Russian Chemical Bulletin, International Edition, Vol. 68, No. 10, pp. 1856—1859, October, 2019 1856 Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1856—1859, October, 2019. 1066-5285/19/6810-1856 © 2019 Springer Science+Business Media, Inc. Experimental determination of the standard enthalpy of formation of 4H,8H-bis(furazano)[3,4-b:3´,4´-e]pyrazine and evaluation of its performance as a dispersant of solid fuels D. B. Lempert, a A. I. Kazakov, a A. B. Sheremetev, b A. G. Gladyshkin, b A. V. Nabatova, a and L. S. Yanovskii a,c a Institute of Problems of Chemical Physics, Russian Academy of Sciences, 1 prosp. Akad. Semenova, 142432 Chernogolovka, Moscow Region, Russian Federation. E-mail: lempertdavid@yandex.ru b N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., 119991 Moscow, Russian Federation. E-mail: sab@ioc.ac.ru c Department of Chemistry, M. V. Lomonosov Moscow State University, Build. 3, 1 Leninskie Gory, 119991 Moscow, Russian Federation The energy of combustion H c of 4H,8H-bis(furazano)[3,4-b:3´,4´-e]pyrazine (BFP) was measured by calorimetry in the oxygen atmosphere and the standard enthalpy of formation ΔH f was calculated. The real H f value was found to be 33 kJ mol –1 higher than reported before. The obtained results were used for correction of the evaluated efciency of using BFP as a solid fuel dispersant for rocket ramjet engines, which showed high BFP performance. Key words: furazan, pyrazine, enthalpy of combustion, enthalpy of formation, rocket fuel, rocket ramjet engines, dispersant. Studies of 4H,8H-bis(furazano)[3,4-b:3´,4´-e]pyrazine (BFP) were reported in publicly accessible literature in 1996 by two independent research teams. 1,2 Being a ther- mally stable compound (m.p. 296 C (dec.) 2—4 ) with a high density (d = 1.963 g cm –3 at 25 C 5 ), BFP is of interest as a component of energetic materials (explosives 4,6 and fuels for various applications 6,7 ) and as a precursor for the synthesis of other energetic compounds. 8—17 Early infor- mation on the synthesis and reactivity of BFP and its analogues are considered in a review. 18 Recently it was shown that high-enthalpy polynitro- gen compounds with relatively low oxygen content are of interest as components of solid fuel dispersants for rocket ramjet engines. 7,19 The role of the dispersant com- position is that the heat released upon its thermal degrada- tion heats the whole fuel (various hydrocarbons, boron compounds, etc.) to a high temperature at which the fuel is initially converted, in the gas generator, to a heated mixture of gases and dispersed solids. This mixture flows to the afterburner chamber and reacts there with hot air. The energy released upon the overall fuel con- version (both conversion in the gas generator and air combustion of the products in the afterburner chamber) ensures the rocket propulsion. It was shown that BFP is one of the best potential dispersant components among quite a few polynitrogen compounds considered for this purpose. 7 All characteristics of a dispersant component must be determined as accurately as possible. This forms the grounds for rational use of the component in order to attain its maximum efciency. An important characteristic of energetic compounds is the enthalpy of formation. Previously, 7 the relative efciency of a BFP-based dispersant was calculated using the only experimental value, namely, the enthalpy of formation of BFP (H f ) in the solid phase presented in the ICT database of thermo- chemical values 20 and equal to 390.4 kJ mol –1 . Also, two theoretical solid phase ΔH f values of BFP were reported in the literature, one calculated 21 by an additive scheme and fully coinciding with the reported experimental value 20 and one calculated by a quantum chemical method and equal to 420.6 kJ mol –1 . 22 What is the actual enthalpy of formation of this compound? This characteristic directly afects the energy performance of individual compounds and compositions. The modern rocket engineering requires high-precision thermochemical characteristics of components; otherwise, it is impossible to correctly solve applied problems. In this connection, the purpose of the present study is to measure the enthalpy of formation of BFP in the standard state by bomb combustion calorimetry. The measurements showed that previously published values were underestimated and, hence the use of BFP would result in a diferent per- formance of a rocket engine.