Elsevier

Fluid Phase Equilibria

Volume 352, 25 August 2013, Pages 22-27
Fluid Phase Equilibria

Effect of solvent on the volumetric behavior of N,N′-salicylidenephenyl diamine (Salophen) Schiff base at different temperatures (288.15–318.15) K

https://doi.org/10.1016/j.fluid.2013.05.001Get rights and content

Highlights

  • Densities of binary mixtures of Salophen + organic solvents have been measured.

  • Using the density data, volumetric properties of mixtures have been calculated.

  • The Vϕ0 values of Salophen Schiff base were compared in different organic solvents.

  • The results showed that the Salophen in these solvents predominantly acts as a structure breaker.

  • The interaction volumes (Vint) of Salophen in different solvents were calculated using scaled particle theory.

Abstract

Densities of binary mixtures containing N,N′-salicylidenephenyl diamine (Salophen) + organic solvents {dimethylsulfoxide (DMSO), N,N-dimethylacetamide (DMA), 1,4-dioxacyclohexane (1,4-dioxane), and oxolane (THF)} have been measured at 10 K intervals from 288.15 K to 318.15 K. Using these data, apparent molar volumes (Vϕ), standard partial molar volumes (Vϕ0), standard partial molar isobaric expansivity (Eϕ0), Hepler's constant (2Vϕ0/T2)p, and isobaric thermal expansion coefficient (α) have been calculated for all the mixtures. The values of interaction volumes (Vint), and cavity volumes (Vcav) have also been estimated using the scaled particle theory [20]. The results show that Salophen in the studied organic solvents predominantly acts as a structure-breaker.

Introduction

Schiff bases, discovered by Hugo Schiff, are a nitrogen analog of an aldehyde or ketone in which the carbonyl group (Cdouble bondO) has been replaced by an imine or azomethine group (CHdouble bondN) [1]. These compounds are often obtained in good yield and high purity through a straightforward synthetic procedure. Many Schiff bases and Schiff base complexes show some interesting properties, such as fluorescence [2], luminescence [3], and photochromic [4]. Schiff bases have other specifications, such as antifungal, antimicrobial, antiviral, antitumor, plant growth regulation, and dying applications [5], [6]. These compounds can be used to produce conducting polymers, optical materials [7], [8], [9], and pH sensors [10]. Among them, N,N′-salicylidenephenyl diamine Schiff bases (Salophen) are being considered as potential catalysts [11] and can be used in chemical reactions.

Generalized usages of Schiff bases and their complexes need an accurate knowledge of their thermodynamic properties when they are mixed with other compounds. Volumetric properties of mixtures can provide valuable information about solute–solvent and solute–solute interactions in solution. Therefore, in this work, the volumetric properties of Salophen Schiff base in some organic solvents, dimethylsulfoxide (DMSO), N,N-dimethylacetamide (DMA), 1,4-dioxacyclohexane (1,4-dioxane), and oxolane (THF), have been investigated. Apparent molar volumes (Vϕ) of Salophen Schiff base were calculated at T = (288.15–318.15) K and used to estimate the standard partial molar volumes (Vϕ0), standard partial molar isobaric expansivity (Eϕ0), Hepler's constant (2Vϕ0/T2)p, and isobaric thermal expansion coefficient (α). Furthermore, the values of the interaction volumes (Vint), and cavity volumes (Vcav) were estimated using scaled particle theory. All of these parameters were used to interpret various solute–solute and solute–solvent interactions occurring between the components in binary mixtures.

Section snippets

Chemicals

Reagents used in this work were salicylaldehyde, benzene-1,2-diamine, DMSO, DMA, 1,4-dioxane, and THF which their sources and purity are tabulated in Table 1. Density (d), viscosity (η), and refractive index (nD) of the solvents along with their literature values at 298.15 K are given in Table 2.

Synthesis of N,N′-salicylidenephenyl diamine (Salophen) Schiff base

A mixture of benzene-1,2-diamine (10 mmol) in 40 mL of ethanol was added dropwise to a vigorously stirred ethanolic mixture (40 mL) of salicylaldehyde (20 mmol). After the addition was complete, the mixture

Results and discussion

Densities (d) of binary mixtures containing Salophen Schiff base + organic solvents (DMSO, DMA, 1,4-dioxane, and THF) and the calculated apparent molar volumes (Vϕ) at different temperatures (288.15–318.15) K are reported in Table 3. The apparent molar volumes (Vϕ) of Salophen Schiff base in the organic solvents were obtained from the densities of the mixtures using the following equation:Vϕ=Md1000(dd0)mdd0where, M is the molar mass of the Salophen Schiff base, m is the molality of the Schiff

Conclusions

Densities of Salophen Schiff base + organic solvent (DMSO, DMA, 1,4-dioxane, and THF) binary mixtures have been measured at T = (288.15–318.15) K. Using these data, the standard partial molar volumes (Vϕ0), standard partial molar isobaric expansivities (Eϕ0), isobaric thermal expansion coefficients (α), and Hepler's constants (2Vϕ0/T2)p of the mixtures at different temperatures have been calculated. The values of interaction volume (Vint), and cavity volume (Vcav) have also been estimated using

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