The gas‐phase pyrolysis of alkyl nitrites. IV. Ethyl nitrite

Abstract

The rate of decomposition of ethyl nitrite (EN) has been studied in a static system over the temperature range of 162‐218°C. The main products are formaldehyde, acetaldehyde, ethanol, and nitrous oxide. For low concentrations of EN (10−5‐10−4M), but with a high total pressure of CF4 (∼0.9 atm) and small extents of reaction (2‐6%), the first‐order homogeneous rates of CH2O formation are a direct measure of reaction (1), since k3bk2(NO): Addition of large amounts of NO(∼0.9 atm) completely suppressed CH2O formation in agreement with the observed value for k3b. The rate of reaction (1) is given by k1 = 1016.0‐41.8/θ−1. Since (E1 + RT) and ΔH±1 are identical, both may be equated with D(EtO‐NO) = 42.4 ± 0.9 kcal/mol and E2 = O± 1 kcal/mol. The thermochemistry leads to the result ΔHDelta;f(EN) = ‐24.5 ± 1 kcal/mol. From ΔS1 and A1, k2 is calculated to be 1010.3M−1θ−1. From an independent observation that k6/k2 = 0.3 ± 0.05 independent of temperature it is concluded that k6 = 109.8M−1Δ−1. The addition of NO has no effect on the AcH yields. Although the yields of AcH are affected by the surface‐to‐volume ratio of different reaction vessels, it is concluded that in a spherical reaction vessel, the AcH arises as the result of an essentially homogeneous elimination of HNO from EN(5): and reaction (6). The rate of AcH formation is given by kobs = 1013.7‐37.5/θ−1. By using isobutane (t‐BuH) as a radical trap for EtO (4), a value for k3b was determined to be 1015.0‐21.6/θ s−1. From an independent observation that k2:k2:k6:k6 was 1: 0.4: 0.3: 0.18 we find k2θ = 109.9M−1→ s−1, k1θ = 1016.0‐40.0/θ s−1, and k6± = 109.6M−1 · s−1.

Alkoxy radicals in the gaseous phase: β-scission reactions and formation by radical addition to carbonyl compounds

“…Their E a value (73.6 kJ mol -1 ) is slightly higher than ours and their derived log A value (12.99) is significantly lower than ours (13.60). Their predicted rate constant at 300 K (1.46 s -1 ) is in close agreement with the value of Batt and Milne (44). β-Scission of the ethoxy radical yielding CH 3 · + CH 2 =O is predicted to be endothermic by 40.6 kJ mol -1 at 0 K and 47.8 kJ mol -1 at 298 K (Table 3).…”

“…Our predicted rate constant (k = 19 s -1 ) is higher than the experimental values of Viskolcz and co-workers (14) (5.2 s -1 ) and Batt and Milne (44) (1.5 s -1 ). This reaction has also been investigated by Somnitz and Zellner (20) at a modified G2 level of theory, using RRKM theory to derive Arrhenius activation parameters and reaction rate constants.…”

Sensitizing effects of NOx on CH4 oxidation at high pressure

“…Following the recent recommendation by Atkinson et al [98], the fall-off behavior is described using the low-pressure limit k 9,0 from a study by Daële et al [99] at 295 K with an estimated center-broadening factor of F cent,9 = 0.6. Daële et al [99] also considered the bimolecular channel NO + C 2 H 5 O HNO + CH 3 CHO (R8) and determined the constant rate coefficient k 8 = (6.6 ± 3.0) × 10 12 cm 3 /mol s, in good agreement with the measured branching ratio k 8 /k 9,∞ = 0.3 from Baker and Shaw [100] and the value 6 × 10 12 cm 3 /mol s from the indirect study of Batt and Milne [101].…”

Atmospheric reactions of alkoxy and ?-hydroxyalkoxy radicals

“…Choo and Benson [11], however, presented data indicating that the parameter a in the above relationship depends on the alkyl leaving-group, with the parameter a decreasing monotonically along the alkyl leaving-group series Ċ H 3 , Ċ 2 H 5 , (CH 3 ) 2 Ċ H, and (CH 3 ) 3 Ċ and depending on the ionization potential of the alkyl leaving-group. Batt and co-workers [31 -38] and Dóbé et al [39] have measured the rate constants for the decomposition of the ethoxy [34], 2-propoxy [33], 2-butoxy [32], tert-butoxy [31,36 -38], 2-pentoxy [39], and 2methyl-2-butoxy [35] radicals relative to the alkoxy radical combination reaction with NO.…”