CHEM. RES. CHINESE UNIVERSITIES 21, 26(2), 39 317 Apparent Molar Volumes and Solvation Coefficients in Ternary-pseudo-binary Mixtures [(Styrene+Ethyl Acetate or enzene)+(n-methyl-2-pyrrolidone+ethyl Acetate or enzene)] HOU Hai-yun 1, PENG San-jun 2, WANG Sheng-ze 1 and GENG Xing-peng 1 1. College of Environmental and Chemical Engineering, Xi an Polytechnic University, Xi an 7148, P. R. China; 2. College of Chemistry and iological Engineering, Changsha University of Science and Technology, Changsha 414, P. R. China Abstract Over the full range of compositions, in the ternary-pseudo-binary mixtures of x[(1-y)c 6 H 5 CH=CH 2 + ych 3 COOC 2 H 5 (or C 6 H 6 )]+(1-x)[(1-y)NMP+yCH 3 COOC 2 H 5 (or C 6 H 6 )], the apparent molar volumes of each pseudo-pure component at different y values were calculated from the density data at 298.15 K and atmospheric pressure. The results show that the four parameters cubic polynomial can correlate the apparent molar volume with the molar fraction well over the full molar fraction range. The limiting partial molar volumes and the molar volumes of each pseudo-pure component were evaluated with different methods. ased on the limiting partial molar volume and molar volume at a certain y value, a new universal coefficient termed as solvation coefficient γ was defined to describe quantitatively the solvation degree of pseudo-pure solute and the interactions of solute-solvent molecules from the macroscopical thermodynamics viewpoint. The results demonstrate the solvation coefficients decrease with the amount of the third component increasing for each pseudo-pure solute, irrespective of the pseudo-pure solvent. Then the solvation degrees of each pseudo-pure component, the specific interactions between the solute molecule and the solvent one were discussed in terms of the solvation coefficient. Keywords Apparent molar volume; Ternary-pseudo-binary mixture; Solvation coefficient Article ID 15-94(21)-2-39-9 1 Introduction A detailed understanding of the solution behavior of non-electrolyte solutes requires information on a variety of chemical and physical parameters. The volumetric properties are very useful in the study of molecular interactions in solution. oth the excess molar volume and the limiting apparent molar volume at infinite dilution which equals the limiting partial molar volume are important thermodynamic volumetric properties and are very helpful to the identification of solvent-solute and solute-solute interactions. Liquid mixtures containing styrene and N-methyl-2-pyrrolidone(NMP) seem to be very interesting from a practical point of view, due to their increased application in organic synthesis. Wang et al. [1] reported the excess molar volume of binary mixtures of styrene with NMP at 298.15 K. A detailed understanding of the effect of the third component, such as ethyl acetate or benzene, on the excess thermodynamic properties and the corresponding behavior of liquid mixtures is thus an important topic for study from both practical and fundamental viewpoints. Peng et al. [2] reported the influences of the third component, ethyl acetate or benzene on the excess molar volumes of binary mixtures of styrene with NMP at 298.15 K. However, the apparent molar volumes, the method to describe the macroscopical interactions of solute-solvent molecules, the quantitative solvation degrees of solutes are still remained unknown. The present work is a further investigation of our study of volumetric properties and solute-solvent molecules interactions of liquid pseudo-binary mixtures [2]. This study builds upon and expands on the present literature. 2 Experimental enzene used in these experiments was purchased from the Third Shanghai Chemicals Factory, China; its molar fraction purity was >.99. Styrene *Corresponding author. E-mail: houhaiyun77@126.com Received February 9, 29; accepted June 12, 29. Supported by the National Natural Science Foundation of China(No.26738) and the Scientific Research Fund of Xi an Polytechnic University of China(No.S74).
