 7.11 8.02

1.88 4.14 4.83 5.57

1.88 2.16 2.56 3.12

1.88 0.19 0.29 0.67

1.73 1.66 1.25 0.56

1.99 1.66 1.25 0.24

(+)-Maltose monohydrate 0.00 5.06 0.05⁄ 0.87 0.15 1.88 0.25 4.30

3.23 0.87 1.33 2.95

1.40 0.87 0.78 1.60

0.43 0.87 0.23 0.25

0.55 1.56 3.16 4.51

0.48 1.17 2.38 3.27

0.42 0.79 1.60 2.02

(+)-D-Glucose 0.00⁄ 0.05⁄ 0.15 0.25

0.53 0.68 2.39 3.99

0.53 0.68 2.01 2.91 1.48 1.66 1.25 0.88

(+)-Methyl-a-D-glucopyranoside 0.00 1.22 0.05⁄ 1.66 ⁄ 0.15 1.25 0.25 1.21

a

Xylitol 0.00 0.05 0.15 0.25

(+)-D-Xylose 0.00 0.05 0.15 0.25

318.15

Standard uncertainties, u are: u(T) = ±0.01 K, u(P) = ±0.5 kPa (Level of confidence is 0.68). Errors in the heat capacity change lie in the range of (0.84–4.10) J
K1
mol1. a mB/(mol
kg–1) = molality of L-ascorbic acid.

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1.4

mPa.s

1.2 1.0

0.4 0.6 0.8 1.0 1.2 1.4

0.8 0.6 0.4 0.14 0.12 A /m 0.10 ol. kg -1 0.08 0.06

m

315

310

305

300

295

290

T/K

Fig. 5. Plot of viscosity (g) versus molality (mA) of (+)-D-glucose in mB = 0.05 mol
kg–1 of L-ascorbic acid as a function of temperature.

except at (308.15 and 318.15) K, where q values for Me a-Glc are higher than Glc. This indicates the significant effect of cosolute molality, mB as well as temperature on q values of the solutes. The limiting enthalpy of dilution (DdilH°) of each polyhydroxy solute was calculated by fitting the following equation to the respective data for q values obtained at each temperature:

q ¼ Ddil H þ mA Sv

ð2Þ

where Sv is the empirical slope. The DdilH° values for the studied solutes are negative (Table 2) again reflecting that the solutesolvent/cosolute interactions are accompanied by an exothermic process. Generally, the DdilH° values tend to be less exothermic with increase in molalities of cosolute but in cases of Xyl (only at 288.15 K), Xyol and Mal, the exothermicity increases with increase in mB values. With rise of temperature, the DdilH° values also become less exothermic except for Xyol, Glc and Mal in water and for Xyol in mB  0.05 mol
kg1 L-ascorbic acid(aq) too. The limiting enthalpies of dilution of transfer of solutes from water to L-ascorbic acid(aq) were calculated as:

Dtr Ddil H° ¼ Ddil H°fn L-ascorbic acidðaqÞ solutionsg  Ddil H°fin H2 OðlÞ g

ð3Þ

Both positive and negative DtrDdilH° values have been observed for studied polyhydroxy solutes (Fig. 4). In Glc and 2de-Glc, the DtrDdilH° values are positive at (298.15, 308.15 and 318.15) K and their magnitude increase with increase in mB values, while at 288.15 K, the negative DtrDdilH° values in the lower concentration (below 0.1 mol
kg–1) of L-ascorbic acid(aq) become positive at higher mB values in case of 2de-Glc but remain continuously negative at all mB values in Glc. In case of Xyl, the magnitude of negative DtrDdilH° values increase with increase in mB values at 288.15 K, however, at higher temperatures and mB values, the magnitude of DtrDdilH° values become positive. In Xyol and Mal, the DtrDdilH° values are negative at (288.15 and 298.15) K and their magnitudes increase with mB values, however, positive DtrDdilH° values at (308.15 and 318.15) K start decreasing with increase in mB after passing through maxima become negative at higher mB values. In Me a-Glc, the DtrDdilH° values are large positive at all temperatures and vary linearly with increase in molalities of

