- Email: [email protected]
Excess molar volumes of binary mixtures containing vinyl acetate + alkyl acetates at 298.15 K. Anomalous behavior of methyl acetate + vinyl acetate mixtures
FIIIIDPHAS[ [QUIHBRIA ELSEVIER
Fluid Phase Equilibria 137 (1997) 141-148
Excess molar volumes of binary mixtures containing vinyl acetate + alkyl acetates at 298.15 K. Anomalous behavior of methyl acetate + vinyl acetate mixtures C r i s t i n a G o n z f i l e z , J o s e M a R e s a *, J u a n L a n z , J o s e A. M t z . d e I l a r d u y a Departamento de Ingenieria Quimica, UniL'ersidad del Pals Vasco, Apdo. 450. Vitoria, Spain
Received 26 January 1997; accepted 22 March 1997
Abstract Excess molar volumes for binary mixtures containing vinyl acetate + methyl acetate, +ethyl acetate, + propyl acetate, + isopropyl acetate, + butyl acetate, + isobutyl acetate, + pentyl acetate, + isopentyl acetate have been determined from density measurements at 298.15 K using an Anton Paar DMA 58 vibrating tube densitometer. A maximum in densities has been observed for the methyl acetate + vinyl acetate system, where samples with different composition showed the same density. Excess molar volumes increase with an increase of the size of the second acetate. © 1997 Elsevier Science B.V. Keywords: Excess molar volumes; Density; Vinyl acetate; Alkyl acetate
1. Introduction In this work we have investigated the interaction between vinyl acetate and linear and ramificated acetates by measuring the excess molar volumes of mixing. This is a continuation o f our research on the systems involved in the vinyl acetate polymerization in dissolution with methanol [1]. Densities of the mixtures were used to calculate excess molar volumes, and these were fitted to R e d l i c h - K i s t e r polynomials. All measurements were carried out at 298.15 K and atmospheric pressure.
2. Experimental All liquids used were from Fluka, their purities were better than 99.5 mol%, except ethyl acetate that was from Lab-scan, supplied with a purity of 99.8 mol%. T h e y were used without further purification. The purity had been previously checked by gas chromatography.
* Corresponding author. 0378-3812/97/$17.00 © 1997 ElsevierScienceB.V. All rights reserved. PH S0378-3812(97)00083-6
142
C. Gonzdlez et al. / Fluid Phase Equilibria 137 (1997) 141-148
Table 1 Densities and refractive indexes for the studied solvents at 298.15 K Compound
p / g . cm
Methyl acetate Vinyl acetate Ethyl acetate Propyl acetate Isopropyl acetate Butyl acetate Isobutyl acetate Pentyl acetate Isopentyl acetate
3
nD
obsd.
lit%
obsd.
lit a.
0.92705 0.92567 0.89441 0.88210 0.86634 0.87603 0.86626 0.87318 0.86676
0.92790 {).92634 0.89455 1/.88303 0.8702 0.87636 /).8677 0.8719 1/.8664
1.3595 1.3926 1.3705 1.3817 1.3745 1.3920 1.3876 1.4000 1.3985
1.3589 1.3934 1.36978 1.3828 1.3750 1.3918 1.3880 1.400 b 1.3981
~'[2]. b[3]. Mixtures o f the required composition were prepared by measuring the mass with a Salter ER-182A balance, taking precautions to prevent evaporation; the accuracy is within _+ 1 × 10 -4 g. The densities, p, were measured using Anton Paar D M A - 5 8 vibrating-tube densitometer having a resolution of _+ 1 × 10 5 g . c m - < The densitometer was calibrated using water and air, where the density of water was taken at 298.15 K [2], and air density was calculated by the equation: 0.0012930 • P densityt'P = 1 + 0.00367 • t
(1)
where t is temperature in °C and P is pressure in atm. Excess volumes were accurate to _+ 2 x 10 3 cm 3 . t o o l - ~. Temperatures were accurate to _+ 1 X 10 -2 K. Experimental densities and refractive indexes at 298.15 K of the used solvents with the corresponding literature values [2] are listed in Table 1. Refractive indexes were measured with an Abbe type refractometer thermostatized at 298.15 K with an accuracy o f _+ 0.0002.
