The gas phase pyrolysis of alkyl nitrites. I. t ‐butyl nitrite

The rate of decomposition of t ‐butyl nitrite (TBN) has been studied in a static system over the temperature range of 120–160°C. For low concentrations of TBN (10 −5 ‐ 10 −4 M ), but with a high total pressure of CF 4 (∼0.9 atm) and small extents of reaction (∼1%), the first‐order homogeneous rates of acetone (M 2 K) formation are a direct measure of reaction (1), since k 3 » k 2 (NO): TBN . Addition of large amounts of NO in place of CF 4 almost completely suppresses M 2 K formation. This shows that reaction (1) is the only route for this product. The rate of reaction (1) is given by k 1 = 10 16.3–40.3 /θ s −1 . Since ( E 1 + RT ) and Δ H   ° 1are identical, both may be equated with D (RO‐NO) = 40.9 ± 0.8 kcal/mole and E 2 = O ± 1 kcal/mole. From Δ S   ° 1and A 1 , k 2 is calculated to be 10 10.4 M −1 ·s −1 , implying that combination of t BuO and NO occurs once every ten collisions. From an independent observation that k 2 / k 2 ′ = 1.7 ± 0.25 independent of temperature, it is concluded that k 2 ′ = 10 10.2 M −1 · s −1 and k 1 ′ = 10 15.9−40.2 /θ s −1 ;. This study shows that MeNO arises solely as a result of the combination of Me and NO. Since NO is such an excellent radical trap for t ‐Bu \documentclass{article}\pagestyle{empty}\begin{document}${\rm Me\dot O}$\end{document} , reaction (2) may be used in a competitive study of the decomposition of t Bu \documentclass{article}\pagestyle{empty}\begin{document}${\rm Me\dot O}$\end{document} in order to obtain the first absolute value for k 3 . Preliminary results show that k 3 (∞) = 10 15.7–17.0 /θ s −1 . The pressure dependence of k 3 is demonstrated over the range of 10 −2 −1 atm (160°C). The thermochemistry for reaction (3) implies that the Hg 6( 3 P 1 ) sensitised decomposition of t ‐BuOH occurs via reaction (m):In addition to the products accounted for by the TBN radical split, isobutene is formed as a result of the 6‐centre elimination of HONO: TBN \documentclass{article}\pagestyle{empty}\begin{document}$\mathop \to \limits^7 $\end{document} isobutene + HONO. The rate of formation of isobutene is given by k 7 = 10 12.9–33.6 /θ s −1 . t ‐BuOH, formed at a rate comparable to that of isobutene–at least in the initial stages–is thought to arise as a result of secondary reactions between TBN and HONO. The apparent discrepancy between this and previous studies is reconciled in terms of the above parallel reactions (1) and (7), such that k + 2 k 7 = 10 14.7–36.2 /θ s −1 .