31 CHEM. RES. CHINESE UNIVERSITIES Vol.26 was purchased from Tianjin Chemical Factory(China), extra pure with molar fraction >.99. Ethyl acetate and NMP were also purchased from Tianjin Chemicals Factory, extra pure with molar fraction >.99. The method of purification was described elsewhere [3]. All of the chemicals were stored in the dark in brown bottles and protected against atmospheric moisture and CO 2. Prior to the measurement, all the chemicals were stored with 4A molecular sieves added for one week to reduce any trace amounts of water that might be present, and were partially degassed under vacuum. Gas chromatographic studies(using a HP Series II, Model 589 chromatograph with a capillary column type 199 iz-413e and f.i.d., column temperature 4 K, and He flow rate 4. 1 4 cm 3 /s) show no evidence of appreciable impurities. The purchased styrene, containing a stabilizer(hydroquinone), was distilled under reduced pressure and then immediately used for experiments, in order to prevent the possible partial polymerization of styrene. The purity of the liquid was checked by measuring and comparing the density and refractive index with its corresponding literature values [4] as shown in Table 1. The densities of the pure compounds and mixture samples were measured by means of an Anton Parr DMA 45 vibrating-tube densimeter with an estimated accuracy of ±6 1 5 g/cm 3, and were thermostatted at (298.15±.1) K and atmospheric pressure. Table 1 Densities and refractive index values of the pure components at temperature 298.15 K, and comparison with the literature Component This work Ref.[4] ρ/(g.cm 3 ) 25 n D ρ/(g.cm 3 ) 25 n D enzene.87356 1.59.8737 1.511 Styrene.9151 1.5466.9122 1.5463 N-Methyl-2-pyrrolidone 1.2825 1.4677 1.279 1.468 Ethyl acetate.89431 1.3727.89455 1.3724 Apparent molar volumes were calculated from the density measurements. efore each series of measurements, the densimeter was calibrated at atmospheric pressure using dried air and the triply distilled and degassed water with an electrical conductivity of 4.5 1 4 Ω 1 m 1. All measurements were made at temperature constant to better than ±.1 K. The temperature was measured with a standard platinum resistance thermometer(wzp-1, Yunnan Instrument Factory, China), a precision bridge(qj69, Shanghai Electrical Instrument Works, China), and a null detector(acii-ac15/2, Shanghai Electric Meter Works, China). The precision of the temperature was determined with a 1/1 eckmann thermometer. The accuracy and precision in the temperature measurements were better than ±.1 K and ±.1 K, respectively. All the samples were prepared by mass weighted on a balance with a precision of ±5 1 5 g. Attention was paid to the changes in composition of the samples during weighing and partial degassing. To diminish this effect, the samples were weighed, degassed, and stored in vessels designed and recommended by Takenaka et al. [5]. All molar quantities were based on the relative Atomic Mass Table issued by IUPAC in 1986 [6]. 3 Results and Discussion 3.1 Apparent Molar Volume The apparent molar volume of solute, φ V, is defined as [7 1] φ V =(V n A V * A )/n (1) where V denotes the volume of solution, n A and n are the molar amounts of solvent and solute, respectively, and V * A is the molar volume of pure solvent. Eq.(1) can be rearranged to Eq.(2) when the solute concentration is mole fraction x : φ M Β M Α(1 xβ) 1 1 V = + (2) Β ρ xβ ρ ρα where ρ and ρ A denote the densities of solution and solvent respectively, M and M A are respectively the molecular weight, x is the molar fraction of solute. Herein, the molecular weight is the average molecular weight of pseudo-pure component. In fourteen ternary-pseudo-binary mixtures of x[(1-y)c 6 H 5 CH= CH 2 +ych 3 COOC 2 H 5 (or C 6 H 6 )](1)+(1-x)[(1-y)NMP+ ych 3 COOC 2 H 5 (or C 6 H 6 )](2), the compositions are y=.1593,.2648,.3587,.533,.628,.7539, and.8538 for the mixtures containing CH 3 COOC 2 H 5, and y=.1525,.253,.3892,.518,.6493,.7534 and.8549 for the mixtures containing C 6 H 6. In the case of either pseudo-pure component can be considered as solute of the ternary-pseudo-binary mixtures, the apparent molar volumes of each pseudo-pure component were calculated by means of Eq.(2) and the results are listed in Tables 2 and 3. The apparent molar volumes and molar fractions of each pseudo-pure component in the ternary-pseudo-binary mixtures were fitted by the least-squares method for all points to Eq.(3) [11 13], and are shown in Figs.1 and 2.
