ChemInform Abstract: THE GAS‐PHASE PYROLYSIS OF ALKYL NITRITES. III. ISOPROPYL NITRITE

Abstract

The rate of decomposition of isopropyl nitrite (IPN) has been studied in a static system over the temperature range of 130–160°C. For low concentrations of IPN (1–5 × 10−5M), but with a high total pressure of CF4 (∼0.9 atm) and small extents of reaction (∼1%), the first-order rates of acetaldehyde (AcH) formation are a direct measure of reaction (1), since k3 » k2(NO): Addition of large amounts of NO (∼0.9 atm) in place of CF4 almost completely suppressed AcH formation. Addition of large amounts of isobutane – t-BuH – (∼0.9 atm) in place of CF4 at 160°C resulted in decreasing the AcH by 25%. Thus 25% of were trapped by the t-BuH (4): The result of adding either NO or t-BuH shows that reaction (1) is the only route for the production of AcH. The rate constant for reaction (1) is given by k1 = 1016.2±0.4–41.0±0.8/θ sec−1. Since (E1 + RT) and ΔH°1 are identical, within experimental error, both may be equated with D(i-PrO-NO) = 41.6 ± 0.8 kcal/mol and E2 = 0 ± 0.8 kcal/mol. The thermochemistry leads to the result that From ΔS°1 and A1, k2 is calculated to be 1010.5±0.4M−1·sec−1. From an independent observation that k6/k2 = 0.19 ± 0.03 independent of temperature we find E6 = 0 ± 1 kcal/mol and k6 = 109.8+0.4M−;1·sec−1: In addition to AcH, acetone (M2K) and isopropyl alcohol (IPA) are produced in approximately equal amounts. The rate of M2K formation is markedly affected by the ratio S/V of different reaction vessels. It is concluded that the M2K arises as the result of a heterogeneous elimination of HNO from IPN. In a spherical reaction vessel the first-order rate of M2K formation is given by k5 = 109.4–27.0/θ sec−1: IPA is thought to arise via the hydrolysis of IPN, the water being formed from HNO. This elimination process explains previous erroneous results for IPN.