A study on Volumetric and Viscometric Properties for the Mixtures of DMF and Other Alcohols from Temperatures ranges 303.15K to 323.15K

Md. Helal Uddin*, M. Z. H. Khan*, Md. Shahrul Islam, G.M. Arifuzzaman Khan, Md. Abdullah-Al-Muhit, Jannatul Ferdaus, Md. Abdul Momin, and SK. Shahinur Rahman Department of Materials Science, Faculty of Engineering, Osaka Prefecture University, 1-1 Gakuen-Cho, Naka-Ku, Sakai, Osaka 599-8531, Japan Faculty of Applied Science and Technology, Islamic University, Kushtia-7003, Bangladesh IMRAM, Tohoku University, Sendai, Japan Youngone Central Laboratory, Youngone Hi-Tech Sportswear Ind. Ltd, Dhaka Export Processing Zone, Savar, Dhaka, Bangladesh ABSTRACT


Introduction
The knowledge of chemical and physical properties of solvent systems containing two (or more) components is often required in theoretical studies [1][2][3] and for industrial and chemical processes at a wide range of temperatures [4][5][6]. The intensive properties may include density, viscosity (fluidity) as well as dielectric constant and refractive index. We have undertaken a study of thermochemical properties of four binary systems, in order to extend our knowledge and eventually to generalize or to improve empirical/theoretical correlation with composition.
The interpretation of nonideality is a fascinating area and a large number of contributions were made over the last decade. Solution theory is still far from adequate to account for solution nonidealities in terms of the properties of the constituent molecules. The experimental data on macroscopic properties such as excess molar volumes, excess viscosities, surface tension, and refractive index often provide valuable information for the understanding of the nature of homo and heteromolecular interactions. Alcohol-amide solutions are of practical importance. DMF to some extent is associated by means of dipole-dipole interactions. Significant structural effects are absent due to the lack of hydrogen bonds. Therefore, it acts as an aprotic protophilic solvent of moderately high dielectric constant (= 36.71) of molecules with a large dipole moment (ì=3.8 D) at 298.15 K [7]. Because of its miscibility with almost all common polar and nonpolar solvents [8][9][10][11][12] it is classified as so-called super solvent. A DMF molecule can interact with an alkanol molecule by virtue of better hydrogen bond acceptor ability of its oxygen atom, resulting in structural and packing effects. Volumetric, viscometric and related thermodynamic properties for the mixtures containing DMF were recently reported in the literature [13][14][15][16][17][18][19][20].
In our previous paper [7] described some physical properties of methanol, ethanol and 2-propanol at temperatures from 303.15 K to 323.15 K. Recently M. Kondaiah et.al [21] measured the densities, and viscosities of mixtures of propionic acid with equimolar mixtures of DMF + methanol/ethanol/1-propanol, over the entire composition range of propionic acid and including the pure liquids, have been measured at the temperatures T/K = 303. 15, 313.15, and 323.15. Therefore, to make a correlation in present paper highlights the molar volumes, excess molar volumes, viscosities, excess viscosities, excess enthalpy of activation, excess entropy of activation, and excess free energy of activation data of DMF + 1propanol, + 2-propanol, + butanol, and + 1-pentanol systems over the whole range of compositions at five different temperatures ranges from 303.15 K to 323.15 K.