No.2 HOU Hai-yun et al. 311 Table 2 Molar fractions, densities, apparent molar volumes of pseudo-pure components 1 and 2 in ternary-pseudobinary solutions x[(1-y)c 6 H 5 CH=CH 2 +ych 3 COOC 2 H 5 ](1)+(1-x)[(1-y)NMP+yCH 3 COOC 2 H 5 ](2) y x ρ/(g cm 3 ) /(cm 3 /( cm 3 y x ρ/(g cm 3 ) /(cm 3 /( cm 3.1593. 1.167.3587.8994.91181 18.7797 94.61.485 1.629 19.1851 96.1824.9598.965 18.9498 93.8643.947 1.23 19.3288 96.255 1..9216.1536.99649 19.556 95.8224.533..96666.299.9914 19.6949 95.6299.475.96426 14.4665 96.6999.2752.98458 19.98 95.436.959.96172 14.586 96.59.3234.97971 11.668 95.2357.1421.95924 14.6772 96.4824.3874.9731 11.2835 95.141.1963.95621 14.852 96.3588.4332.96827 11.4422 94.8577.2564.95273 14.9456 96.222.4844.9628 11.6171 94.689.366.94974 15.586 96.163.525.95889 11.7414 94.5571.3635.94623 15.1933 95.9785.5741.9532 11.9248 94.3718.4215.94257 15.3234 95.8443.6356.9462 111.1331 94.1549.4792.93882 15.4547 95.7117.6971.93927 111.344 93.944.5256.93574 15.5588 95.632.7414.93423 111.4948 93.7818.5853.93171 15.6886 95.4562.7985.92766 111.699 93.5789.6389.928 15.873 95.3232.8685.91952 111.939 93.3193.697.92437 15.9178 95.185.9139.91419 112.869 93.1382.7574.91957 16.648 94.9917.9658.983 112.2685 92.944.7917.9176 16.145 94.8842 1..9394.8426.91326 16.2562 94.7176.2648..99717.9156.9765 16.4292 94.4476.568.99276 17.746 96.398.9698.9333 16.5666 94.2313.154.98887 17.8983 96.1615 1..986.1637.9848 18.731 95.9828.628..95393.2171.97956 18.2399 95.824.469.9522 13.1917 96.8626.2637.97554 18.3784 95.6766.154.94957 13.2733 96.7496.3158.9794 18.5375 95.517.1526.94752 13.3524 96.6577.3695.96612 18.6949 95.3486.211.94494 13.453 96.5441.4252.9699 18.8662 95.1776.2621.94252 13.5435 96.448.4764.95621 19.178 95.152.3142.941 13.645 96.3375.5147.95257 19.1339 94.8952.3715.93715 13.754 96.2246.5615.9488 19.2726 94.7434.4387.93368 13.8786 96.99.6125.94312 19.4236 94.5741.4814.9314 13.9624 96.73.6548.93893 19.5531 94.4378.5258.92898 14.485 95.9194.712.9334 19.7182 94.2452.5871.92555 14.1678 95.7979.7554.92882 19.8552 94.858.6442.92227 14.2783 95.6829.8128.9229 11.344 93.895.719.91887 14.393 95.5655.8674.91721 11.235 93.6828.7538.91575 14.4897 95.4541.9145.91222 11.3535 93.586.885.91238 14.5963 95.3372.9684.9644 11.5269 93.2744.8556.9942 14.6884 95.232 1..93.919.9646 14.7791 95.1176.3587..98516.9551.9297 14.8869 95.29.465.9823 16.583 96.4843 1..89997.957.97865 16.6129 96.3495.7539..93459.1519.97468 16.7496 96.1943.478.93338 11.133 97.187.2184.96984 16.9151 96.83.135.93194 11.1693 97.278.2636.96645 17.345 95.8822.1628.9331 11.248 96.9428.3163.96241 17.1732 95.7339.2182.92873 11.3142 96.865.3726.95796 17.337 95.5792.2632.92738 11.3765 96.7949.4267.9536 17.4773 95.4274.3152.92577 11.4456 96.7173.4738.94972 17.668 95.2962.372.92398 11.5252 96.6375.5292.9456 17.767 95.1432.4254.92213 11.63 96.5538.5738.94125 17.8828 95.178.4661.927 11.661 96.4956.6319.93619 18.44 94.8568.5175.91885 11.7351 96.4199.713.935 18.2323 94.6547.5736.91676 11.8164 96.3375.7514.92553 18.371 94.594.6485.91387 11.9232 96.2237.7936.92167 18.4868 94.3871.757.91157 12.65 96.1387.8482.91662 18.637 94.2192.7614.9928 12.851 96.468 To be continued on the next page.
312 CHEM. RES. CHINESE UNIVERSITIES Vol.26 y X ρ/(g cm 3 ).3937.91457 1.859 96.8925 Table 3 Molar fractions, densities, apparent molar volumes of pseudo-pure components 1 and 2 in ternary-pseudobinary solutions x[(1-y)c 6 H 5 CH=CH 2 +yc 6 H 6 ](1)+x[(1-y)C 6 H 5 CH=CH 2 +yc 6 H 6 ](2) y x ρ/(g cm 3 ) /(cm 3 /( cm 3 y x ρ/(g cm 3 ) /(cm 3 /( cm 3.1525. 1.128.3892.2747.95764 13.1 92.2839.457 1.857 17.6218 94.5385.3284.95351 13.2558 92.126.924 1.413 17.7987 94.368.3843.9497 13.4234 91.9525.1596.99758 18.31 94.15.4353.94492 13.5742 91.7974.216.99245 18.2197 93.934.4921.9417 13.7451 91.6265.2636.98699 18.4177 93.6978.5427.93585 13.8951 91.4717.322.9811 18.6334 93.4789.5973.9317 14.65 91.385.3782.97475 18.8517 93.2523.6512.92627 14.228 91.1424.4249.9696 19.36 93.71.719.92166 14.3733 9.9885.4715.96437 19.217 92.8911.7531.91694 14.5251 9.8256.5366.95694 19.464 92.6376.888.91171 14.6917 9.6477.5912.9559 19.6712 92.426.8582.97 14.8395 9.4829.6547.9439 19.9156 92.1783.9194.915 15.26 9.289.7124.93618 11.1367 91.9493.9698.8968 15.1795 9.139.7721.92894 11.3651 91.77 1..8936.8241.92255 11.5659 