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

The 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 k 1 (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 k 2 (sec −1 ) = 15.8 − 39.3 kcal/mole/2.3 RT . From Δ S 1,−1 0 and Δ S 2,−2 0 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 d 3 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 × 10 5 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 NO 2 , the yield of methyl nitrate indicates that the combination of methoxy radicals with NO 2 is in the high‐pressure limit at atmospheric pressure.