Energetic and structural properties of 4-nitro-2,1,3-benzothiadiazole

► Energetics of 4-nitro-2,1,3-benzothiadiazole: experimental computational study. ► ΔfHmo (cr) of 4-nitro-2,1,3-benzothiadiazole was measured by rotating combustion calorimetry. ► ΔcrgHmo of 4-nitro-2,1,3-benzothiadiazole was derived from vacuum drop microcalorimetric measurements. ► Molecular orbital calculations for 4-nitro-2,1,3-benzothiadiazole were done by G3(MP2)//B3LYP. The energetic study of 4-nitro-2,1,3-benzothiadiazole has been developed using experimental techniques together with computational approaches. The standard (p°=0.1MPa) molar enthalpy of formation of crystalline 4-nitro-2,1,3-benzothiadiazole (181.9±2.3kJ·mol−1) was determined from the experimental standard molar energy of combustion −(3574.3±1.3)kJ·mol−1, in oxygen, measured by rotating-bomb combustion calorimetry at T=298.15K. The standard (p°=0.1MPa) molar enthalpy of sublimation, at T=298.15K, (101.8±4.3)kJ·mol−1, was determined by a direct method, using the vacuum drop microcalorimetric technique. From the latter value and from the enthalpy of formation of the solid, it was calculated the standard (p°=0.1MPa) enthalpy of formation of gaseous 4-nitro-2,1,3-benzothiadiazole as (283.7±4.9)kJ·mol−1. Standard ab initio molecular orbital calculations were performed using the G3(MP2)//B3LYP composite procedure and several working reactions in order to derive the standard molar enthalpy of formation 4-nitro-2,1,3-benzothiadiazole. The ab initio results are in good agreement with the experimental data.