cosolute. These results indicate that transfer of solutes (except Me a-Glc) from water to L-ascorbic acid(aq) is more exothermic at low temperatures rather than at higher temperatures. In aqueous solutions of polyhydroxy solute and L-ascorbic acid, the following three kinds of interactions contribute to the observed value of enthalply of dilution. (I) hydrophilic-hydrophilic interactions between the hydrophilic (AOH, AC@O, and AOA) polar sites of the polyhydroxy solute and L-ascorbic acid molecules, which give an exothermic contribution to the value of enthalpy of dilution; (II) hydrophobic-hydrophobic interactions between the hydrophobic (R@CH, CH2, CH3) non-polar alkyl groups of solute and the alkyl chain of L-ascorbic acid molecules, which are expected to provide an endothermic contribution to enthalpy of dilution; and (III) hydrophilic-hydrophobic interactions between the polar parts of the solute and the alkyl chain of L-ascorbic acid molecules that also contribute in endothermic manner leading to the partial dehydration of solute molecules. Overall the contribution to DtrDdilH° values from hydrophilic-hydrophilic (type I) interactions is more favourable at low temperatures and it decreases with the rise of temperature. The temperature trend is regular in all cases of studied solutes (except Me a-Glc and 2de-Glc). The contribution to DtrDdilH° values from type (I) interactions increase with increase in mB values in case of Xyl, no significant contribution to DtrDdilH° values in case of Glc but there is decrease in case of 2de-Glc. In Xyol and Mal, contributions from type (I) interactions are more and correspondingly type (II/III) interactions become weaker with increase in the molality, mB of the cosolute. It has been observed that the positive contribution to DtrDdilH° values increase gradually in case of Xyl, Glc and 2de-Glc at (298.15, 308.15, 318.15) K and in Me a-Glc at all temperatures. In Me aGlc, large positive DtrDdilH° values may be due to the fact that methoxy (AOCH3) group introduces a hydrophobic hydration effect in methyl derivatives of Glc. Due to similar reasons, 2deGlc with methylene (ACH2) group has higher DtrDdilH° values than its parent Glc. However, it can be asserted that the positive contribution to DtrDdilH° values may be due to the predominance of partial dehydration of the hydration shell of these polyhydroxy solutes (Xyl, Glc, 2de-Glc and Me a-Glc) over the exothermic effect due to the prevailing release of structured water from the hydration cospheres to the bulk. Xyol has more negative DtrDdilH° values as compared to Xyl, as polyols having linear open-chain structure in the solution are capable of forming more H-bonds with the water

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P.K. Banipal et al. / J. Chem. Thermodynamics 102 (2016) 322–332

Table 4 Viscosity B-Coefficients of polyhydroxy solutes in water and L-ascorbic acid(aq) solutions over the temperature range (288.15–318.15) K and P = 101.3 kPa. 103
B/(m3
mol1) Solute (+)-D-Xylose

Xylitol (+)-D-Galactose

Galactitol (+)-D-Glucose

2-Deoxy-D-glucose (+)-Methyl-a-D-glucopyranoside

(+)-Maltose (anhydrous)

(+)-D-Xylose

Xylitol (+)-D-Galactose

Galactitol (+)-D-Glucose

2-Deoxy-D-glucose (+)-Methyl-a-D-glucopyranoside

(+)-Maltose (anhydrous)