3. Results and discussion Densities and excess molar volumes of the prepared mixtures are listed in Table 2. The experimental densities p were converted into excess molar volumes V E using the following equation: V E= (xiM 1+x2M2)/p-
[(x,M,/p,) + (x2MJp2) ]
(2)
where xl is the mole fraction o f the more volatile compound and x 2 the mole fraction of the less volatile one, M1 and M 2 the molar masses of the solvents, and p t and P2 the densities of the pure components. The excess volume data were correlated as a function of composition using a three constant R e d l i c h - K i s t e r expansion: VE/cm 3.mol
l = x , x 2 Y'~ ak(x l - x 2 ) k k>_0
(3)
C. Gonz{tlez et al. / Fluid Phase Equilibria 137 (1997) 141-148
143
where a~ are the adjustable parameters obtained by the least square method. Table 3 summarizes the values of the parameters a k together with the standard deviations o- (vE). These coefficients were used to calculate the solid curves in Figs. 1 and 2. In Fig. 1, excess molar volumes of the methyl acetate + vinyl acetate along the mole fraction are plotted. Fig. 2 shows excess molar volumes of vinyl acetate + all the other acetates versus mole fraction of vinyl acetate. From Fig. 2, the binary mixtures containing linear acetates show a regular increase in V E as a function of the number n c with almost symmetric curves with respect to x = 0.5. Structure of vinyl acetate can be described as a hybrid of resonance structure: O
6
CH~-- C ',
" , 6+ N'QO ~
6 CH2
CH
(4)
And the structures of the alkyl acetates can be represented as a resonance structure: Of CH3 - -
(5)
C ', '~"O
~ --
R
In the vinyl acetate + alkyl acetate mixtures, the interaction between molecules is a dipole-dipole one, and the excess volumes depend mainly on the difference in the polarity of the alkyl acetates. The alkyl chain bonded to the partially positive oxygen has an important stabilizer effect, because it scatters the charge by hyperconjugation and inductive effects, which distribute the charge not only carbon atoms but also hydrogen atoms [4]. Those effects and the dispersion degree of the oxygen charge increase with the number of the carbon atoms in the chain and with the branching of it in the series: propyl < isopropyl < butyl < isobutyl < pentyl < isopentyl and in the same order, the intermolecular forces will be lower in the alkyl acetates. In the pentyl acetate or butyl acetate + vinyl acetate mixtures, the interactions between molecules of vinyl acetate are now replaced by lower interactions with alkyl acetates and consequently, excess molar volumes are positive. Excess volumes curves show a behaviour close to ideality for vinyl acetate + propyl acetate and isopropyl acetate. It suggests that charge distribution in these molecules is very similar to the vinyl acetate one. [5] Methyl acetate + vinyl acetate mixtures show negative excess volumes. Methyl acetate can not scatter the positive charge of the oxygen, and has the charges more located and shows strong forces and increase polarity of vinyl acetate. The increase of intermolecular forces causes an negative excess molar volume. The same effect but with lower intensity occurs for the vinyl acetate + ethyl acetate mixtures. The anomalous behavior observed for the methyl acetate + vinyl acetate densities versus mole fraction can be observed in Fig. 3. The plot is not a straight line, a curve with a maximum appears.
C. Gonz61ez et al./ Fluid Phase Equilibria 137 (1997) 141-148
144
Table 2 Densities and excess molar volumes for studied binary systems at 298.15 K x1
p ( g . c m 3)
VE(cm3mol l)
xl
p ( g . c m 3)
VE(cm3mol-i)
-0.014 -0.020 -0.041 -0.052 - 0.059 - 0.073 -0.078 -0.075 - 0.074
0.6212 0.6780 0.7609 0.8025 0.8424 0.8822 0.9237 0.9644 0.9808
