A kinetic study of the decomposition of monomeric nitrosomethane

The thermal decomposition of dimethyl ether, inhibited by nitric oxide and by propylene, was studied in the temperature range of 500 to 600' C. About 1.5 mm of nitric oxide gave maximal inhibition, the rate then being approximately 8% of the uninhibited rate. With propylene, approximately 70 mm gave maximal inhibition, the rate being slightly higher than that using nitric oxide (~1 2 . 5 7~ of the uninhibited rate). I n both cases the degree of inhibition was independent of the ether pressure. I n the maximally inhibited regions both reactions are three-halves order with respect to ether pressure. As the pressure of nitric oxide was increased beyond 10-15 mm, the overall rate increased, and in this region the reaction is first order with respect t o both nitric oxide and ether. A 50:50 mixture of CHaOCH3 and CD3OCD8, with enough NO to ensure maximum inhibition, was pyrolyzed. Even a t very low percentage decomposition the CD3H/CD4 ratio was approximately the same as that in the uninhibited deco~nposition, proving that the inhibited reaction is largely a chain process. Detailed inhibition mechanisms are proposed in which the inhibitor is involved both in initiation and termination reactions.

Section: Induction Periodmentioning

confidence: 99%

Kinetics and Mechanisms of the Pyrolysis of Dimethyl Ether: Ii. The Reaction Inhibited by Nitric Oxide and Propylene

McKenney¹,

Wojciechowski²,

Laidler³

1963

“…T h e heterogeneous component found in this work finds an analogue in surface effects which plagued the study of CHsNO decomposition (44). As for the homogeneous part of the reaction, it is convenient to Can.…”

mentioning

confidence: 93%

“…I t is assumed there that every methyl radical ends up as CH3NO (Section IIB), and that CH3NO decomposes only in a thirdorder reaction with NO t o yield nitrogen, or in a first-order reaction t o yield some other product (44). I t turns out that the kinetics depends on the relative magnitudes of kq and k3(NO)02, where kr is the first-order rate constant for the decomposition of C H 3 N 0 (believed to yield the oxime CH2=NOH as the first step (44)), k3 is the third-order rate constant for the process CHINO + 2 x 0 -+ IVYo + products, and (KO)o = initial concentration of nitric oxide.…”

mentioning

confidence: 99%

The Thermal Decomposition of Azomethane: I. Effect of Added Olefin and Nitric Oxide

Forst¹,

Rice²

1963

The addition of ethylene and propylene reduces the rate of azomethane decomposition as measured by the rate of nitrogen production, and also reduces the ratio CH4/N2 in the products, but the reduction in the value of both quantities is different for each of the two olefins. I n 10070 decomposition, ethylene and propylene both increase somewhat the ratio (nitrogen recovered)/(azomethane decomposed). These results are interpreted to mean that there is in fact a short chain in the pyrolysis, but that ethylene and propylene are unsuitable inhibitors.The addition of a few millimeters of NO reduces the rate t o a minimum which is lower than that with added propylene or ethylene (apparent chain length 2 to 3), but further addition of NO increases the rate again. Identical result is obtained in a packed vessel. The yield of methane, ethane, and ethylene is reduced t o almost zero with a sufficient amount of KO. The ratio (NO consumed)/(nitrogen produced) reaches the value of two in the neighborhood of the rate minimum. I t is concluded t h a t the net inhibited rate, i.e. rate corrected for the stimulatory effect of NO, refers to the initial unimolecular process C H~N Z C H ZThe rate a s well a s the activation energy of this process is found t o be pressure dependent.I t is shown by the use of the isotopic nitric oxide ISNO that about one-half of the rate increase a t higher NO pressures is due to nitrogen produced from NO. The remainder of the rate increase is accounted for by a NO-induced decomposition of azomethane.

“…The alkyl free radicals produced in reaction [3] react with nitric oxide t o form the corresponding nitroso compounds (19)(20)(21)(22)(23)(24)(25) : alkyl nitroso dimers as shown in step [5]; (2) isomerization to the corresponding oxime (reaction [6]) ; (3) further reaction with nitric oxide (reaction [7]):…”

Section: Discussionmentioning

confidence: 99%

“…Reaction [5] is slow (5,6,27) and the dimer formed is not capable of further reactions (5,6). The isomerization reaction, [6], has an activation energy of 39 kcal in the case of nitrosomethane (6) but it may proceed rapidly in ultraviolet light or in the presence of an active surface (6,28).…”

Section: Discussionmentioning

confidence: 99%

The Reactions of Electronically Excited Nitric Oxide Molecules With Hydrocarbons

Strausz¹,

Gunning²

1963

The reactions of NO(411) molecules, generated by Hg 6(3P1) photosensitization, with methane, ethane, propane, neopentane, and benzene have been studied a t room temperature in a circulatory system. I n the case of ethane the following reaction products were identified: Nz, NzO, HzO, NOz, CO, Con, CzHa, acetaldehyde, nitroethane, ethyl nitrite, ethyl nitrate, nitroethylene, nttromethane, methyl nitrite, methyl nitrate, formaldehyde. For hydrocarbon consumption, under comparable conditions, the following quantum yield values were established: *-P--(c~H~) < 0.04, *-P--(cH~) > 0.045, *-)--(c~H~) > 0.063, @-)-(,eow,~,e) h . 0.1 mole/einstein. The most probable primary process may be represented by the sequenceAlkyl free radicals catalyze the chain disproportionation of nitric oxide a t room temperature according to the stoichiotnetric equationA minimal value of 12 was established for the average chain length.