**1. Introduction**

52 Will-be-set-by-IN-TECH

594 Thermodynamics – Interaction Studies – Solids, Liquids and Gases

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A comprehensive investigation of the phase equilibriums and determination of thermodynamic properties of pure substances is a significant object of the chemical thermodynamics. Data on the phase transitions, heat capacities, and saturation vapor pressure over the solid and liquid phases are used in many fields of science and technology, including calculations on the basis of the third law of thermodynamics. Theoretical and practical applications of thermodynamic data require verification of their reliability. The Clapeyron equation combines different properties of coexisting phases: temperature, vapor pressure, volume, enthalpy of the phase transitions, and caloric values*Cp* and*Cv* . Using this equation allows one to verify numerical data for thermodynamic concordance, to reveal unreliable quantities, and to predict failing thermodynamic properties. Mutual concordance and reliability of the calorimetric data on the heat capacity, the saturated vapor pressures, and the properties of phase transition can be verified by comparison of the absolute entropies determined from the experimental data by the third thermodynamic law, ( )( ) *<sup>o</sup> S g <sup>m</sup>* e x p t with those ones calculated by statistical thermodynamics, ( ) *<sup>o</sup> S stat <sup>m</sup>* . A congruence of these values within errors limits justifies their reliability. Critical analyses of the recent data on thermodynamic properties of some organic compounds are published by the National Institute of the Standards and Technology [NIST], USA. Literature data on the vapor pressures and the enthalpies of vaporization for *n*-alkanes C5 – C20 were reviewed and critically analyzed in the reference (Ruzicka & Majer, 1994). Thermodynamic properties of many classes of organic compounds were considered in monograph (Domalski & Hearing, 1993; Poling et al., 2001) that favoured the development of the Benson's calculation method. This chapter deals with reviewing and summarizing the data on the phase equilibriums carried out for some functional organic compounds by the low temperature adiabatic calorimetry, comparative ebulliometry, and vaporization calorimetry in the Luginin's Laboratory of Thermochemistry [LLT] of the Moscow State University [MSU] and other research centres. The numerous data on the heat capacity, the vapor pressure, enthalpies of the phase transitions, and derived thermodynamic functions were obtained for series of freons, cyclic hydrocarbons and fluorocarbons, and derivatives of ferrocene. A sufficient attention was given to the critical analyses of the thermodynamic data, their reliability, and

to interconnections between the properties and some structural parameters of the

Thermodynamics of the Phase Equilibriums of Some Organic Compounds 597

condensed states were calculated on the basis of the heat capacities and the properties of the

Part 4 deals with 1) determination of the ideal gas thermodynamic functions by experimental and theoretical methods, 2) verification of the thermodynamic functions by comparing the absolute entropies calculated on the basis of the third thermodynamic law and by statistical thermodynamics, and 3) the methods of extending the saturated vapor pressure of the "atmospheric" range of pressure to entire region of liquids from the triple to

Parts 5, 6, 7, and 8 present Conclusion, Acknowledgments, References, and Appendix,

The values of the vapor pressure of liquid substances are mostly determined by the static and dynamic (mainly ebulliometric) methods. A comparative ebulliometry is frequently employed due to its simpler technique and suitability for the series of determinations. The greatest number of saturated vapor pressure of organic compounds was obtained by this method in the moderate ("atmospheric") range of pressure 2-3 (, ) *p* <sup>k</sup> <sup>P</sup> <sup>a</sup> 100-150. The highest accurate of vapor pressure is usually attained in this range that makes it possible to obtain reliable derivative values, in particular, the enthalpies of vaporization. Few *pT* data are available in the literature for the entire region of liquid phase because of methodical difficulties and high errors of determination at low (<1 kPa) and high (>200 kPa) pressures.

Fig. 1 presents a schematic view of a setup designed for determinations of the temperature dependence of saturation vapor pressure by comparative ebulliometry (Varouchtchenko &

Fig. 1. The setup for determination of the *pT* parameters: DE, differential ebulliometer; MS, manometer system; (1) mercury-contact manometer; (2) electromagnetic valve; (3) roughing

**2. Temperature dependence of saturated vapor pressure** 

**2.1 Experimental and mathematical processing** 

pump; (4) ballast reservoir; (5) traps

solid-to-solid transitions and fusion.

the critical temperatures.

respectively.

Droujinina, 1995).

compounds. Experimental and calculation methods for determination of the properties rely mostly on the LLT-school.

Freons are halogen derivatives of ethane and propane which possess a unique combination of the useful properties: high volatility, high enthalpy of vaporization, no combustibility, biological inertness, etc. Due to these properties, freons have found a wide application in many areas of science, technology, and medicine (Varushchenko et. al., 2007).

Alkyl derivatives of adamantine, C10H16, , are of an interest due to tendency to form plastic crystals. Bicyclical *cis*- and *trans-* isomers of decaline, C10H18, , and hydrindane, C9H16, , have poor intermolecular interactions and also form plastic crystals. Their perfluoride counterparts exhibit high chemical stability, absolute biological inertness, and capacity for dissolving and transferring large amounts of gases, in particular, oxygen and carbon dioxide. Due to these properties, perfluorocarbons have found wide application in biology and medicine as effective gas-transferring media and artificial blood substitutes. A mixture of perfluorodecaline, C10F18, and perfluoro-N-(4-methylcyclohexyl)piperidine, C12F23N, forms of the "Ftorosan" blood substitute (Russia) (Ries*,* 1991). Bicyclical *cis*- and *trans-* isomers of decaline and hydrindane are of the interest in study of an interconnection between thermodynamic properties and the structure of the compounds when passing from perfluorocarbons to their hydrocarbon counterparts.