0.92725 0.92728 0.92732 0.92729 0.92726 0.92722 0.92718 0.92712 0.92707
- 0.071 -0.065 -0.057 - 0.049 -0.040 -0.031 -0.022 -0.011 -0.004
-0.007 -0.006 -0.013 - 0.024 -0.027 -0.034 - 0.041 -0.051 -0.057
0.5531 0.6069 0.7132 0.7941 0.8450 0.8973 0.9505 0.9758
0.91178 0.91346 0.91675 0.91930 0.92090 0.92252 0.92413 0.92494
-0.055 -0.053 -0.043 - 0.037 - 0.032 -0.023 -0.009 -0.007
0.005 0.008 0.004 0.006 0.002 0.000 0.008 0.006 0.001
0.4986 0.5510 0.6076 0.7023 0.8075 0.8551 0.8979 0.9452 0.9717
0.90143 0.90379 0.90628 0.91057 0.91562 0.91803 0.92022 0.92270 0.92415
0.002 -0.007 - 0.003 0.005 0.009 0.005 0.005 0.004 0.000
-0.004 - 0.002 -0.011 -0.009 -0.003 - 0.005 0.001 0.001 0.001
0.4913 0.5698 0.6126 0.7007 0.7967 0.8521 0.9041 0.9531 0.9770
0.89209 0.89665 0.89921 0.90486 0.91113 0.91499 0.91862 0.92223 0.92401
- 0.011 0.001 0.007 - 0.003 0.004 -0.002 0.002 -0.005 -0.006
0.015 0.009 0.022
0.5968 0.6954 0.8031
0.90090 0.90621 0.91250
Methylacem~ (1)+ vinylacemte(2) 0.0409 0.0633 0.1578 0.2025 0.2979 0.3926 0.4739 0.5380 0.5768
0.92586 0.82595 0.92628 0.92645 0.92665 0.92693 0.92711 0.92717 0.92722
Vinyl acetate (1) + ethyl acetate (2) 0.0223 0.0454 0.0906 0.1569 0.1998 0.2490 0.2984 0.4030 0.4914
0.89513 0.89581 0.89722 0.89930 0.90062 0.90218 0.90375 0.90706 0.90986
Vinyl acetate (1) + propyl acetate (2) 0.0315 0.0501 0.1014 0.1510 0.1992 0.2538 0.3143 0.3997 0.4565
0.88317 0.88381 0.88569 0.88750 0.88934 0.89145 0.98376 0.89723 0.89964
Vinyl acetate (1) + isoropyl acetate (2) 0.0240 0.0504 0.0993 0.1500 0.1937 0.2487 0.3131 0.3962 0.4554
0.86750 0.86874 0.87117 0.87366 0.87582 0.87866 0.88202 0.88657 0.88991
Vinylaceta~ (1)+ b u ~ l a c e m ~ (2) 0.0489 0.0984 0.1464
0.87766 0.87950 0.88121
0.0500 0.045 0.035
C. Gonz(tlez et al. / Fluid Phase Equilibria 137 (1997) 141-148 Table 2 (continued) xt p(g.cm-3)
VE(cm3mo 1- l)
145
Xl
p (g.cm 3)
VE(cm3mol - t)
0.8482 0.9016 0.9482
0.91527 0.91877 0.92198
0.033 0.023 0.011
Vinylacemte(l) 0.1938 0.2515 0.3000 0.4032 0.4994
+ bu~lacemte(2) 0.88299 0.88522 0.88721 0.89163 0.89606
Vinylacetate(2) 0.0229 0.0570 0.1051 0.01471 0.2174 0.2407 0.2966 0.4154 0.4481
+ isobu~lacem~ (2) 0.86722 -0.002 0.86853 0.019 0.87055 0.027 0.87237 0.035 0.87551 0.050 0.87658 0.055 0.87925 0.063 0.88518 0.091 0.88696 0.092
0.5030 0.5681 0.6094 0.7232 0.8048 0.8507 0.8899 0.9541 0.9747
0.88999 0.89385 0.89640 0.90394 0.90973 0.91328 0.91635 0.92173 0.92354
0.098 0.093 0.090 0.070 0.061 0.043 0.035 0.009 - 0.001
Vinylacemte(l) 0.0263 0.0536 0.1060 0.1539 0.2227 0.2495 0.3349 0.3985 0.4552
+ pen~laceta~ (2) 0.87403 0.87492 0.87664 0.87832 0.88082 0.88185 0.88526 0.88802 0.89060
0.003 0.008 0.025 0.033 0.049 0.053 0.069 0.073 0.078
0.4947 0.5489 0.6042 0.7202 0.7966 0.8505 0.8882 0.9523 0.9746
0.89246 0.89515 0.89812 0.90484 0.90986 0.91374 0.91650 0.92169 0.92354
0.085 0.090 0.085 0.082 0.065 0.044 0.039 0.008 0.002
Vinylacem~ (1)+ isopen~lacetate(2) 0.0251 0.86771 -0.005 0.0539 0.86864 0.021 0.1070 0.87061 0.036 0.1454 0.87205 0.053 0.2285 0.87549 0.062 0.2513 0.87641 0.075 0.2873 0.87796 0.086 0.4003 0.88328 0.102 0.4626 0.88649 0.105
0.5093 0.5453 0.5897 0.6915 0.8075 0.8599 0.8987 0.9455 0.9759
0.88902 0.89103 0.89365 0.90016 0.90865 0.91286 0.91614 0.92040 0.92340
0.107 0.112 0.111 0.103 0.073 0.060 0.049 0.026 0.001
0.029 0.038 0.040 0.047 0.051