mB = 0.00 T/(K) = 288.15 0.378, 0.370a 0.368b 0.360c 0.371d

0.05

0.15

0.25

0.35

0.422

0.432

0.437

0.442

0.432 0.444d 0.481 0.489a 0.490b 0.488d

0.470

0.463

0.454

0.445

0.522

0.529

0.553

0.574

0.469 0.463d 0.498 0.498a 0.497b 0.494c 0.493d 0.497g

0.500

0.505

0.511

0.495

0.530

0.566

0.576

0.609

0.472 0.453c 0.508 0.496a 0.495c 1.060 1.071g

0.481

0.537

0.555

0.585

0.531

0.555

0.573

0.596

1.112

1.126

1.142

1.170

0.392

0.400

0.404

0.407

0.431

0.427

0.419

0.410

0.473

0.483

0.504

0.527

0.417

0.422

0.430

0.418

0.488

0.520

0.532

0.568

0.435

0.500

0.520

0.555

0.495

0.520

0.541

0.564

1.073

1.088

1.102

1.135

T/(K) = 308.15 0.329, 0.324a 0.327b 0.327c 0.323d 0.374 0.382d 0.419 0.424a 0.425b 0.429d 0.372 0.361d 0.433 0.433a 0.432b 0.427c 0.436d 0.432g 0.412 0.407c 0.452 0.443a 0.443c 1.006 1.001g

mB = 0.00 T/(K) = 298.15 0.341, 0.336a 0.338b 0.346c 0.339d 0.336e 0.347f 0.406 0.416d 0.448 0.455a 0.457b 0.455d 0.416e 0.407 0.398d 0.461 0.461a 0.460b 0.456c 0.458d 0.440e 0.460g 0.435 0.431c 0.472 0.465a 0.465c 1.021 1.033g T/(K) = 318.15 0.317, 0.309a 0.311b 0.311c 0.310d 0.354 0.362d 0.382 0.388a 0.388b 0.384d 0.311 0.305d 0.409 0.409a 0.410b 0.406c 0.412d 0.410g 0.393 0.384c 0.419 0.412a 0.413c 0.967 0.956g

0.05

0.15

0.25

0.35

0.394

0.405

0.409

0.411

0.453

0.449

0.440

0.430

0.494

0.504

0.526

0.547

0.445

0.450

0.456

0.441

0.506

0.536

0.548

0.584

0.451

0.510

0.529

0.565

0.504

0.529

0.549

0.571

1.081

1.094

1.110

1.138

0.385

0.395

0.398

0.401

0.416

0.414

0.407

0.398

0.444

0.453

0.472

0.495

0.362

0.368

0.375

0.367

0.470

0.501

0.515

0.550

0.424

0.488

0.510

0.544

0.471

0.494

0.517

0.539

1.033

1.057

1.070

1.104

Standard uncertainties, u are: ur(m) = u(m)/m = 0.01, u(T) = ± 0.01 K, u(P) = ± 0.5 kPa (Level of confidence is 0.68). Standard deviations in viscosity B-coefficient lie in the range of (0.007–0.030)
103 m3
mol1. a Reference [29]. b Reference [30]. c Reference [31]. d Reference [32]. e Reference [34]. f Reference [35]. g Reference [42].

molecules. Mal, being a disaccharide containing two Glc + Glc subunits and flexible a (1 ? 4) glycosidic bond between these subunits resulting in the negative DtrDdilH° values at low temperatures (288.15 and 298.15) K at all concentrations of

cosolute and at mB  0.25 mol
kg–1 of L-ascorbic acid(aq) at higher temperatures. These observations show that the hydration behavior of polyhydroxy solutes is highly dependent upon stereochemistry and conformation of these molecules. UV spectroscopic

P.K. Banipal et al. / J. Chem. Thermodynamics 102 (2016) 322–332 Table 5 dB/dT coefficients of polyhydroxy solutes in water and L-ascorbic acid(aq) solutions at P = 101.3 kPa. Solute

103
dB/dT/(m3
mol1
K1) mB = 0.00

0.05

0.15

0.25

0.35

(+)-D-Xylose Xylitol (+)-D-Galactose Galactitol (+)-D-Glucose 2-Deoxy-D-glucose (+)-Methyl-a-Dglucopyranoside (+)-Maltose (anhydrous)

