Standard enthalpies of formation of dicyclopropyldinitromethane and tricyclopropylmethane
Introduction
Cyclic compounds are of interest in several major respects. Firstly, cyclization of hydrocarbons usually accompanies by considerable changes in their geometry, which lead to appearance of strain in the molecules and change in their enthalpies of formation. Therefore, polycyclic compounds containing cyclopropane fragments constitute the promising substances for study correlations between energetic parameters and molecular geometry [1], [2], [3], [4]. Secondly, the strain in three-membered rings leads to the appearance of a high and peculiar reactivity of these compounds, which manifests itself in numerous reactions of opening of small cycle, specific rearrangements and isomerizations. This allows to perform syntheses of complex molecules with a specified combination of functional groups [5], [6], in particular, drugs antitumor [7] and antibacterial [8], [9]. Thirdly, three-membered cycles are found in the structures of a number of natural compounds [10], [11]. Cyclopropanes are interesting in the formation of conformationally rigid amino acids and peptides [12], [13].
In this work, enthalpies of formation at T = 298.15 K for two compounds containing cyclopropane fragments: dicyclopropyldinitromethane (DCPDNM) and tricyclopropylmethane (TCPM) in liquid and ideal gas states were obtained.
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Samples
The samples of dicyclopropyldinitromethane (C7H10N2O4(liq), DCPDNM) and tricyclopropylmethane (C10H16(liq), TCPM) (Fig. 1) were synthesized in the laboratory of organic synthesis of Chemical Department of Lomonosov Moscow State University. The substances were purified by distillation and preparative g.l.c. (Table 1). In the TCPM, traces of water were found; its amounts were determined by the analysis by the Fisher method and taken into account in the calculations of combustion energy. Purity of
Conclusions
The experimental determination of the formation enthalpies of the DCPDNM and TCPM in the liquid state by the method of bomb calorimetry was supplemented by calculating the formation enthalpies in the gaseous state, using the isodesmic reactions and estimating the enthalpies of vaporization by the molecular electrostatic potential method (MEP), which predicts well the enthalpies of vaporization (Table 4). The values of the formation enthalpies obtained by the calculation methods (Table 7)
Acknowledgements
This research was supported by the Russian Foundation for Basic Research under Grant No. 17-03-00449.
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