T h e d e n s i t y o f t h e m i x t u r e s c a n n o t b e u s e d as a c a l i b r a t i o n c u r v e to c a l c u l a t e the c o m p o s i t i o n o f samples of unknown concentration, due samples of different composition show the same density. This b e h a v i o r h a s b e e n o b s e r v e d f o r o t h e r s y s t e m s ( A c e t i c a c i d + w a t e r [6], m e t h a n o l + t o l u e n e [7], p y r i d i n e + w a t e r [8]. T h e p h e n o m e n o n t a k e s p l a c e w i t h c o m p o u n d s o f s i m i l a r d e n s i t i e s . F i g . 4 s h o w s the v o l u m e at the m i n i m u m , o f v i n y l a c e t a t e + l i n e a r a c e t a t e s p l o t t e d a g a i n s t the n u m b e r n c o f c a r b o n a t o m s o f the a c e t a t e . T h e m i x t u r e s s h o w a l i n e a r i n c r e a s e o f e x c e s s v o l u m e as a
146
C. Gonzdlez et al. / Fluid Phase Equilibria 137 (1997) 141-148
Table 3 Adjustable parameters for binary mixtures vinyl acetate + alkyl acetate ao Methyl acetate + vinyl acetate Vinyl acetate + ethyl acetate Vinyl acetate + propyl acetate Vinyl acetate + isopropyl acetate Vinyl acetate + butyl acetate Vinyl acetate + isobutyl acetate Vinyl acetate + pentyl acetate Vinyl acetate + isopentyl acetate
al
- 0.2987 - 0.2164 - 0.0010 0.0022 0.2022 0.3767 0.3409 0.4384
-
a2
0.0075 0.0266 0.0024 0.0301 0.0381 0.0514 0.0877 0.0756
- 0.0015 0.0646 0.0975 - 0.0640 0.0150 - 0.1424 - 0.0394 0.0038
o-3. 103 (cm3.mol
J)
1.6 2.0 3.4 4.3 2.9 4.2 4.6 4.8
0
A +0o5 l / -001
43.02 -0.03
~Eo -004
~'
43.06 0.07
-008 0
02
0.6
0.4
0.8
xI
Fig. 1. Excess molar volumes for methyl acetate ( 1 ) + vinyl acetate (2) versus mole fraction at 298.15 K.
0,12 0.1 0O8 0.06 E
0.04
% o ~
0.02 0 43 0 2
43,04 43.06 0,2
0.4
0.6
0.8
XI
Fig. 2. Excess molar volumes for vinyl acetate ( 1 ) + ethyl acetate (2) ( . ) , + propyl acetate (2) (o), + isopropyl acetate (2) ( zx ), + butyl acetate (2) ( [] ), + isobutyl acetate (2) ( • ), + pentyl acetate (2) ( • ) , + isopentyl acetate (2) ( • ) , versus mole fraction at 298.15 K.
C. Gonzdlez et al. / Fluid Phase Equilibria 137 (1997) 141 148
147
0.928
0.9275
• • 00 • 00000 ~ 0.927
0.9265
0.926
#
0.9255
0.925 0.2
0.4
0.6
0.8
X1
Fig. 3. Densities of the methyl acetate + vinyl acetate mixtures along mole fraction of methyl acetate.
0.1
0.06
"~ E
0.02
/
~, -o.02
47116
./
-0.1
1
2
/ i
i
,
3
4
5
Number of C
atoms
Fig. 4. Excess molar volumes at the minimum value versus number of carbon atoms of the alkyl acetate at 298.15 K.
function of the number of carbons in the alkyl acetate. This relationship has been fitted to the equation: V , ~ , / c m 3. m o l - '
= - 0.126 + 0.0424n c
where V,n~n is the excess m o l a r v o l u m e at the equimolar mole fraction v a l u e .
4. List of symbols ak M nc P T
coefficients in Eq. (3) molar mass number of carbon atoms of the alkyl acetate pressure temperature
(6)
C. Gonzdle'~ et al. / Fluid Phase Equilibria 137 (1997) 141-148
148
VE x~
excess molar volume liquid mole fraction of the more volatile compound
p cr
density standard deviation
Acknowledgements The authors are grateful to the University of the Basque Country for financial support of this work.
References [1] J.M. Resa, B. Moradillo, A. Ruiz, C. Gonzfilez, REcupEration de l'acetate de Vynile n'ayant pas R~agi lors de la REaction de PolymErisation dans le MEthanol, Entropie 202-203 (1997) 1. [2] J. Riddick, W. Bunger, T.K. Sakano, 1986. Organic Solvents: Physical Properties and Methods of Purification. A. Weissberger (Ed.), Wiley-Interscience, New York. [3] TRC-Thermodynamic Tables, 1995. Thermodynamic Research Center, The Texas A&M University System: College Station, TX. [4] H. Pine, J.B. Hendrickson, G.S. Hammond, 1990. Organic Chemistry. McGraw-Hill, New York. [5] H. Ratajczak, W.J. Orville-Thomas, 1980. Molecular Interactions. Wiley-Interscience, New York. [6] K. Noda, Y. Aono, K. Ishida, Kagaku Kogaku Ronbunshu 9 (1983) 237. [7] L.W. Hammond, K.S. Howard, R.A. McAllister, J. Phys. Chem. 62 (1958) 637. [8] J.I. Abe, K. Nakanishi, H. Touhara, J. Chem. Thermodyn. 10 (1978) 483.