Alkyl- and acyl- ferrocene derivatives [FD] are the sandwich-type organometallic compounds discovered in the 50th years of the XX century. Owing to favourable conjunction of the chemical and physical properties, namely low toxicity, high thermal stability, and volatility, some FD has found ever-increasing application in technology (electric materials, regulators of fuel combustion etc.) and medicine (anti-cancer and blood-creating drugs).

This chapter is intended for researchers with an interest in measuring characteristics of the phase transitions and in determination of the equilibrium properties by experimental and theoretical methods. A number of relationships for practical use are represented with illustrative examples and necessary recommendations. The chapter contains main references to the literature used in reviewing and summarizing the numerous data on the properties of some functional organic compounds.

Part 2 deals with the ebulliometric and transpiration methods for determination of the saturation vapor pressure in dependence on the temperature. Design of devices and experimental techniques and mathematical processing of the vapor pressures are given. A modified ebulliometer of an original construction was given for determination of the *pT* parameters in moderate ("atmospheric") pressure region. The enthalpies of vaporization obtained by direct calorimetric method and those ones calculated from the vapor pressure are compared for justifying their reliability. An interconnection between the properties derived from the vapor pressure and some structural parameters of the substances are analyzed.

Part 3 considers the low-temperature adiabatic calorimetry for measuring the heat capacity and studying the properties of the phase transitions. Experimental technique has been presented by modern completely automated adiabatic calorimeter used in LLT. Experimental determination and mathematical processing of the phase transitions were given including an X-ray analysis of crystal structure and the infrared and Raman spectroscopy for interpretation of the processes occurring during the solid-phase transitions. Main thermodynamic functions (changes of the entropy, enthalpy, and Gibb's energy) in

compounds. Experimental and calculation methods for determination of the properties rely

Freons are halogen derivatives of ethane and propane which possess a unique combination of the useful properties: high volatility, high enthalpy of vaporization, no combustibility, biological inertness, etc. Due to these properties, freons have found a wide application in

Alkyl derivatives of adamantine, C10H16, , are of an interest due to tendency to form plastic crystals. Bicyclical *cis*- and *trans-* isomers of decaline, C10H18, , and hydrindane, C9H16, , have poor intermolecular interactions and also form plastic crystals. Their perfluoride counterparts exhibit high chemical stability, absolute biological inertness, and capacity for dissolving and transferring large amounts of gases, in particular, oxygen and carbon dioxide. Due to these properties, perfluorocarbons have found wide application in biology and medicine as effective gas-transferring media and artificial blood substitutes. A mixture of perfluorodecaline, C10F18, and perfluoro-N-(4-methylcyclohexyl)piperidine, C12F23N, forms of the "Ftorosan" blood substitute (Russia) (Ries*,* 1991). Bicyclical *cis*- and *trans-* isomers of decaline and hydrindane are of the interest in study of an interconnection between thermodynamic properties and the structure of the compounds when passing from

Alkyl- and acyl- ferrocene derivatives [FD] are the sandwich-type organometallic compounds discovered in the 50th years of the XX century. Owing to favourable conjunction of the chemical and physical properties, namely low toxicity, high thermal stability, and volatility, some FD has found ever-increasing application in technology (electric materials, regulators of fuel combustion etc.) and medicine (anti-cancer and blood-creating drugs). This chapter is intended for researchers with an interest in measuring characteristics of the phase transitions and in determination of the equilibrium properties by experimental and theoretical methods. A number of relationships for practical use are represented with illustrative examples and necessary recommendations. The chapter contains main references to the literature used in reviewing and summarizing the numerous data on the properties of

Part 2 deals with the ebulliometric and transpiration methods for determination of the saturation vapor pressure in dependence on the temperature. Design of devices and experimental techniques and mathematical processing of the vapor pressures are given. A modified ebulliometer of an original construction was given for determination of the *pT* parameters in moderate ("atmospheric") pressure region. The enthalpies of vaporization obtained by direct calorimetric method and those ones calculated from the vapor pressure are compared for justifying their reliability. An interconnection between the properties derived from the vapor pressure and some structural parameters of the substances are

Part 3 considers the low-temperature adiabatic calorimetry for measuring the heat capacity and studying the properties of the phase transitions. Experimental technique has been presented by modern completely automated adiabatic calorimeter used in LLT. Experimental determination and mathematical processing of the phase transitions were given including an X-ray analysis of crystal structure and the infrared and Raman spectroscopy for interpretation of the processes occurring during the solid-phase transitions. Main thermodynamic functions (changes of the entropy, enthalpy, and Gibb's energy) in

many areas of science, technology, and medicine (Varushchenko et. al., 2007).

perfluorocarbons to their hydrocarbon counterparts.

some functional organic compounds.

analyzed.

mostly on the LLT-school.

condensed states were calculated on the basis of the heat capacities and the properties of the solid-to-solid transitions and fusion.

Part 4 deals with 1) determination of the ideal gas thermodynamic functions by experimental and theoretical methods, 2) verification of the thermodynamic functions by comparing the absolute entropies calculated on the basis of the third thermodynamic law and by statistical thermodynamics, and 3) the methods of extending the saturated vapor pressure of the "atmospheric" range of pressure to entire region of liquids from the triple to the critical temperatures.

Parts 5, 6, 7, and 8 present Conclusion, Acknowledgments, References, and Appendix, respectively.
