Thermochemical properties of dinitramidic acid salts

Abstract

Enthalpies of formation and solution of hydrazinium, guanidinium, aminoguanidinium, and triaminoguanidinium salts of nitric and dinitramidic (HN(NO 2 ) 2 , DN) acids were deter mined by combustion and solution calorimetry methods. Enthalpies of formation of respective cations in infinitely dilute aqueous solution were calculated using the enthalpy of formation of the nitrate ion. The enthalpy of formation of the DN acid anion was determined based on the enthalpy of formation and solution of the acid salts. The weight average enthalpy of formation of the DN acid anion equal to 8.40±0.13 kcal mol -1 was obtained. The enthalpy of solution of ammonium dinitramide (ADN) was measured (8.71±0.01 kcal mol -1 ). From these data, the enthalpy of formation of ADN was calculated (-32.14±0.14 kcal mol -1 ). The energy of com bustion of ADN was measured by the calorimetry method, and the enthalpy of formation of ADN was calculated for a sample with purity above 99.9% (-32.20±0.19 kcal mol -1 ). The weight average enthalpy of formation of ADN equal to -32.16±0.11 kcal mol -1 is recom mended for use. Enthalpies of formation of sodium, potassium, and cesium salts of DN acid were determined.Synthesis of salts of dinitramidic (DN) acid HN(NO 2 ) 2 can be considered as a significant achievement in the chemistry of nitro compounds. Ammonium dinitramide (ADN), which for the first time was synthesized at the N. D. Zelinsky Institute of Organic Chemistry, AS USSR, 1,2 and later in the USA, 3 is of practical interest.Calorimetric methods -calorimetry of combustion and reaction calorimetry -are widely used for the deter mination of thermochemical properties of DN salts in the present work. Joint application of the calorimetric meth ods allows not only determining the principal thermo chemical characteristics of the salt compounds, but also correlating of the calculated enthalpies of formation of the salts, which allows increasing reliability of these data.The enthalpy of formation of the salt is related to the enthalpies of formation of the constituent ions by follow ing equation:where Cat is a cation, An is an anion. The enthalpies of formation (ΔH°f[Cat•An] cr ) and so lution (ΔH°s ol [Cat•An] cr ) of the salt are in the left part of the Eq. (1), and the enthalpies of formation of the cat ion (ΔH°f[Cat + ] aq ) and the anion (ΔH°f[An -] aq ) in the infinitely dilute solution are in the right part of the equation. The enthalpy of formation of salts with composition C a H b O c N d can be found by combustion calorimetry ac cording to the following equation: ΔH°f[Cat•An] cr + ΔH°c[Cat•An] cr = = a•ΔH°f[CO 2 ] g + (b/2)ΔH°f[H 2 O] l .(2)Thus, the enthalpy of formation of an unknown ion can be calculated by Eq. (1), if the enthalpy of formation of the salt is determined beforehand from data on the combustion and the enthalpy of solution of the salt is measured.If there are several salts with the same ion, then the values of the enthalpy of formation of this ion, obtained according to Eqs (1) and (2), must be equal within the limits of measur...

Enthalpy of formation of guanidine and its amino and nitro derivatives

“…Using the experimental enthalpies of formation of guanidine [44] and its salts with inorganic and organic acids HA=HNO 3 , HClO 4 , HCl, HN(NO 2 ) 2 , and 3-nitro-1,2,4-triazol-5-one (NTO) [59][60][61], the difference…”

Heat of Formation of ADN‐Based Liquid Monopropellants

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