520 Korean Chem. Eng. Res., 55(4), 520-529 (2017) https://doi.org/10.9713/kcer.2017.55.4.520 PISSN 0304-128X, EISSN 2233-9558 Viscometric Studies of Molecular Interactions in Binary Mixtures of Formamide with Alkanol at 298.15 and 308.15 K Suman Gahlyan, Sweety Verma, Manju Rani* and Sanjeev Maken † Department of Chemistry, Deenbandhu Chhotu Ram University of Science and Technology, Murthal-131 039, India *Department of Chemical Engineering, Deenbandhu Chhotu Ram University of Science and Technology, Murthal-131 039, India (Received 20 February 2017; Received in revised form 27 March 2017; accepted 31 March 2017) Abstract - Viscosity data were measured at 298.15 K and 308.15 K for formamide + 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol or 2-methyl-2-propanol mixtures. For an equimolar mixture, deviation in viscosity follows the sequence: 2-methyl-2-propanol >2-methyl-1-propanol>1-butanol>2-propanol>1-propanol. The viscosity data were further analyzed in terms of graph theory. Free energy of activation was also calculated from experimental viscosity data along with previ- ously reported excess volume data. The deviation in viscosity and free energy of activation were fitted to Redlich-Kister polyno- mial equation. The viscosity data were also correlated by correlations like Grunberg-Nissan, Tamura-Kurata, Hind- McLaughlin-Ubbelohde, and Katti-Chaudhari relation. Various adjustable parameters, G 12 , T 12 , H 12 , and W vis /RT, of var- ious correlations were used to predict viscosity deviation of binary mixtures. Positive value of G 12 indicates strong inter- action in the studied systems. Grunberg-Nissan relation has lowest deviation among the four correlations for formamide + 1-propanol or 2-propanol mixtures; and for mixtures of formamide with 1-butanol or 2-methyl-1-propanol, Tamura- Kurata has lowest deviation. Grunberg-Nissan gives lowest deviation for formamide + 2-methyl-2-propanol mixtures. Key words: Viscosity, Graph theoretical approach, Formamide, Butanol, Propanol, Intermolecular interactions 1. Introduction Viscosity of various binary mixtures was measured extensively to correlate and derive its relation with other physical properties to get significant knowledge about the various types of molecular interac- tions taking place in the binary mixtures. This is very important for the solutions of many engineering problems concerning heat, mass transport and fluid flow [1,2]. Viscosity data on various liquids and liquid mixtures at varying temperature and pressures have been reported from time to time [3-8]. Formamide was selected for this study, as it is the simplest amide that contains a peptide linkage, the fundamental building block of proteins. Formamide molecules are highly polar [9] and are strongly self-associated through extensive three-dimensional network of hydrogen bonds, through its three hydro- gen bond donors (3 H-atoms) and three acceptors (two lone pairs of electrons at oxygen and one on nitrogen atom). Alcohols are self- associated organic compounds through hydrogen bonding of their hydroxyl groups. These are biologically and industrially important amphiphilic materials. Amide-alkanol mixtures have been widely studied as both are bio- logically interesting compounds. The excess and deviation of a ther- modynamic property of their binary mixture as function of composition, temperature and pressure could be a very effective tool to get infor- mation about molecular structure and intermolecular forces in liquid mixtures. Ultrasonic and viscosity measurements of formamide with etha- nol, 1-propanol, 1,2-ethanediol and 1,2-propanediol at temperatures of 293.15 to 318.15 K were performed by Nain [10]. Densities and viscosities of formamide with polar 2-alkanol (C1-C7) were reported by Almasi as a function of composition and temperatures and inter- preted the data in terms of the statistical associating fluid theory and perturbed chain statistical associating fluid theory [2]. Kondaiah et al. measured the volumetric and viscometric properties of propanoic acid in equimolar mixtures of N,N-dimethyl formamide + alkanols [5]. Negative and positive values of various excess and deviation param- eters were attributed to the existence of strong interactions, like dipole-dipole interactions, H-bonding between the carbonyl group of acid molecules and hydroxyl group of alcohol groups. The viscosity of formamide with 2-methoxyethanol and 2-ethoxyethanol was dis- cussed in terms of molecular interactions due to physical, chemical and structural effects between the unlike molecules [8]. Gracia et al. and Gomez Marigliano and Solimo also studied formamide with alkanol (C1-C3) and observed the sigmoid behavior in viscosity deviation versus mole fraction of formamide curves [11,12]. We have reported excess volume, enthalpy and ultrasonic velocity data for formamide + alkanol in our previous publications [13-19]. In the present paper, viscosity data at 298.15 K and 308.15 K for formamide + 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol or 2-methyl- 2-propanol mixtures are reported. The viscosity data were correlated by using various correlations like Grunberg-Nissan, Tamura-Kurata, Hind-McLaughlin-Ubbelohde, Katti-Chaudhari relation. The measured † To whom correspondence should be addressed. E-mail: sanjeevmakin@gmail.com This is an Open-Access article distributed under the terms of the Creative Com- mons Attribution Non-Commercial License (http://creativecommons.org/licenses/by- nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduc- tion in any medium, provided the original work is properly cited.