KINETICS AND MECHANISMS OF THE THERMAL DECOMPOSITION OF PROPIONALDEHYDE: PART II. THE REACTION IN THE PRESENCE OF NITRIC OXIDE

The decomposition of propionaldehyde in the presence of various amounts of nitric oxide has been studied in the temperature range 520–560 °C and at propionaldehyde pressures from 30 to 300 mm Hg. The reaction is inhibited by small amounts of nitric oxide, and larger amounts give rise to strong catalysis. The order of the maximally inhibited reaction is 1.5 and the degree of inhibition decreases with an increase of propionaldehyde pressure. In the catalytic region the order of the overall reaction is 1.25 with respect to propionaldehyde, and the relative rate (the ratio of rates in the presence and absence of nitric oxide) is independent of propionaldehyde pressure. The overall rate in the catalytic region can be expressed as[Formula: see text]the unit of concentration being mole per cc. A mechanism in which nitric oxide initiates chains by the reaction C 2 H 5 CHO + NO → C 2 H 5 CO + HNO, propagates them by C 2 H 5 NO + C 2 H 5 CHO → C 2 H 6  + C 2 H 5 CO + NO, and terminates them by C 2 H 5  + C 2 H 5 NO → C 4 H 10  + NO and C 2 H 6  + C 2 H 4  + NO and C 2 H 5 NO + C 2 H 5 NO → C 4 H 10  + 2NO or C 2 H 6  + C 2 H 4  + 2NO is proposed and is shown to be consistent with the results.