0.0020 0.0027 0.0033 0.0051 0.0030 0.0026 0.0029

0.0011 0.0018 0.0026 0.0044 0.0020 0.0019 0.0019

0.0012 0.0017 0.0025 0.0044 0.0021 0.0016 0.0019

0.0012 0.0016 0.0027 0.0043 0.0020 0.0014 0.0018

0.0013 0.0016 0.0026 0.0041 0.0019 0.0013 0.0018

0.0029

0.0025

0.0021

0.0022

0.0020

Standard uncertainties, u are: u(T) = ±0.01 K, u(P) = ±0.5 kPa (Level of confidence is 0.68). The uncertainity in dB/dT values lies in the range of (0.00010.0005) dm3
K1
mol1.

studies [20] also support the view that hydrophilic-hydrophilic interactions occur between polyhydroxy solutes and L-ascorbic acid through H-bonding between their AOH groups. The heat capacity change, DdilCop,2,m was calculated by fitting the following equations to the corresponding limiting enthalpy of dilution data as [23,24]:

Ddil H ¼ A þ XT

ð4Þ

Ddil H ¼ A þ X 1 T þ X 1 T 2

ð5Þ

The temperature coefficients (X, X 1 and X 2) are given in Table S2. The positive values of X and X1 coefficients i.e. DdilCop,2,m values (Table 3) obtained from both the first- and second-order fit suggest overall structural increase in presence of L-ascorbic acid at all the investigated temperatures. The DdilCop,2,m values increase with the molalities of cosolute but decrease with rise of temperature except Me a-Glc. In case of Me a-Glc, the DdilCop,2,m values decrease with mB but their variation with temperature is not regular. The decrease in the DdilCop,2,m values with the rise of temperature may be due to the formation of hydrogen bonds by –OH groups of solutes with water. This hydrogen bond formation disrupts the hydrogenbonded network of the solvent molecules. The solvent structure breaks and overall the equilibrium shifts towards this less structured state of the solvent molecules [25]. These data also support the previous view that hydrophilic-hydrophilic interactions predominate at low temperatures and are strengthened with increase in molality of cosolute but decrease with the rise of temperature. Enthalpic interaction coefficients have been calculated on the basis of the McMillan-Mayer theory of solutions [26,27] that permits the formal separation of the effects due to interactions between solute and cosolute molecules as:

Dtr Ddil H fH2 O ! L-ascorbic acidðaqÞ g ¼ 2hAB mB þ 3hABB m2B

ð6Þ

Enthalpic interaction coefficients provide information regarding the hydration behavior of the solutes and their ability to interact with water or cosolute molecules. The pair (hAB) enthalpic interaction coefficients are negative at lower temperatures and become positive at higher temperatures (Table S3). The negative pair enthalpic coefficients (hAB) indicate the predominance of hydrophilic-hydrophilic interactions that result in more exothermic effects at (288.15 and 298.15) K in cases of Xyl and Mal, whereas in Xyol, Glc and 2de-Glc at 288.15 K only. Negative contribution to hAB values at (288.15 and 298.15) K for Xyl is more than Xyol, but the positive contribution to hAB values for Xyl from dehydration process is smaller as compared to Xyol at (308.15 and 318.15) K. This may be due to the fact that Xyol possess

