Kinetic and Mechanistic Study of the Thermal Decomposition of Ethyl Nitrate

Thermal decomposition of ethyl nitrate (ENT; CH₃CH₂ONO₂) has been studied in a low‐pressure flow reactor combined with a quadrupole mass spectrometer. The rate constant of the nitrate decomposition was measured as a function of pressure (1–12.5 Torr of helium) and temperature in the range 464–673 K using two different approaches: from kinetics of ENT loss and those of the formation of the reaction product (CH₃ radical). The fit of the observed falloff curves with two‐parameter expression provided the following low‐ and high‐pressure limits for the rate constant of ENT decomposition: k ₀ = 1.0 × 10⁻⁴ exp(−16,400/T ) cm³ molecule⁻¹ s⁻¹ and k _∞ = 1.08 × 10¹⁶ exp(−19,860/T ) s⁻¹, respectively, which allow to reproduce (via above expression and with 20% uncertainty) all the experimental data obtained for k ₁ in the temperature and pressure range of the study. It was observed that the initial step of the thermal decomposition of ethyl nitrate is O–NO₂ bond cleavage leading to formation of NO₂ and CH₃CH₂O radical, which rapidly decomposes to form CH₃ and formaldehyde as final products. The yields of NO₂, CH₃, and formaldehyde upon decomposition of ethyl nitrate were measured to be near unity. In addition, the kinetic data were used to determine the O–NO₂ bond dissociation energy in ENT: 38.3 ± 2.0 kcal mol⁻¹.