Volumes, Heat Capacities, and Compressibilities of the Mixtures of Acetonitrile with N,N-Dimethylacetamide and Propylene Carbonate

Abstract

The densities of the mixtures of acetonitrile and N,N-dimethylacetamide or propylene carbonate were measured within the whole composition range of the systems at temperatures (308.15 and 318.15) K, while the isobaric heat capacity and speed of sound in these mixtures were measured within the whole composition range at 298.15 K. The results obtained were used to calculate the excess molar volume and isobaric heat capacity and the partial molar volumes and heat capacities of both components of the mixtures as well as the adiabatic (κ S ) and isothermal (κ T ) compressibility and their excess. The internal pressures of the systems were also calculated. The results have been analyzed and discussed.

Volumes, heat capacities, and compressibilities of the mixtures of acetonitrile and 2-methoxyethanol

“…Some properties of 2-ME being the result of its associated molecular structure locate it somewhere in between protic and aprotic solvents. The results of our investigations of (acetonitrile + 2-methoxyethanol) mixtures and particularly the observed similarity of the course of some thermodynamic functions characterizing this system and the functions describing earlier examined mixtures of acetonitrile with aprotic solvents [1,5] makes it possible to express an opinion that 2-methoxyethanol in the mixtures with acetonitrile behaves like an aprotic solvent. Also, when used as a solvent for electrolytes, the (acetonitrile + 2-methoxyethanol) mixtures behave similarly as the mixtures of acetonitrile with aprotic solvents like DMA, PC [5,47], or DMF [48].…”

“…Preliminary results of our studies on the volume functions of some electrolyte solutions in (AN + 2-ME) mixtures suggest that also in this system 2-ME shows the features of aprotic solvent [5]. Thus it appeared proper to perform more complex examinations of (AN + 2-ME) mixtures by means of various test methods in order to verify this opinion and assess to what extent the properties of the system under discussion are similar to or differ from those of the mixtures of acetonitrile with typical aprotic solvents such as propylene carbonate and N,N-dimethylacetamide examined by us earlier [1]. Only few results of experiments concerning the system under discussion are available in the literature and they are fragmentary and insufficient for its characteristics [6,7].…”

“…Moreover, acetonitrile molecules, in contrast to the above-mentioned solvents, are not able to form H-bonds in ''classical'' sense neither as a proton-donor nor as a proton-acceptor. In our previous paper the results of examinations of the mixtures of acetonitrile with N,N-dimethylacetamide (DMA) and propylene carbonate (PC) have been presented [1]. Now we have focused our interest on the mixtures of AN with 2-methoxyethanol (2-ME).…”

Thermochemistry of electrolyte solutions

“…The characteristic shape of the dissolution enthalpy curves observed seems to be unconnected with the rapid change in the mixed solvent structure. The numerous thermodynamic functions characterizing the AN mixtures examined, which are very sensitive to any changes that occur in the system, have their values almost independent of the mixture composition [30][31][32]. The rapid decrease in the enthalpy of solvation (or transfer) due to the addition of cosolvent to the solution can be attributed to the replacement of AN molecules within the solvation shell of electrolyte by stronger solvating molecules of cosolvent.…”

CHAPTER 7. Excess Volumes of Liquid Nonelectrolyte Mixtures

“…Dimethylcarbonate, OC(OCH 3 ) 2 , has a rather small dipole moment 300 (m ¼ 3.04Â10 À30 C m) and low solubility in water, but is miscible with many organic solvents, such as diethyl ether and methanol; it is a widely used non-toxic, biodegradable methylating agent, replacing carcinogenic iodomethane and dimethyl sulfate, as well as a carbonylating agent, replacing highly toxic phosgene. 301 303 while heat capacities C P at constant pressure and speeds of ultrasound were measured at 298.15 K only. From these experimental data, V E , C E P , a P , b S , b T and the internal pressure…”