91.4974.518..95972.8685.9174 11.7382 91.3179.454.95738 99.8817 92.1814.919.91288 11.8662 91.1635.162.9545 1.869 92.267.9558.968 111.78 9.9459.1672.9553 1.2686 91.8742 1..946.2234.94714 1.4284 91.7355.253..99794.2785.94367 1.5873 91.636.451.99429 15.534 93.975.3247.9469 1.795 91.491.112.98963 15.6698 93.7111.3715.9376 1.8292 91.3761.1574.98479 15.8634 93.5154.4374.93312 1.9959 91.2141.2151.97967 16.588 93.3133.484.92988 11.195 91.962.2755.97414 16.267 93.12.5314.92651 11.2254 9.976.3284.96917 16.4478 92.9156.6314.9192 11.4651 9.711.3828.96393 16.636 92.7245.6951.91438 11.6197 9.5362.4176.9653 16.7528 92.5993.7454.915 11.749 9.3894.478.95521 16.9394 92.413.7921.9682 11.8558 9.2513.5234.94987 17.1189 92.2233.8526.9196 12.57 9.56.5745.94458 17.2954 92.396.956.89758 12.1427 89.8921.6312.93861 17.4913 91.8334.9533.89356 12.2679 89.7314.6862.93271 17.6836 91.6348 1..88954.7414.92671 17.8748 91.4278.6493..9373.7928.9213 18.556 91.2376.512.9354 96.79 91.992.8518.91443 18.2624 91.76.112.9336 96.7877 9.9739.9172.9698 18.4964 9.767.1684.9377 96.8916 9.8575.9639.9161 18.6623 9.5486.2151.9288 96.9763 9.7593 1..8974.2785.92599 97.116 9.6271.3892..97683.3214.9242 97.1841 9.536.51.9735 12.57 92.9579.3722.92158 97.296 9.4316.1112.96945 12.643 92.7779.4241.9192 97.3937 9.3212.1684.96545 12.7992 92.66.4841.91592 97.523 9.1988.2211.96165 12.942 92.4452.5315.91341 97.6159 9.978 To be continued on the next page. /(cm 3 /( cm 3 y x ρ/(g cm 3 ) /(cm 3 /( cm 3.7539.8274.9647 12.182 95.9362.8538.4487.91335 1.1391 96.8257.8846.9396 12.2628 95.8282.4966.91222 1.1914 96.771.9542.978 12.3679 95.74.5471.9111 1.241 96.763 1..89862.5915.9989 1.2887 96.652.8538..92181.6512.9834 1.358 96.5727.539.9294 99.8292 97.2739.7154.9658 1.4215 96.4893.149.921 99.8484 97.225.7821.947 1.4912 96.3812.1631.9191 99.8845 97.1571.8384.932 1.5547 96.2896.228.9186 99.9264 97.92.8946.9128 1.6189 96.1752.2865.9168 99.9834 97.17.9542.89932 1.6933 96.493.3476.91557 1.364 96.944 1..89773
No.2 HOU Hai-yun et al. 313 y x ρ/(g cm 3 ) /(cm 3 /(cm 3 y x ρ/(g cm 3 ) /(cm 3 /( cm 3.6493.641.9942 97.7647 89.9442.7534.8146.89117 95.5552 88.976.6524.9667 97.865 89.8433.8542.88924 95.627 88.8877.7151.93 97.9946 89.717.922.88682 95.737 88.7889.7621.919 98.897 89.635.9536.88414 95.7955 88.751.8145.89698 98.1965 89.484 1..88167.8656.89376 98.331 89.3637.8549..965.919.89143 98.3789 89.2747.445.9532 92.47 89.527.9551.88794 98.4914 89.1382.923.9449 92.561 89.4592 1..88492.1554.9332 92.1254 89.3764.7534..92148.215.9242 92.1723 89.3137.462.9225 94.3523 9.3185.2665.915 92.255 89.2262.912.919 94.4138 9.2454.3112.95 92.351 89.1655.1454.91745 94.4721 9.1532.3612.89888 92.3655 89.961.254.91562 94.566 9.519.4187.89743 92.4436 89.25.2514.91415 94.6293 89.9731.584.8952 92.5622 88.96.318.91247 94.762 89.886.5474.89392 92.6123 88.8466.3552.916 94.7921 89.7944.5614.89352 92.6297 88.8263.4114.9854 94.8839 89.6979.5942.89254 92.6749 88.7844.4586.9675 94.9592 89.6144.6584.8958 92.7582 88.6941.512.956 95.318 89.5425.745.88911 92.8188 88.6293.5682.9232 95.142 89.4244.7412.88791 92.8664 88.5749.611.992 95.1979 89.3681.7937.88613 92.936 88.4988.6532.89866 95.2836 89.2736.8473.88426 93.59 88.494.7154.89585 95.3888 89.1636.911.88196 93.912 88.3111.7626.89367 95.4658 89.697.9633.87994 93.164 88.233.641.9942 97.7647 89.9442 1..87849 Fig.1 Plots of apparent molar volume against molar fraction for ternary-pseudo-binary mixtures x[(1-y)c 6 H 5 CH=CH 2 + ych 3 COOC 2 H 5 ](1)+(1-x)[(1-y)NMP+yCH 3 COOC 2 H 5 ](2) at 298.15 K and atmospheric pressure (A) -x 1 ; () -x 2. y:.8538;.7539;.628;.533;.3587;.2648;.1593. Fig.2 Plots of apparent molar volume against molar fraction for ternary-pseudo-binary mixtures x[(1-y)c 6 H 5 CH=CH 2 + yc 6 H 6 ](1)+(1-x)[(1-y)NMP+yC 6 H 6 ](2) at 298.15 K and atmospheric pressure (A) -x 1 ; () -x 2. y:.8538;.7539;.628;.533;.3587;.2648;.1593. In each figure, the solid lines represent the values calculated from the smoothing Eq.(3), the points represent the experimental values from Eq.(2). φ φ 2 3 V = V + x + x + x + (3) 1 2 3 In each case, the optimum value of coefficient is ascertained from an examination of the variation of the standard deviation σ:
314 CHEM. RES. CHINESE UNIVERSITIES Vol.26 φ φ 2 ( V V ) 1 / 2 n σ =, exp., i, cal., i ( n j) (4) i= 1 where, φ V, exp. is from Eq.(2), φ V, cal. from Eq.(3); n, j are the numbers of experimental data and parameters, respectively. The fit results of Eq.(3) for each quasi-pure component are listed in Table 4, where the correlation coefficients φ V, 1, 2, 3 and the corresponding standard deviation σ can be obtained. These coefficients are all constants at a definite y va- lue and temperature 298.15 K, in which the constant φ V represents the apparent molar volume of a pseudo-pure solute at infinite dilution that equals the limiting partial molar volume of the solute, which can provide some information on solvent-solute interactions and solvation of solute. 1, 2, 3 are empirical parameters that depend on solvent, solute, temperature and the amount of the third component. Table 4 Least-squares parameters φ V, 1, 2, 3 and standard deviations σ of Eq.(3) for pseudo-pure components 1 and 2 at 298.15 K and atmospheric pressure * Component y φ V /(cm 3 1 /(cm 3 I 2 /(cm 3 3 /(cm 3 σ/(cm 3 Component y φ V /(cm 3 1 /(cm 3 II 2 /(cm 3 3 /(cm 3 σ/(cm 3 1.1593 19.329 3.418.631.2992.36 1.1525 17.4613 3.5214.55.2459.34.2648 17.5661 3.1763.4197.352.18.253 15.3442 3.2933.215.653.45.3587 16.3931 2.258.8247.4264.5.3892 12.368 2.56.856.4118.54.533 14.3479 2.433.415.254.62.518 99.736 3.4825 1.7561.94.22.628 13.1131 1.4843.7481.3816.42.6493 96.678 1.5889.7837.475.5.7539 11.716.9866.7643.3998.61.7534 94.2939 1.1793.7459.3544.41.8538 99.796.435.8991.3953.49.8549 91.962.9729.5327.2588.27 2.1593 92.896 3.9292.7755.3958.36 2.1525 9.7565 4.32.661.3249.38.2648 93.1559 4.139 1.4385.6443.48.253 9.4154 4.192.8322.3786.62.3587 93.7382 3.2681.7812.3975.29.3892 9.65 3.468.734.3772.37.533 94.1117 4.2416 2.9894 1.4687.55.518 89.5638 3.696 1.6264.753.23.628 94.8942 2.416.6858.3378.32.6493 89.289 2.5673.782.414.32.7539 95.6171 1.9477.7612.3832.32.7534 88.615 2.726.4652.197.46.8538 95.9566 2.2475 1.6281.7745.59.8549 88.1459 1.8273.781.3981.43 * I: x[(1-y)c 6 H 5 CH=CH 2 +ych 3 COOC 2 H 5 ](1)+(1-x)[(1-y)NMP+yCH 3 COOC 2 H 5 ](2); II: x[(1-y)c 6 H 5 CH=CH 2 +yc 6 H 6 ](1)+(1-x)[(1-y)NMP+ yc 6 H 6 ](2). 3.2 Limiting Partial Molar Volume, Molar Volume, Solvation Coefficient and Interactions of Solute-solvent The apparent molar volume of a solute at infinite dilution is equal to the limiting partial molar volume of the solute [8,14], and that in an infinite concentrated solution is equal to the molar volume. Therefore, Table 5 Eq.(5) can be obtained from Eq.(3) by setting x =: φ V = V (5) Similarly, substituting x =1 into Eq.(3) leads to: φ V = V + 1 + 2 + 3 +L (6) So, the limiting partial molar volumes and molar volumes can be evaluated from Eqs.(5) and(6), the results are listed in Table 5. Molar volumes, limiting partial molar volumes and solvation coefficients of pseudo-pure components 1 and 2 at infinite dilution, 298.15 K and atmospheric pressure V * 1 /(cm 3 V * 2 /(cm 3 1 /(cm 3 2 /(cm 3 δ Composition y 1 /(cm 3 δ 2 /(cm 3 mol 1 1 3 γ ) 1 1 3 γ a b a b c d c d 2 I.1593 112.38 112.39 96.36 96.35 19.3 19.4 92.81 92.79 3.35 3.55 29.8 36.8.2648 11.63 11.63 96.5 96.48 17.57 17.57 93.16 93.15 3.6 3.34 27.7 34.6.3587 19.5 19.6 96.63 96.61 16.39 16.39 93.74 93.71 2.66 2.89 24.4 29.9.533 16.63 16.65 96.84 96.81 14.35 14.35 94.11 94.9 2.28 2.73 21.4 28.2.628 14.96 14.98 96.97 96.95 13.11 13.1 94.89 94.89 1.85 2.8 17.6 21.4.7539 12.42 12.44 97.19 97.17 11.7 11.6 95.62 95.61 1.35 1.57 13.2 16.2.8538 1.73 1.54 97.35 97.33 99.8 99.8 95.96 95.94.93 1.39 9.2 14.3 II.1525 111.24 111.25 94.72 94.71 17.46 17.48 9.76 9.74 3.78 3.96 34. 41.8.253 18.79 18.79 94.7 94.6 15.34 15.34 9.42 9.43 3.45 3.65 31.7 38.8.3892 15.26 15.27 93.12 93.11 12.36 12.37 9.1 89.98 2.9 3.11 27.6 33.4.518 12.4 12.39 92.3 92.3 99.73 99.61 89.56 89.43 2.67 2.74 26.1 29.7.6493 98.57 98.59 91.22 91.2 96.61 96.62 89.3 89.2 1.96 2.19 19.9 24..7534 95.86 95.88 9.4 9.39 94.29 94.3 88.6 88.57 1.57 1.8 16.4 19.9.8549 93.21 93.22 89.59 89.58 91.96 91.98 88.15 88.13 1.25 1.44 13.4 16.1 a. from eq.(6); b. from eq.(9); c. from eq.(5); d. from eqs.(7) and (8). I: x[(1-y)c 6 H 5 CH=CH 2 +ych 3 COOC 2 H 5 ](1)+(1-x)[(1-y)NMP+yCH 3 COOC 2 H 5 ](2); II: x[(1-y)c 6 H 5 CH=CH 2 +yc 6 H 6 ](1)+(1-x)[(1-y)NMP+ yc 6 H 6 ](2).