329

non-planar sickle conformation leading to the interaction accompanied by the H-bonding. In case of hexoses, the negative values of hAB are higher for Glc than 2de-Glc at 288.15 K, but at (298.15–318.15) K, the values of hAB coefficients follow the order: Glc < 2de-Glc < Me a-Glc. The positive hAB values may be due to the replacement of –CHOH group with –CH2OCH3 group which introduce hydrophobic hydration in this derivative, hence manifesting significantly weaker hydration of Me a-Glc derivative in comparison to Glc. The triplet interaction coefficients (hABB) for solutes (except Xyol) are positive at 288.15 K, whereas negative at other temperatures (except Xyl and Me a-Glc). The triplet interaction coefficients consist of the interactions of three molecules i.e. three body interactions along with the contributions made by the interactions of lower orders [28]. As hABB coefficients are more complex, hence their interpretation is difficult. 3.2. Viscosity and viscosity B-coefficients It is clear (Table S4) that viscosity varies in direct proportion to the molality of L-ascorbic acid(aq) but inverse proportion to the temperature. The viscosities of all the solutes in L-ascorbic acid(aq) solutions are higher than solutions in water, which also vary linearly with the concentration of cosolute. The experimental viscosities of polyhydroxy solutes studied in water show good agreement with the literature data [15–17,19,29–51] except in few cases. The present values of g for (+)-D-xylose in water are in good agreement with the literature values [29–35] (Fig. S1-A(i-iv)) except the values reported by Nain et al. [36–37] at (298.15–318.15) K (Fig. S1-A(ii-iv)). The g values for (+)-D-galactose reported by various workers [29–30,32–34,38–40] (Fig. S1-B(i-iv)) are in good agreement with the present g values at 298.15 K only (Fig. S1-B(ii)). The g values reported by Pal et al. [38] (Fig. S1-B(i)) for (+)-D-galactose are lower than the present and the literature values [29–30,32,39] at 288.15 K, but higher at 308.15 K (Fig. S1-B(iii)). The g values reported by Miglori et al. [41] for (0.2921-3.700) mol
kg1 (+)-D-galactose (Fig. S1-B(v)) at (293.15, 283.15, 278.15, 273.15) K are much higher than presently studied range (0.0402-0.1793) mol
kg1 of (+)-D-galactose at (288.15, 298.15, 308.15, 318.15) K. Zhuo et al. [43] reported the viscosities for (+)-D-glucose in water over the concentration range of (0.2000–1.2000) mol
kg1 at (288.15–308.15) K (Fig. S1-C(i-iii)). Nain et al. [44] reported the g values for (0.1423-1.3877) mol
kg1 (+)-D-glucose over the temperature range (298.15–318.15) K (Fig. S1-C(ii-iv)). The g values have also been reported by Miglori et al. [41] for (0.2921-5.5506) mol
kg1 (+)-D-glucose (Fig. S1-C (v)) at (293.15, 283.15, 278.15, 273.15) K. It may be mentioned here that the concentrations of (+)-D-glucose studied by Miglori et al. [41], Zhuo et al. [43] and Nain et al. [44] are much higher than presently studied range (0.0399–0.1797) mol
kg1 of (+)-D-glucose at (288.15, 298.15, 308.15, 318.15) K. Hence, the variation of g values with the increase of concentration or temperature is not much comparable with the present values. Oroian et al. [45] have reported the viscosities for (0.0100–0.1000) mol
kg1 (+)-D-glucose and (+)-maltose in water (Fig. S1-C,D(ii-iv)). Kumar et al. [46] reported the viscosities for (0.0500–0.1000) mol
kg1 of (+)-maltose monohydrate in water at (298.15 and 308.15) K (Fig. S1-D(ii-iii)). The differences in g values for (+)-D-glucose and (+)-maltose from Oroian et al. [45] and Kumar et al. [46] are due to the differences in concentrations of solutes studied presently. For 2-deoxy-D-glucose and (+)-methyl-a-D-glucopyranoside, the g values are in good agreement with those reported earlier [29,31] (Fig. S1-E,F(i-iv)). Fig. S1-G shows that the Zhu et al. [47] and Jiang et al. [48] studied the viscosities for xylitol in water over the concentration range of (0.1000–1.0000) and (0.2002–1.0002) mol
kg1 at T = (293.15–323.15) K. However, it may be mentioned that we have measured the viscosities of (0.0399–0.1801) mol
kg1 xylitol

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P.K. Banipal et al. / J. Chem. Thermodynamics 102 (2016) 322–332

