Elsevier

Thermochimica Acta

Volume 500, Issues 1–2, 10 March 2010, Pages 128-130
Thermochimica Acta

Short communication
Excess molar enthalpies of dibromomethane with acetonitrile, furan and acetophenone at 303.15 K

https://doi.org/10.1016/j.tca.2010.01.005Get rights and content

Abstract

Excess molar enthalpies HE at 303.15 K using a microcalorimeter have been determined for binary liquid mixtures of dibromomethane (DBM) with acetonitrile, furan and acetophenone over the entire composition range. The excess molar enthalpies values are endothermic for DBM + acetonitrile, and +furan but they are exothermic for the system DBM + acetophenone. The observed values are fitted with the Redlich–Kister equation by means of the least squares method. The excess partial molar enthalpies of the components Hm,1E and Hm,2E have also been evaluated with the help of HE values. The results indicate the existence of specific interactions between all these components.

Introduction

As a part of our continuous efforts to obtain thermodynamic quantities on liquid mixtures of organic compounds [1], [2], [3], [4], [5], we report here excess molar enthalpies of dibromomethane (CH2Br2) (DBM) with acetonitrile, furan and acetophenone at 303.15 K. Binary systems of CH2Br2 with acetonitrile, furan and acetophenone are of considerable interest due to specific interactions between these components in the liquid state. This is caused by the presence of two Br and two H atoms in CH2Br2, which can thus act as σ-acceptors towards, and be involved in the hydrogen bond formation with acetonitrile, furan and acetophenone. The latter will act as n-donors. A literature survey revealed that extensive studies on such systems have not been carried out to date. The data obtained for excess molar enthalpies have been interpreted in this paper.

Section snippets

Experimental

Dibromomethane (Fluka) has been purified by fractional distillation, only the middle fraction was used for experiments. Acetonitrile (B.D.H.), furan (A.R.) and acetophenone (A.R.) were dried over freshly activated molecular sieves before use. The chemicals have a minimum purity of 99.0 mol% as determined by GLC. The purities of chemicals used, as determined by GLC for the samples of dibromomethane, acetonitrile, furan and acetophenone are found to be 99.8, 99.8, 99.3 and 99.0 mol%, respectively.

Results and discussions

Excess molar enthalpies, HE, for various systems are summarized in Table 1. The observed values are fitted with the Redlich–Kister equation by means of the least squares method:HE(J mol1)=x1x2i=0mAi(x1x2)iwhere x1 refers to the mole fraction of CH2Br2. The least square parameters, along with the standard deviations, σ are reported in Table 2. The standard deviations, σ, are calculated using equation:σ=(HEHcalcE)2mn1/2where HE is experimental excess enthalpy and HcalcE is calculated

Acknowledgement

Author is extremely grateful to Mr. Ajay Sagar, Managing Director, Osaw Industrial Products Pvt. Ltd., Ambala Cantt, India, for his valuable co-operation and encouragement during this investigation.

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    When a solid and a liquid are contacted a certain amount of heat is generated by the surface and chemical reactions, and this can be determined by means of suitable calorimetric techniques, which leads to the determination of the immersion enthalpy as a characteristic thermodynamic parameter for a specific system (Silvestre-Albero et al., 2001; Stoeckli and Centeno, 2005). If one thinks that the system is formed by the solid and the liquid one can suppose that the immersion enthalpy is due to the contribution of each one of these, as it happens with the thermodynamic partial molar properties in the case of multicomponent solutions (Tripathi, 2010). In this work, from the experimental enthalpies obtained when carbon is activated with solvent mixes, it is possible to calculate the enthalpic contributions that present the activated carbon and water or hexane at the immersion enthalpy of the solid in the liquid; the calculation is made possible by the similarity with the partial molar enthalpies in the solutions.

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