Experimental
N,N-dimethyl formamide (DMF), 1-propanol, 2-propanol, butanol and pentanol was purchased from Merck, Germany and used without further purification. Binary mixtures were prepared by mass in air tight Stoppard glass bottle. Density was measured by density measurement bottle using an analytical balance (LIBROR EX-180, Shimadzu, Japan) with a readability of 0.0001 g. Care was taken to avoid evaporation and solvent contamination during preparation of mixtures. The mole fraction was accurate up to the fourth place of decimal.
An Ostwald U-tube viscometer A type (Germany) with sufficiently long efflux time was used for viscosity measurements. An electronic digital stopwatch with a readability of ±0.01 s was used for the flow time measurements. At least three repetitions of each data point obtained were reproducible to ±0.05 s and the results were averaged. All measurements were carried out in a thermostatic water bath (TE-8A, Techne, Germany) controlled to ±0.01 K. The purity of the solvents were assessed by comparing their measured density and viscosity data, in which a) viscosity and density of DMF and butanol, b) density of 1-propanol and 2-propanol were in good agreement but c) viscosity of 1-propanol, 2-propanol and 1-pentanol, and d) density of 1-pentanol were not in good agreement with the literature value [22][23][24][25][26][27] as can be seen in Table 1.
Grunberg and Nissan proposed an equation [33] relating the viscosity and strength of interaction as follows (ii) For the DMF + 2-propanol system (Fig. 6), the excess viscosities are positive over the entire range of composition and the maxima occur at 0.4 mole fraction of DMF.
(iii) The excess viscosities of the DMF + butanol system ( Fig. 7) are negative throughout the entire concentration range and the magnitude is comparatively large.
(iv) The excess viscosities of the DMF + pentanol system ( Fig. 8) are also negative throughout the whole concentration range with minima at 0.4 mole fraction of DMF.
Enthalpy of activation, ∆H # and entropy of activation, ∆S # for viscous flow may be obtained from the Erying equation for viscosity as: For each individual mixtures, when ln(ŋVm/hN) is plotted against 1/T, a straight line is expected, from the slope and intercept of which ∆H # and ∆S # can be calculated respectively. The free energy of activation, ∆G # for viscous flow was then obtained using the thermodynamic relation, The excess enthalpy of activation ∆H #E , entropy of activation, ∆S #E , and free energy of activation ∆G #E were calculated by using the following relation, Where, y is the thermodynamic property of the solution. y1 and y2 are the properties of the pure components forming the binary mixtures, x1 and x2 are the respective mole fractions.    (c) Steric hindrance of the molecules.
The negative values of Ε m V may explain as ( Fig. 1-4): (a) Chemical interaction between constituent molecules such as hetero-molecular association through the formation of H-bond, often termed as strong specific interaction. . In addition, physical interactions, such as geometrical fitting of smaller molecules into the voids created by the larger molecules is also favorable for the present systems. On the other hand, alcohol molecules undergo self-and crossassociation because of the presence of hydrogen bonds [19,31].
Mixing of DMF with an alcohol will induce changes in hydrogen bonding (in the alkanol) and dipolar interactions (in the DMF). On addition of DMF to the pure alcohol the self-association will be disrupted partly or fully and new H-bonds between alcohol and DMF will be formed. At the same time, segmental inclusion of DMF into the vacant spaces left in the structural network of alcohol may also occur.
Aso, volume contraction of DMF +1-propanol is expected to be greater than the systems containing other alcohols. However, as the chain length of alcohols increases, the size effect consequently decreases. The negative contribution to Ε m V due to this effect is therefore expected to be in the order: DMF+ 1-propanol >, + 2-propanol >, + butanol >, + 1pentanol.
The analysis of the previous works shows that the negative values of Ε m V decrease with the increase of the chain length of alkanol [7]. The results of our present investigation of DMF + alkanols (C3-C5) binary mixtures were in conformity with the results of these reported investigations. From Figs. 1 to 4, it is seen that the value of negative excess molar volumes increases with the rise of temperature, meaning that (δ Ε m V /δT)p is negative. This may be accounted for in the following manner.
A fundamental difference in the behavior of excess viscosities observed is that the values are found to be positive for DMF +1-propanol, 2-propanol, whereas they are negative for systems consisting of DMF+ butanol, pentanol. Further, the excess viscosities of these systems, regardless of their sign, can be generalized by saying that the magnitude of the values, |ŋ E |, decreases on increase of temperature as observed from Figs. 5 to 8. The positive excess viscosities (as in Fig. 5 and 6) and positive interaction parameters for the DMF + 1-propanol, +2-propanol systems indicate strong interaction. Masegosa et al. [34] reported positive values of interaction parameters corresponding to systems with negative excesses molar volumes. This consistent with our results. Also the negative excess viscosities (as in Figs.7 and 8 Gracia et al. 1991 [35] observed that for two pyrolidone + 1-alkanols, excess free energies were found to be positive in case of methanol and negative with higher alcohols. The negative value of ∆G #E for DMF + butanol and DMF + 1-pentanol show agreement with above [35] observation. The sign of, ∆G #E for a system is regarded to be more reliable criterion as to tell about the strength of interaction. Thus, if ∆G #E is positive the interaction between the components in O c t o b e r 2 4 , 2014 binary system is strong, the strength of interaction, however, depends upon the magnitude of, ∆G #E . If on the other hand, the sign of ∆G #E is negative the interaction between the components molecule is weak or very weak. The positive values of ∆G #E for DMF + 1-propanol, + 2-propanol over the entire range of composition indicating that the interaction of DMF with 1-propanol and with 2-propanol is strong. The positive ∆G #E can be viewed as the increase of the energy barrier that the species in the solution are to surmount in the flow process. The barrier height is increased due to the formation of associated compound through H-bonding between DMF and 1-propanol, and also between DMF and 2-propanol. The negative ∆G #E for DMF + butanol, + 1-pentanol can be viewed as the reduction of the energy barrier that the species in the solution are to surmount in the flow process the barrier height is reduced for the reduction of surface of the activated complex by the segmental inclusion of DMF into polymolecular alcohol aggregates. All the above positive and negative excess free energy results for the four systems are quite compatible with the positive and negative excess viscosity and interaction parameters as discussed above.

Conclusion
Volumetric, viscometric and their related thermodynamic properties for the four binary systems of DMF + 1-propanol, DMF