(a) 0.09

Xyl

(b) 0.12

Gal

0.1

0.07

ΔtB·103/m3·mol–1

ΔtB·103/m3·mol–1

0.08 0.06 0.05 0.04 0.03 0.02

0.08 0.06 0.04 0.02

0.01

0

0 0

0.1

0.2

0.3

0

0.4

0.1

0.2

(c) 0.08

Xyol

(d) 0.07

0.06 0.05 0.04 0.03 0.02

0.3

0.4

0.3

0.4

Gaol

0.05 0.04 0.03 0.02 0.01

0.01

0

0 0

0.1

0.2

0.3

0

0.4

(e) 0.16

0.1

0.2

mB/mol·kg–1

mB/mol·kg–1 Glc

(f) 0.16

0.14

2de-Glc

0.14

ΔtB·103/m3·mol–1

ΔtB·103/m3·mol–1

0.4

0.06

ΔtB·103/m3·mol–1

ΔtB·103/m3·mol–1

0.07

0.12 0.1 0.08 0.06 0.04

0.12 0.1 0.08 0.06 0.04

0.02

0.02

0

0 0

0.1

0.2

0.3

0.4

0

mB/mol·kg–1

0.1

0.2

mB/mol·kg–1

Me α-Glc

(g) 0.14

Mal

(h) 0.16 0.14

0.12

ΔtB·103/m3·mol–1

ΔtB·103/m3·mol–1

0.3

mB/mol·kg–1

mB/mol.kg–1

0.1 0.08 0.06 0.04

0.12 0.1 0.08 0.06 0.04

0.02

0.02

0

0 0

0.1

0.2

0.3

0.4

mB/mol·kg–1

0

0.1

0.2

0.3

0.4

mB/mol·kg–1

Fig. 6. Viscosity B-coefficient of transfer (DtrB) versus molalities (mB) of L-ascorbic acid for (a) (+)-D-xylose (b) (+)-D-galactose (c) xylitol (d) galactitol (e) (+)-D-glucose (f) 2deoxy-D-glucose (g) (+)-methyl a-D-glucopyranoside (h) (+)-maltose (anhydrous) at r, 288.15 K; j, 298.15 K; N, 308.15 K; , 318.15 K.

in water over the temperature range (288.15–318.15) K. Bouchard et al. [49] have reported the viscosity of 10% xylitol at 310 K which is lower than the present one. The viscosities reported for galactitol (Fig. S1-H) are in good agreement with our earlier reported values [32]. The present experimental viscosities for (0.0500–0.3500) mol
kg1 L-ascorbic acid in water show good agreement with the literature data [15,17,19] at (288.15–318.15) K (Fig. S2-A(i-iv)). Mazinani et al. [50] reported the viscosities of (0.5337–1.7919)

mol
kg1 L-ascorbic acid which are higher than present g values (Fig. S2-A(ii-iii)). Jiang et al. [16,48,51] have also reported the viscosities of (0.1000–0.4000) mol
kg1 L-ascorbic acid in water over temperature range (293.15–323.15) K (Fig. S2-A(v)) and present g values are higher than reported ones. These differences in viscosities may be due to difference in the concentration and temperature. Jiang et al. [48] have also reported the viscosities for ternary system consisting (0.2000–1.0006) mol
kg1 of xylitol in (0.1000–0.4000) mol
kg1 L-ascorbic acid(aq) over the temperature

P.K. Banipal et al. / J. Chem. Thermodynamics 102 (2016) 322–332

range (293.15–323.15) K. The qualitative comparison with the current studied (0.0398–0.1796) mol
kg1 xylitol in (0.0500–0.3500) mol
kg1 L-ascorbic acid(aq) at T = (288.15–318.15) K shows that their variation with respect to concentration and temperature is comparable with our g present values (Fig. S3). A representative 3-D plot of g versus mA, molality of Glc in mB = 0.05 mol
kg1 L-ascorbic acid(aq) solutions is given in Fig. 5, over the temperature range (288.15–318.15) K. The Jones-Dole equation was fitted to relative viscosities, gr {gr = g/g0, where g is the viscosity of the solution, and g0 is the viscosity of solvent} to evaluate the viscosity B-coefficients as:

gr ¼ 1 þ Bc

ð7Þ

where c is the molarity of the solution, calculated from molality and density data [20]. The viscosity B-coefficients are positive for the systems studied in water and in L-ascorbic acid(aq) solutions (Table 4). The B-coefficients increase with increase in mB values but decrease with rise of temperature. The magnitude of B-values for the studied solutes are larger in L-ascorbic acid(aq) solutions than in water which indicates that the presence of cosolute strengthens the structure of solution at higher concentration. Tyrrell and Kennerley [52] have mentioned that the dB/dT coefficients are better criterion for determining the structure-making or -breaking nature of a solute. The dB/dT coefficients for the studied solutes are negative (Table 5), which suggest that polyhydroxy solutes behave as ‘kosmotropes’ in water as well as in L-ascorbic acid(aq) solutions, as these enhance the strength of the H-bonding network of bulk water. Based on the signs of second-order derivatives (o2V2°/oT2)P, it was concluded that saccharides/derivatives act as structure makers (kosmotropes) whereas, the polyols act as structure breakers (chaotropes) in water and in L-ascorbic acid(aq) solutions [20]. The viscosity B-coefficients of transfer, DtrB were calculated using the equation analogous to Eq. (3). The DtrB values are positive and increase with rise of temperature from 288.15–318.15 K (Fig. 6). DtrB values increase sharply below mB  0.05 mol
kg–1 and then the values level off afterwards to the different extents in different solutes. The DtrB values show level off effect up to mB  0.15 mol
kg–1 and then values remain almost constant from mB  (0.15 to 0.35) mol
kg–1 in case of Xyl (Fig. 6a) whereas in Gal, the values increase sharply beyond mB  0.15 mol
kg–1 (Fig. 6b). However, in case of Xyol, the leveling off effect that originates from 0.05 mol
kg–1 persists up to mB  0.35 mol
kg–1 while from 0.25 to 0.35 mol
kg–1 in case of Gaol (Fig. 6c and d). Similarly, the DtrB values in cases of Glc, 2de-Glc and Mal, show sharp and linear increase but after mB  0.25 mol
kg–1 (Fig. 6e, f and h). The DtrB values increase almost linearly in case of Me a-Glc at all concentrations of cosolute (except below mB  0.05 mol
kg–1) (Fig. 6g). The DtrB values for Glc and its derivatives follow the order: Me aGlc < Glc < 2de-Glc. The DtrB values are lower for polyols than their respective saccharides, which may be due to the reason that polyols have linear open-chain structures and interact more with the water molecules, hence less with cosolute. Among the polyols, overall Gaol has higher values than Xyol, as Gaol with planar zigzag conformation with longer alkyl chain may solvate to lesser extent by the water molecules and interact more with the cosolute molecules than Xyol possesing non-planar sickle conformation. Moreover, the number of –OH groups in Gaol are more than Xyol leading to an increase in H-bonding interactions with cosolute molecules resulting in the net increase in the DtrB values. Similar trends of DtrV2° values have been observed for polyols, Glc and its derivatives in earlier reported volumetric studies [20]. The DtrB values do not increase with the complexity of the solutes and follow the order: Xyl < Gal < Me a-Glc < Glc < Mal < 2de-Glc. Among the solutes, 2de-Glc interacts strongly with the cosolute, which offers greater resistance to the movement of solute molecules resulting in higher DtrB values.