Fluid Phase Equilibria 137 (1997) 141-148
Excess molar volumes of binary mixtures containing vinyl acetate + alkyl acetates at 298.15 K. Anomalous behavior of methyl acetate + vinyl acetate mixtures C r i s t i n a G o n z f i l e z , J o s e M a R e s a *, J u a n L a n z , J o s e A. M t z . d e I l a r d u y a Departamento de Ingenieria Quimica, UniL'ersidad del Pals Vasco, Apdo. 450. Vitoria, Spain
Received 26 January 1997; accepted 22 March 1997
Abstract Excess molar volumes for binary mixtures containing vinyl acetate + methyl acetate, +ethyl acetate, + propyl acetate, + isopropyl acetate, + butyl acetate, + isobutyl acetate, + pentyl acetate, + isopentyl acetate have been determined from density measurements at 298.15 K using an Anton Paar DMA 58 vibrating tube densitometer. A maximum in densities has been observed for the methyl acetate + vinyl acetate system, where samples with different composition showed the same density. Excess molar volumes increase with an increase of the size of the second acetate. © 1997 Elsevier Science B.V. Keywords: Excess molar volumes; Density; Vinyl acetate; Alkyl acetate
1. Introduction In this work we have investigated the interaction between vinyl acetate and linear and ramificated acetates by measuring the excess molar volumes of mixing. This is a continuation o f our research on the systems involved in the vinyl acetate polymerization in dissolution with methanol [1]. Densities of the mixtures were used to calculate excess molar volumes, and these were fitted to R e d l i c h - K i s t e r polynomials. All measurements were carried out at 298.15 K and atmospheric pressure.
2. Experimental All liquids used were from Fluka, their purities were better than 99.5 mol%, except ethyl acetate that was from Lab-scan, supplied with a purity of 99.8 mol%. T h e y were used without further purification. The purity had been previously checked by gas chromatography.
* Corresponding author. 0378-3812/97/$17.00 © 1997 ElsevierScienceB.V. All rights reserved. PH S0378-3812(97)00083-6
142
C. Gonzdlez et al. / Fluid Phase Equilibria 137 (1997) 141-148
Table 1 Densities and refractive indexes for the studied solvents at 298.15 K Compound
p / g . cm
Methyl acetate Vinyl acetate Ethyl acetate Propyl acetate Isopropyl acetate Butyl acetate Isobutyl acetate Pentyl acetate Isopentyl acetate
3
nD
obsd.
lit%
obsd.
lit a.
0.92705 0.92567 0.89441 0.88210 0.86634 0.87603 0.86626 0.87318 0.86676
0.92790 {).92634 0.89455 1/.88303 0.8702 0.87636 /).8677 0.8719 1/.8664
1.3595 1.3926 1.3705 1.3817 1.3745 1.3920 1.3876 1.4000 1.3985
1.3589 1.3934 1.36978 1.3828 1.3750 1.3918 1.3880 1.400 b 1.3981
~'[2]. b[3]. Mixtures o f the required composition were prepared by measuring the mass with a Salter ER-182A balance, taking precautions to prevent evaporation; the accuracy is within _+ 1 × 10 -4 g. The densities, p, were measured using Anton Paar D M A - 5 8 vibrating-tube densitometer having a resolution of _+ 1 × 10 5 g . c m - < The densitometer was calibrated using water and air, where the density of water was taken at 298.15 K [2], and air density was calculated by the equation: 0.0012930 • P densityt'P = 1 + 0.00367 • t
(1)
where t is temperature in °C and P is pressure in atm. Excess volumes were accurate to _+ 2 x 10 3 cm 3 . t o o l - ~. Temperatures were accurate to _+ 1 X 10 -2 K. Experimental densities and refractive indexes at 298.15 K of the used solvents with the corresponding literature values [2] are listed in Table 1. Refractive indexes were measured with an Abbe type refractometer thermostatized at 298.15 K with an accuracy o f _+ 0.0002.
