CH3ONO

Typical reaction products of NO removal in non-thermal plasma in the presence of propylene, predicted by the model in Martin et al. and Dorai and Kushner [86,88], include formaldehyde (HCHO), acetaldehyde (CH3CHO) methyl oxirane (C3H60), gly-coxal (CHO-CHO), methyl nitrite (CH3ONO), methyl nitrate (CH30N02), and 2-nitroso ethanal (ONCH2CHO). 

The most common sources of OH used for relative rate studies include the photolysis of HONO (e.g., see Cox, 1975) or alternatively methyl nitrite (CH3ONO) in air in the presence of NO (Atkinson et al., 1981) ... 

Methyl nitrite (CH3ONO) MNIT High-molecular-weight aromatic oxidation ... 

Shaw and Trotman-Dickenson (34) investigated the simultaneous reaction of methoxy radicals with two hydrocarbons. The methoxy radicals were generated by pyrolysis of either CH3ONO at 300° to 400°C. 

The C02 acts as an internal actinometer for CH3 radical production. They monitored their products by infrared and gas chromatographic analysis. From the production of CH3N02, N2, CH3ONO, and CH3ONOa, they found that, at 90°C, N02 was five times as effective as NO in scavenging CH3 radicals. They also found that both reactions were third order below 100 torr pressure, but second order above 100 torr. 

Phillips and his co-workers have studied the reactions of alkoxy radicals between 95 and 240°C. The pyrolysis of CH3ONO at 150-240°C was examined, and CH20 was formed above 180°C.343 Thus, reaction (27) plays some role at elevated temperatures for CH30 radicals. (NO is produced in the pyrolysis.) In unpublished work (as reported in ref. 6), Phillips found that, in the pyrolysis of (CH30)2-NO mixtures, k27/k26 = 0.5 at 174°C. 

CH300 + HO, - CH3OOH + 02 ch3o + NO-CH3ONO ch3o + no2 -ch3ono2... 

In order to establish the mechanisms for reactions (14a) and (14b), experiments were designed to uniquely identify CHsOO and HCHO as the primary products. For this purpose, HO radicals could be generated from C2H5ONO but not from CH3ONO, since the latter nitrite produced HCHO as a major product. Also, the CHsOO radical could lead to the formation of HCHO via CHsOO + NO - CHaO + N02 followed by CH30 + 02 - HCHO + HOO. However, it was possible to adjust the 02 pressure and NO concentrations so that the CHsO radicals reacted competitively with 02, NO and N02 ... 

CH,CN (methyl cyanide) CH3N(.)2 (nitromethane) CH3ONO (methyl nitrite) CH3SiH3 (methyl silane) HCOOH (formic acid) 1ICOOCH, (methyl formate) CFi3CONH2 (acetamide) C2H4NH (aziridine)... 

The Si PES, calculated by Nonella and Huber (1986), has a shallow minimum above the ground-state equilibrium, or expressed differently, a small potential barrier hinders the immediate dissociation of the excited S complex. Although the height of the barrier is less than a tenth of an eV, it drastically affects the dissociation dynamics, even at energies which significantly exceed the barrier. The excited complex lives for about 5-10 internal NO vibrational periods before it breaks apart. The photodissociation of CH3ONO through the Si state exemplifies indirect photodissociation or vibrational predissociation (Chapter 7). 

In indirect photofragmentation, on the other hand, a potential barrier or some other dynamical force hinders direct fragmentation of the excited complex and the lifetime amounts to at least several internal vibrational periods. The photodissociation of CH3ONO via the 51 state is a representative example. The middle part of Figure 1.11 shows the corresponding PES. Before CH30N0(5i) breaks apart it first performs several vibrations within the shallow well before a sufficient amount of energy is transferred from the N-0 vibrational bond to the O-N dissociation mode, which is necessary to surpass the small barrier. 

CH3ONO (Benoist d Azy, Lahmani, Lardeux, and Solgadi 1985 Briihlmann and Huber 1988). 

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