331

The pair (gAB) and triplet (gABB) viscometric interaction coefficients have been calculated using equation analogous to Eq. (6). The pair (gAB) coefficients are positive while the triplet (gABB) coefficients are negative (Table S5) at all temperatures and their magnitudes increase with rise of temperature. The positive contributions of pair coefficients increase linearly, whereas, the negative contributions of triplet coefficients vary non-linearly. The positive values for gAB indicate the presence of hydrophilichydrophilic interactions between solute and cosolute, while negative values for gABB give some indication about the presence of h ydrophobic-hydrophilic/hydrophobic interactions between solutes and L-ascorbic acid. 4. Conclusion In the present work, we have carried out the calorimetric and viscometric studies to explore the interactions of polyhydroxy solutes with L-ascorbic acid in aqueous solutions. The limiting enthalpy of dilution and their corresponding transfer (DtrDdilH°) values indicate the predominance of hydrophilic-hydrophilic interactions at low temperatures. The enthalpy change (q) for Xyol having open chain structure is less exothermic as compared to its parent saccharide; Xyl. The change in heat capacity (DdilCop,2,m) values indicate more structural increase in the L-ascorbic acid(aq) solutions for all the studied polyhydroxy solutes, except for Me a-Glc. The pair enthalpic interaction coefficients (hAB) are indicative of the dominance of hydrophilic-hydrophilic interactions resulting in exothermic effects over endothermic at low temperatures. The dB/ dT coefficients suggest that the studied polyhydroxy solutes act as ‘‘kosmotropes” in water as well as in L-ascorbic acid(aq) solutions. The above results are also in concordance with earlier reported volumetric and UV absorption studies. Acknowledgment Authors are grateful to the University Grants Commission for the financial support under the scheme MRP-MAJOR-CHEM2013-37407, New Delhi, India. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.jct.2016.07.020. References [1] K. Zhuo, G. Liu, Y. Wang, Q. Ren, J. Wang, Fluid Phase Equilib. 258 (2007) 78–82. [2] B. Ernst, G.W. Hart, D. Siney, Carbohydrates in Chemistry and Biology Vol-1, Wiley-Veh, Weinheim, 2000. [3] D.P. Miller, J.J. de Pablo, H.R. Corti, J. Phys. Chem. B 103 (1999) 10243–10249. [4] H.Q. Wang, L.Y. Zhu, X.G. Hu, N. Chen, J. Chem. Thermodyn. 90 (2015) 8–14. [5] K. Zhuo, Y. Chen, W. Wang, J. Wang, J. Chem. Eng. Data 53 (2008) 2022–2028. [6] P.K. Banipal, A.K. Chahal, T.S. Banipal, J. Chem. Thermodyn. 41 (2009) 452–483. [7] M.P. Longinotti, H.R. Corti, J. Sol. Chem. 33 (2004) 1029–1040. [8] M.V.C. Cardoso, L.V.C. Carvalho, E. Sabadini, Carbohydr. Res. 353 (2012) 57–61. [9] K. Faber, Biotransformation in Organic Chemistry, fifth ed., Springer, 2004. pp. 221222. [10] X.M. Qui, Q.F. Lei, W.J. Fang, R.S. Lin, J. Chem. Eng. Data 54 (2009) 1426–1429. [11] P.K. Banipal, K. Kaur, T.S. Banipal, Fluid Phase Equilib. 402 (2015) 113–123. [12] H. Sun, P. Zhao, M. Peng, World J. Microbiol. Biotechnol. 24 (2008) 2613–2618. [13] Y.F. Hu, Z.X. Zhang, Y.H. Zhang, S.S. Fan, D.Q. Liang, J. Chem. Eng. Data 51 (2006) 438–442. [14] M.B. Blodgett, S.P. Ziemer, B.R. Brown, T.L. Neiderhauser, E.M. Woolley, J. Chem. Thermodyn. 39 (2007) 627–644. [15] I. Banik, M.N. Roy, J. Mol. Liq. 169 (2012) 8–14. [16] X. Jiang, C. Zhu, Y. Ma, J. Chem. Thermodyn. 71 (2014) 50–63. [17] S.S. Dhonge, D.W. Deshmukh, L.J. Paliwal, P.N. Dahasahasra, J. Chem. Thermodyn. 67 (2013) 217–226. [18] I.V. Terekhova, O.V. Kulikov, E.S. Titova, Thermochim. Acta 412 (2004) 121– 124.

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JCT 15-900