No.2 HOU Hai-yun et al. 315 On the other hand, it is also known that the limiting partial molar volume could be derived from Eqs.(7) and(8), though which does not always provide the best representation of the limiting partial molar volume at infinite dilution. There, the subscripts 1 and 2 denote the pseudo-pure components(styrene+ ethyl acetate, or benzene) and (NMP+ ethyl acetate, or benzene). 1 2 V, V denote the molar volumes of pseudo-pure components 1 and 2, respectively, which can be calculated from the density data via Eq.(9). A i denotes the Redlich-Kister equation coefficients, which have been all shown in our previous work [2]. The derived results are listed in Table 5. V j 1 A i i= j * i 2 = V2 + A i 1) i= * V 1 = V + (7) ( (8) Moreover, the values of molar volumes can also be calculated via Eq.(9) from density data listed in Tables 2 and 3. V = M / ρ (9) The results in Table 5 show that the values of the limiting partial molar volumes evaluated via Eqs.(5), (7) and (8) are consistent with each other and almost within.3 cm 3 /mol, the molar volumes evaluated via Eqs.(6) and (9) are also consistent with each other and almost within.2 cm 3 /mol for each pseudo-pure component. All those demonstrate that the apparent molar volumes and the mole fractions of each pseudo-pure component in the investigated ternarypseudo-binary mixtures can be correlated well by the four parameters cubic polynomial Eq. (3) over the entire concentration range, where the limiting partial molar volumes and the molar volumes of either pseudo-pure component in the either ternary-pseudobinary mixture can be derived successfully. It is well known that at infinite dilution, only solute-solvent, solvent-solvent interactions can exist, and solute-solute interactions can be negligible. Therefore, the variable V can provide some evidence about the effect of the solvent on the structure of the solute. The variable V may be assumed to result from the sum of two contributions: the intrinsic volume of the non-solvated solute molecules and a term which takes into account the volume changes of solute caused by the solvent molecules during the solvation process [7,15]. In order to estimate the strength of solute-solvent interaction at dilution, the influence of the third component on the interaction, and the solvation degree of solute from the macroscopical thermodynamics viewpoint, the solvation coefficient γ, at a definite y value and temperature, is defined as Eq.(1), V V NsM / ρ Ns γ = = = (1) V NAM / ρ NA where the numerator, the variable( V V ) presents the changed volume of pseudo-pure solute in solution via the solvation process; N A and N s are, respectively, the Avogadro constant and the pseudo-pure solute molecules number corresponding to the changed solute volume during the solvation process; M, ρ are, respectively, the molecular weight and density of pseudo-pure solute. At a definite y value, for a definite pseudo-pure solute, the larger the changed volume of solute during the solvation process, the bigger the value of the numerator of Eq.(1), the more the molecules of pseudo-pure solute interacted with the pseudo-pure solvent molecules during the solvation process, and the stronger the solvation process of the solute. In other words, the values of the variable[( V V ), numerator in Eq.(1)], can be used to compare the interactions between the solute molecule and the solvent one as well as the solvation degrees of the solute interacted with different solvents at a definite y value and temperature. However, on the other hand, the variable, ( V V ), shows its weakness to present the solvation degree when the amount of the third component and temperature changes are considered, for the variable N s may be influenced by the amount of the third component and the temperature as well as variable ρ. The equivalent of the macroscopical thermodynamic variable ( V V ) can simply be considered as (N s M /ρ ). It is difficult to distinguish the contributions of the solvated molecules from the thermal agitation s to the macroscopical thermodynamic variable. So, the variable V * is introduced as the denominator of Eq.(1), which deducts the influences of the amounts of the third component and the thermal agitation on ρ, namely, which deducts the influences of the amounts of the third component and the thermal agitation on the volumes of non-solvated pseudo-pure solute molecules and solvated pseudo-pure solute mo-