3. Results and discussion Densities and excess molar volumes of the prepared mixtures are listed in Table 2. The experimental densities p were converted into excess molar volumes V E using the following equation: V E= (xiM 1+x2M2)/p-
[(x,M,/p,) + (x2MJp2) ]
(2)
where xl is the mole fraction o f the more volatile compound and x 2 the mole fraction of the less volatile one, M1 and M 2 the molar masses of the solvents, and p t and P2 the densities of the pure components. The excess volume data were correlated as a function of composition using a three constant R e d l i c h - K i s t e r expansion: VE/cm 3.mol
l = x , x 2 Y'~ ak(x l - x 2 ) k k>_0
(3)
C. Gonz{tlez et al. / Fluid Phase Equilibria 137 (1997) 141-148
143
where a~ are the adjustable parameters obtained by the least square method. Table 3 summarizes the values of the parameters a k together with the standard deviations o- (vE). These coefficients were used to calculate the solid curves in Figs. 1 and 2. In Fig. 1, excess molar volumes of the methyl acetate + vinyl acetate along the mole fraction are plotted. Fig. 2 shows excess molar volumes of vinyl acetate + all the other acetates versus mole fraction of vinyl acetate. From Fig. 2, the binary mixtures containing linear acetates show a regular increase in V E as a function of the number n c with almost symmetric curves with respect to x = 0.5. Structure of vinyl acetate can be described as a hybrid of resonance structure: O
6
CH~-- C ',
" , 6+ N'QO ~
6 CH2
CH
(4)
And the structures of the alkyl acetates can be represented as a resonance structure: Of CH3 - -
(5)
C ', '~"O
~ --
R
In the vinyl acetate + alkyl acetate mixtures, the interaction between molecules is a dipole-dipole one, and the excess volumes depend mainly on the difference in the polarity of the alkyl acetates. The alkyl chain bonded to the partially positive oxygen has an important stabilizer effect, because it scatters the charge by hyperconjugation and inductive effects, which distribute the charge not only carbon atoms but also hydrogen atoms [4]. Those effects and the dispersion degree of the oxygen charge increase with the number of the carbon atoms in the chain and with the branching of it in the series: propyl < isopropyl < butyl < isobutyl < pentyl < isopentyl and in the same order, the intermolecular forces will be lower in the alkyl acetates. In the pentyl acetate or butyl acetate + vinyl acetate mixtures, the interactions between molecules of vinyl acetate are now replaced by lower interactions with alkyl acetates and consequently, excess molar volumes are positive. Excess volumes curves show a behaviour close to ideality for vinyl acetate + propyl acetate and isopropyl acetate. It suggests that charge distribution in these molecules is very similar to the vinyl acetate one. [5] Methyl acetate + vinyl acetate mixtures show negative excess volumes. Methyl acetate can not scatter the positive charge of the oxygen, and has the charges more located and shows strong forces and increase polarity of vinyl acetate. The increase of intermolecular forces causes an negative excess molar volume. The same effect but with lower intensity occurs for the vinyl acetate + ethyl acetate mixtures. The anomalous behavior observed for the methyl acetate + vinyl acetate densities versus mole fraction can be observed in Fig. 3. The plot is not a straight line, a curve with a maximum appears.
C. Gonz61ez et al./ Fluid Phase Equilibria 137 (1997) 141-148
144
Table 2 Densities and excess molar volumes for studied binary systems at 298.15 K x1
p ( g . c m 3)
VE(cm3mol l)
xl
p ( g . c m 3)
VE(cm3mol-i)
-0.014 -0.020 -0.041 -0.052 - 0.059 - 0.073 -0.078 -0.075 - 0.074
