Kinetic and Mechanistic Study of the Thermal Decomposition of Ethyl Nitrate

Thermal decomposition of ethyl nitrate (ENT; CH 3 CH 2 ONO 2 ) 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 (CH 3 radical). The fit of the observed falloff curves with two‐parameter expressionk 1 =k 0 k ∞ [ M ]k 0 [ M ] + k ∞× 0 . 6 ( 1 + ( log (k 0 [ M ]k ∞ ) ) 2 ) − 1provided the following low‐ and high‐pressure limits for the rate constant of ENT decomposition: k 0 = 1.0 × 10 −4 exp(−16,400/ T ) cm 3 molecule −1 s −1 and k ∞ = 1.08 × 10 16 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–NO 2 bond cleavage leading to formation of NO 2 and CH 3 CH 2 O radical, which rapidly decomposes to form CH 3 and formaldehyde as final products. The yields of NO 2 , CH 3 , and formaldehyde upon decomposition of ethyl nitrate were measured to be near unity. In addition, the kinetic data were used to determine the O–NO 2 bond dissociation energy in ENT: 38.3 ± 2.0 kcal mol −1 .