316 CHEM. RES. CHINESE UNIVERSITIES Vol.26 lecules. Then, only the number of the solvated solute molecules, N s, the inner essential variable is reserved to couple with the Avogadro constant to present the solvation degree at any amounts of the third component and temperature. Thirdly, how the solvation degrees of different solutes expressed for a definite solvent? Obviously, the variable, ( V V ) shows its insufficiency, too. ecause both the number of the solvated solute molecules N s and the molecular weight of solute M can influence the value of the variable at a definite amount of the third component and temperature. When the variable V * is introduced as the denominator in Eq.(1), the influence from molecular weight of solute M is deducted, too. Now a conclusion can be tentatively drawn out that the solvation coefficient γ in Eq.(1) is a universal coefficient to describe the solute-solvent molecule interactions and the solvation degrees of solutes whether the amount of the third component, the temperature or the different solute-solvent pairs are considered. Contrast to the total interactions of solutesolute molecules, for γ>, the total interactions of solute-solvent molecules are attractive, for γ=, the total interactions of solute-solvent molecules are equal to that of solute-solute ones, for γ<, the total interactions of solvent-solvent molecules are repulsive. From the view mentioned above, the solvation coefficients of each pseudo-pure component in these ternary-pseudo-binary mixtures at each amount of the third component, ethyl acetate or benzene, at temperature 298.15 K, are obtained and listed in Table 5. The results show that the values of γ decrease steadily and slightly with the amount of the third component increasing for each pseudo-pure component, which demonstrates that less and less pseudo-pure solute molecules are solvated, the relative attractive interactions of solute-solvent molecules are weakened more and more with the amount of the third component increasing in the two ternary-pseudo-binary mixtures, whether either of pseudo-pure components 1 and 2 is solute, which is consistent with the result from excess volumes [2]. The amount of the third component controls the interactions of pseudo-pure components 1 and 2 and the solvation coefficients of each pseudo-pure component. The solvation coefficient of pseudo-pure component 1 decreases from 29.77 1 3 to 9.32 1 3, and that of pseudo-pure component 2 decreases from 36.84 1 3 to 14.32 1 3 with y value increasing from.1593 to.8538 for the mixtures containing CH 3 COOC 2 H 5. For the mixtures containing C 6 H 6, with y value increasing from.1525 to.8549, the solvation coefficient of pseudo-pure component 1 decreases from 33.98 1 3 to 13.38 1 3, and that of pseudo-pure component 2 decreases from 41.87 1 3 to 16.12 1 3. As we know, the molecules of styrene and NMP are polar. There is a strong interaction between styrene and NMP when they are mixed, the volume contracts, which has been proved from the study of excess volumes of mixtures [1,2]. In view of the solvation coefficient, the addition of the third component, CH 3 COOC 2 H 5 or C 6 H 6, which is a weak polar or a non-polar molecule, can destroy the strong attractive interactions between styrene molecules and NMP ones of the binary mixture, leading to the decrease of the solvation coefficient. However, the ability of CH 3 COOC 2 H 5 is stronger than that of C 6 H 6, so the solvation coefficients of quasi-pure components 1 and 2, containing CH 3 COOC 2 H 5, are both smaller than those containing C 6 H 6 at a certain y value, which is shown in Fig.3. The reasonable explanations are that benzene is a cyclic molecule, and it can more efficiently stack with styrene and NMP, both also cyclic molecules, than with ethyl acetate, a linear molecule. Simultaneously, though C 6 H 6 is non-polar molecule, the π-electrons of benzene ring form π 6 6 chemical bound. Styrene and NMP molecules are both polar ones with π-electrons, which lead the non-polar C 6 H 6 into an induced-dipolar state easily. The different molecules, styrene, NMP and C 6 H 6 can interact on each other through π π interactions. The Fig.3 Solvation coefficients of pseudo-pure components at different y values in two ternarypseudo-binary mixtures at 298.15 K and atmospheric pressure x[(1-y)c 6 H 5 CH=CH 2 +ych 3 COOC 2 H 5 ](1)+(1-x)[(1-y)NMP+yCH 3 COOC 2 H 5 ](2): pseudo-pure component 1; pseudo-pure component 2; x[(1-y)c 6 H 5 CH=CH 2 +yc 6 H 6 ](1)+(1-x)[(1-y)NMP+yC 6 H 6 ](2): pseudopure component 1; pseudo-pure component 2.