0.6212 0.6780 0.7609 0.8025 0.8424 0.8822 0.9237 0.9644 0.9808
0.92725 0.92728 0.92732 0.92729 0.92726 0.92722 0.92718 0.92712 0.92707
- 0.071 -0.065 -0.057 - 0.049 -0.040 -0.031 -0.022 -0.011 -0.004
-0.007 -0.006 -0.013 - 0.024 -0.027 -0.034 - 0.041 -0.051 -0.057
0.5531 0.6069 0.7132 0.7941 0.8450 0.8973 0.9505 0.9758
0.91178 0.91346 0.91675 0.91930 0.92090 0.92252 0.92413 0.92494
-0.055 -0.053 -0.043 - 0.037 - 0.032 -0.023 -0.009 -0.007
0.005 0.008 0.004 0.006 0.002 0.000 0.008 0.006 0.001
0.4986 0.5510 0.6076 0.7023 0.8075 0.8551 0.8979 0.9452 0.9717
0.90143 0.90379 0.90628 0.91057 0.91562 0.91803 0.92022 0.92270 0.92415
0.002 -0.007 - 0.003 0.005 0.009 0.005 0.005 0.004 0.000
-0.004 - 0.002 -0.011 -0.009 -0.003 - 0.005 0.001 0.001 0.001
0.4913 0.5698 0.6126 0.7007 0.7967 0.8521 0.9041 0.9531 0.9770
0.89209 0.89665 0.89921 0.90486 0.91113 0.91499 0.91862 0.92223 0.92401
- 0.011 0.001 0.007 - 0.003 0.004 -0.002 0.002 -0.005 -0.006
0.015 0.009 0.022
0.5968 0.6954 0.8031
0.90090 0.90621 0.91250
Methylacem~ (1)+ vinylacemte(2) 0.0409 0.0633 0.1578 0.2025 0.2979 0.3926 0.4739 0.5380 0.5768
0.92586 0.82595 0.92628 0.92645 0.92665 0.92693 0.92711 0.92717 0.92722
Vinyl acetate (1) + ethyl acetate (2) 0.0223 0.0454 0.0906 0.1569 0.1998 0.2490 0.2984 0.4030 0.4914
0.89513 0.89581 0.89722 0.89930 0.90062 0.90218 0.90375 0.90706 0.90986
Vinyl acetate (1) + propyl acetate (2) 0.0315 0.0501 0.1014 0.1510 0.1992 0.2538 0.3143 0.3997 0.4565
0.88317 0.88381 0.88569 0.88750 0.88934 0.89145 0.98376 0.89723 0.89964
Vinyl acetate (1) + isoropyl acetate (2) 0.0240 0.0504 0.0993 0.1500 0.1937 0.2487 0.3131 0.3962 0.4554
0.86750 0.86874 0.87117 0.87366 0.87582 0.87866 0.88202 0.88657 0.88991
Vinylaceta~ (1)+ b u ~ l a c e m ~ (2) 0.0489 0.0984 0.1464
0.87766 0.87950 0.88121
0.0500 0.045 0.035
C. Gonz(tlez et al. / Fluid Phase Equilibria 137 (1997) 141-148 Table 2 (continued) xt p(g.cm-3)
VE(cm3mo 1- l)
145
Xl
p (g.cm 3)
VE(cm3mol - t)
0.8482 0.9016 0.9482
0.91527 0.91877 0.92198
0.033 0.023 0.011
Vinylacemte(l) 0.1938 0.2515 0.3000 0.4032 0.4994
+ bu~lacemte(2) 0.88299 0.88522 0.88721 0.89163 0.89606
Vinylacetate(2) 0.0229 0.0570 0.1051 0.01471 0.2174 0.2407 0.2966 0.4154 0.4481
+ isobu~lacem~ (2) 0.86722 -0.002 0.86853 0.019 0.87055 0.027 0.87237 0.035 0.87551 0.050 0.87658 0.055 0.87925 0.063 0.88518 0.091 0.88696 0.092
0.5030 0.5681 0.6094 0.7232 0.8048 0.8507 0.8899 0.9541 0.9747
0.88999 0.89385 0.89640 0.90394 0.90973 0.91328 0.91635 0.92173 0.92354
0.098 0.093 0.090 0.070 0.061 0.043 0.035 0.009 - 0.001
Vinylacemte(l) 0.0263 0.0536 0.1060 0.1539 0.2227 0.2495 0.3349 0.3985 0.4552
+ pen~laceta~ (2) 0.87403 0.87492 0.87664 0.87832 0.88082 0.88185 0.88526 0.88802 0.89060
0.003 0.008 0.025 0.033 0.049 0.053 0.069 0.073 0.078
0.4947 0.5489 0.6042 0.7202 0.7966 0.8505 0.8882 0.9523 0.9746
0.89246 0.89515 0.89812 0.90484 0.90986 0.91374 0.91650 0.92169 0.92354
0.085 0.090 0.085 0.082 0.065 0.044 0.039 0.008 0.002
Vinylacem~ (1)+ isopen~lacetate(2) 0.0251 0.86771 -0.005 0.0539 0.86864 0.021 0.1070 0.87061 0.036 0.1454 0.87205 0.053 0.2285 0.87549 0.062 0.2513 0.87641 0.075 0.2873 0.87796 0.086 0.4003 0.88328 0.102 0.4626 0.88649 0.105
0.5093 0.5453 0.5897 0.6915 0.8075 0.8599 0.8987 0.9455 0.9759
0.88902 0.89103 0.89365 0.90016 0.90865 0.91286 0.91614 0.92040 0.92340
0.107 0.112 0.111 0.103 0.073 0.060 0.049 0.026 0.001
0.029 0.038 0.040 0.047 0.051
