Thermodynamic Characteristics of Ethyl-2-cyano-3-(furan-2-yl)-prop-2-enoate Derivatives Roman Kos, Iryna Sobechko, Yuriy Horak, Valentin Sergeev, Volodymyr Dibrivnyi Department of Physical and Colloid Chemistry, National University Lviv Polytechnic, Ukraine Email: romankos.ua@gmail.com Abstract. Using bomb calorimetry and Knudsen effusion methods the enthalpic characteristics in condensed state of ethyl-2-cyano-3-(furan-2-yl) prop-2-enoate derivatives were experimentally determined. The values of the enthalpies of formation in the gas state of investigated esters were calculated taking into account the values of the enthalpies of sublimation adjusted to 298K. From obtained thermochemical values we defined new group contributions which can be added to the Benson’s additive scheme. Using these increments the enthalpies of formation of investigated compounds in gas state were theoretically calculated and their differences from the experimentally determined were analyzed. Keywords: Bomb calorimetry, effusion method, Benson’s scheme 1 Introduction Heterocyclic compounds are widely distributed in nature [1]. Many of them are particularly important for living organisms and they serve as a key components of biological processes. Many of drugs are derived from natural products, but their number is much greater than those synthesized from natural or synthetic compounds [2]. In particular, furan derivatives are commonly used in the synthesis of biologically active compounds that exhibit antibacterial, antitumor, and tuberculostatic action [3]. Determination of thermodynamic properties of substances with widespread use will help to optimize the processes of their synthesis and processing, as well as providing an opportunity to explore the energetic properties of molecules of this class. Considering these diverse information the need of a greater number of values of thermochemical parameters for esters of furanacrylic acid becomes evident. Despite this there are no reported in literature values of the standard molar enthalpies of formation in the crystalline and gas phase, as well as the standard molar enthalpies of sublimation of investigated compaunds. The present study provides results of the purification, standard molar energy of combustion, standard molar enthalpy of sublimation, and standard molar enthalpy of formation in both crystalline and gaseous states, T = 298.15 K, for the five compounds. The experimental determination of the standard energies of combustion of the five esters in oxygen at T = 298.15 K was conducted using static-bomb combustion calorimetry. From the temperature dependence of the vapour pressure using linear form of the Clausius–Clapeyron equation, the standard molar enthalpies of sublimation, at the average temperature were derived. Standard molar enthalpies and entropies of sublimation at the temperature of 298.15 K were calculated using estimated values for the heat capacity differences between the gas and the crystal phases of each compound. From the experimental values of the standard molar enthalpies of formation in the condensed phase and the values of the standard molar enthalpies of sublimation at T = 298.15 K the standard molar enthalpies of formation in the gaseous phase were calculated for the five ethyl esters of furanacrylic acid derivatives. Due to the wide use of thermochemical characteristics of organic compounds, it is important to find the best theoretical approach for determining these properties, when experimental determination is impossible. Therefore we compared in this work the experimental data with Benson’s additive scheme [4]. For thermochemical studies we selected number of ethyl esters of furan acrylic acid derivatives: 74 Modern Organic Chemistry Research, Vol. 2, No. 2, May 2017 https://dx.doi.org/10.22606/mocr.2017.22006 MOCR Copyright © 2017 Isaac Scientific Publishing