No.2 HOU Hai-yun et al. 317 π-electrons of benzene ring lower the shelter effect of benzene between styrene and NMP molecules in contrast to ethyl acetate as shelter molecules. The last, the component with smaller structure size has the bigger solvation coefficient for a pair of pseudo-pure components in a solution, which can explain the fact that the solvation coefficient of pseudo-pure component 1 is smaller than that of pseudo-pure component 2 at the same y value whether the third component is CH 3 COOC 2 H 5 or C 6 H 6. 4 Conclusions This paper not only provides a set of fundamental thermodynamics data of ternary-pseudo-binary mixtures of x[(1-y)c 6 H 5 CH=CH 2 +ych 3 COOC 2 H 5 (or C 6 H 6 )](1)+(1-x)[(1-y)NMP+yCH 3 COOC 2 H 5 (or C 6 H 6 )] (2) at 298.15 K and atmospheric pressure, but also provides a universal method to describe quantitatively the interactions of solute-solvent molecules and the solvation degree of pseudo-pure solute in the ternary-pseudo-binary mixture from the macroscopic thermodynamic viewpoint, this method is suitable for the investigated mixtures, and assesses the influences of the third component, ethyl acetate or benzene, on the molecular interactions between styrene and NMP further. Three conclusions are thus drawn as follows. First, the apparent molar volumes have been calculated from the density data. The apparent molar volumes and the molar fractions over the entire concentration range can be correlated well by a four parameters cubic polynomial equation, the parameters of the equation for each investigated quasi-pure component are obtained by the least-square fitting method. The limiting partial molar volumes at infinite dilution obtained by two different methods are consistent with each other and almost within.3 cm 3 /mol, the molar volumes are also consistent with each other and almost within.2 cm 3 /mol for each pseudo-pure component, which demonstrates that the four parameters cubic polynomial equation can successfully correlate the apparent molar volumes and the molar fractions over the full molar fraction range. Second, the limiting partial molar volume and the molar volume are used to define a new universal coefficient termed as solvation coefficient to express quantitatively the solvation degrees of pseudo-pure solutes and discuss the specific interactions of solute-solvent molecules in the presence of the third component, ethyl acetate or benzene in the ternary-pseudo-binary mixtures of x[(1-y)c 6 H 5 CH= CH 2 +ych 3 COOC 2 H 5 (or C 6 H 6 )](1)+(1-x)[(1-y)NMP+ ych 3 COOC 2 H 5 (or C 6 H 6 )](2). Third, it is reasonable to presume that the solvation coefficient can be considered as a macroscopical thermodynamics variable to scale the interactions of solute-solvent molecules and the quantitative solvation degrees of solutes in ternary-pseudo-binary or binary mixtures. References [1] Liu X. H., Su Z. X., Wang H. J., et al., J. Chem. Thermodyn., 1996, 28(3), 277 [2] Peng S. J., Hou H. Y., Zhou C. S., et al., J. Solution Chem., 27, 36(8), 981 [3] Riddick J. A., unger W.., Organic Solvents, 4th Ed. Techniques of Chemistry, Vol. II, Wiley, New York, 1986 [4] Weast R. C., Handbook of Chemistry and Physics, 58th Ed. CRC Press Inc., Florida, 1978 [5] Takenaka M., Tanaka R., Murakami S., J. Chem. Thermodyn., 198, 12(9), 849 [6] IUPAC Commission on Atomic Weights and Isotopic Abundances 1985, Pure Appl. Chem., 1986, 58, 1677 [7] Tasic D. R., Klofutar C., Monatshefte Für Chemie, 1998, 129(12), 1245 [8] Harned H. S., Owen.., The Physical Chemistry of Electrolyte Solutions., Reinhold, New York, 1954 [9] landamer M. J., Chem. Soc. Rev., 1998, 27, 73 [1] Wawer J., Krakowiak J., Placzek A., et al., J. Mol. Liq., 28, 143(2/3), 95 [11] Liu D. X., Li H. R., Deng D. S., et al., Chin. J. Chem. Eng., 22, 1(4), 454 [12] Hou H. Y., Peng S. J., Wang X. X., et al., Chem. J. Chinese Universities, 29, 3(3), 563 [13] Hou H. Y., Wang X. X., Peng S. J., et al., Chem. J. Chinese Universities, 29, 3(7), 1386 [14] Tasic D. R., Klofutar C., Monatshefte Für Chemie, 23, 134(9), 1185 [15] Wurzburger S., Sartorio R., Guarino G., et al., J. Chem. Soc. Faraday Trans. I, 1988, 84, 2279