T h e d e n s i t y o f t h e m i x t u r e s c a n n o t b e u s e d as a c a l i b r a t i o n c u r v e to c a l c u l a t e the c o m p o s i t i o n o f samples of unknown concentration, due samples of different composition show the same density. This b e h a v i o r h a s b e e n o b s e r v e d f o r o t h e r s y s t e m s ( A c e t i c a c i d + w a t e r [6], m e t h a n o l + t o l u e n e [7], p y r i d i n e + w a t e r [8]. T h e p h e n o m e n o n t a k e s p l a c e w i t h c o m p o u n d s o f s i m i l a r d e n s i t i e s . F i g . 4 s h o w s the v o l u m e at the m i n i m u m , o f v i n y l a c e t a t e + l i n e a r a c e t a t e s p l o t t e d a g a i n s t the n u m b e r n c o f c a r b o n a t o m s o f the a c e t a t e . T h e m i x t u r e s s h o w a l i n e a r i n c r e a s e o f e x c e s s v o l u m e as a
146
C. Gonzdlez et al. / Fluid Phase Equilibria 137 (1997) 141-148
Table 3 Adjustable parameters for binary mixtures vinyl acetate + alkyl acetate ao Methyl acetate + vinyl acetate Vinyl acetate + ethyl acetate Vinyl acetate + propyl acetate Vinyl acetate + isopropyl acetate Vinyl acetate + butyl acetate Vinyl acetate + isobutyl acetate Vinyl acetate + pentyl acetate Vinyl acetate + isopentyl acetate
al
- 0.2987 - 0.2164 - 0.0010 0.0022 0.2022 0.3767 0.3409 0.4384
-
a2
0.0075 0.0266 0.0024 0.0301 0.0381 0.0514 0.0877 0.0756
- 0.0015 0.0646 0.0975 - 0.0640 0.0150 - 0.1424 - 0.0394 0.0038
o-3. 103 (cm3.mol
J)
1.6 2.0 3.4 4.3 2.9 4.2 4.6 4.8
0
A +0o5 l / -001
43.02 -0.03
~Eo -004
~'
43.06 0.07
-008 0
02
0.6
0.4
0.8
xI
Fig. 1. Excess molar volumes for methyl acetate ( 1 ) + vinyl acetate (2) versus mole fraction at 298.15 K.
0,12 0.1 0O8 0.06 E
0.04
% o ~
0.02 0 43 0 2
43,04 43.06 0,2
0.4
0.6
0.8
XI
Fig. 2. Excess molar volumes for vinyl acetate ( 1 ) + ethyl acetate (2) ( . ) , + propyl acetate (2) (o), + isopropyl acetate (2) ( zx ), + butyl acetate (2) ( [] ), + isobutyl acetate (2) ( • ), + pentyl acetate (2) ( • ) , + isopentyl acetate (2) ( • ) , versus mole fraction at 298.15 K.
C. Gonzdlez et al. / Fluid Phase Equilibria 137 (1997) 141 148
147
0.928
0.9275
• • 00 • 00000 ~ 0.927
0.9265
0.926
#
0.9255
0.925 0.2
0.4
0.6
0.8
X1
Fig. 3. Densities of the methyl acetate + vinyl acetate mixtures along mole fraction of methyl acetate.
0.1
0.06
"~ E
0.02
/
~, -o.02
47116
./
-0.1
1
2
/ i
i
,
3
4
5
Number of C
atoms
Fig. 4. Excess molar volumes at the minimum value versus number of carbon atoms of the alkyl acetate at 298.15 K.
function of the number of carbons in the alkyl acetate. This relationship has been fitted to the equation: V , ~ , / c m 3. m o l - '
= - 0.126 + 0.0424n c
where V,n~n is the excess m o l a r v o l u m e at the equimolar mole fraction v a l u e .
4. List of symbols ak M nc P T
coefficients in Eq. (3) molar mass number of carbon atoms of the alkyl acetate pressure temperature
(6)
C. Gonzdle'~ et al. / Fluid Phase Equilibria 137 (1997) 141-148
148
VE x~
excess molar volume liquid mole fraction of the more volatile compound
p cr
density standard deviation
Acknowledgements The authors are grateful to the University of the Basque Country for financial support of this work.
References [1] J.M. Resa, B. Moradillo, A. Ruiz, C. Gonzfilez, REcupEration de l'acetate de Vynile n'ayant pas R~agi lors de la REaction de PolymErisation dans le MEthanol, Entropie 202-203 (1997) 1. [2] J. Riddick, W. Bunger, T.K. Sakano, 1986. Organic Solvents: Physical Properties and Methods of Purification. A. Weissberger (Ed.), Wiley-Interscience, New York. [3] TRC-Thermodynamic Tables, 1995. Thermodynamic Research Center, The Texas A&M University System: College Station, TX. [4] H. Pine, J.B. Hendrickson, G.S. Hammond, 1990. Organic Chemistry. McGraw-Hill, New York. [5] H. Ratajczak, W.J. Orville-Thomas, 1980. Molecular Interactions. Wiley-Interscience, New York. [6] K. Noda, Y. Aono, K. Ishida, Kagaku Kogaku Ronbunshu 9 (1983) 237. [7] L.W. Hammond, K.S. Howard, R.A. McAllister, J. Phys. Chem. 62 (1958) 637. [8] J.I. Abe, K. Nakanishi, H. Touhara, J. Chem. Thermodyn. 10 (1978) 483.