Bestimmung der Bildungsenthalpie von Nitroxychlorid (Chlornitrat, NO3Cl) als Beitrag zur Deutung der Kinetik des thermischen NO3Cl-Zerfalls in der Gasphase und in der Lösungsphase / Determination of the Enthalpy of Formation of nitroxy Chloride (Chlorine Nitrate, NO3Cl). A Contribution to the Interpretation of the Kinetics of the Thermal Decomposition of NO3Cl in the Gas Phase and in Solution

The dissociation energy values ⊿H0298(ClO- NO2) = 25.87 kcal mol-1 and ⊿H0 0(ClO-NO2),0 = 24.8 kcal mol-1 were derived from the standard enthalpy of formation of nitroxy chloride (NO3CI) ⊿Hf0 = 6.28 kcalmol-1 which has been determined from the reaction enthalpy of the gas phase reaction NOCI + NO3CI = 2 NO2 + Cl2. With the help of these data it was possible to show that in the thermal decomposition of NO3Cl, for which the overall reaction is NO3Cl = NO2 +½O2 + ½Cl2. at temperatures around 100 °C the equilibrium NO3Cl ⇄ NO2 + OCl is established. At the beginning of the reaction, there exists such a high OCl concentration that the decomposition occurs practically exclusively by the reactions OCl + OCl + M ⇄Cl2O2 + M, Cl2O2 + M → Cl2 + O2+M and OCl + OCl → Cl + OOCl, the last of which is followed by Cl-consuming reaction steps, e.g. CI + NO3CI → NO3 + Cl2, apparently initiating chain reactions. The reaction step NO2 + NO3Cl → NO3 + NO2Cl, postulated from an investigation of the kinetics in a nono-polar inert solvent, and its daughter reactions probably occur for the gas phase reaction as well.