The very‐low‐pressure pyrolysis (VLPP) of n‐propyl nitrate, tert‐butyl nitrite, and methyl nitrite. Rate constants for some alkoxy radical reactions

Abstract

AbstractThe pyrolysis of n‐propyl nitrate and tert‐butyl nitrite at very low pressures (VLPP technique) is reported. For the reaction the high‐pressure rate expression at 300°K, log k1 (sec−1) = 16.5 − 40.0 kcal/mole/2.3 RT, is derived. The reaction was studied and the high‐pressure parameters at 300°K are log k2(sec−1) = 15.8 − 39.3 kcal/mole/2.3 RT. From ΔS1,−10 and ΔS2,−20 and the assumption E−1 and E−2 ⋍ 0, we derive log k−1(M−1·sec−1) (300°K) = 9.5 and log k−2 (M−1·sec−1) (300°K) = 9.8. In contrast, the pyrolysis of methyl nitrite and methyl d3 nitrite afford NO and HNO and DNO, respectively, in what appears to be a heterogeneous process. The values of k−1 and k−2 in conjunction with independent measurements imply a value at 300°K for of 3.5 × 105 M−1·sec−1, which is two orders of magnitude greater than currently accepted values.In the high‐pressure static pyrolysis of dimethyl peroxide in the presence of NO2, the yield of methyl nitrate indicates that the combination of methoxy radicals with NO2 is in the high‐pressure limit at atmospheric pressure.