Thermochemistry of organic azides revisited

•Pure samples of 4-nitro-phenyl azide, 1-octyl- and 1-decyl-azides were prepared.•Vapour pressures, sublimation and vaporization enthalpies measured by transpiration.•Enthalpy of formation of 1-alkyl azides measured by combustion calorimetry.•Enthalpy of fusion of 4-nitro-phenyl azide measured by DSC.•Experimental gas enthalpies of formation were in agreement with calculated by G4.

Highly pure samples of 4-nitro-phenyl azide, 1-octyl azide and 1 decyl-azide were prepared for thermochemical studies. Vapour pressures over the solid and the liquid sample of 4-nitro-phenyl azide have been determined by the transpiration method. The molar enthalpies of vaporization/sublimation for this compound were derived from the temperature dependencies of vapour pressures. The molar enthalpy of fusion of 4-nitro-phenyl azide was measured by DSC. The measured data set for 4-nitro-phenyl azide was successfully checked for internal consistency. Molar enthalpies of vaporization of 1-octyl azide and 1 decyl-azide were measured by transpiration. The molar enthalpies of formation of the liquid 1-octyl azide and 1 decyl-azides were derived from the combustion calorimetry. New experimental results for these organic azides have been used to derive their molar enthalpies of formation in the gas state and for comparison with results from quantum-chemical method G4.