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H CH3

Most of the products predicted by this reaction scheme have been observed in laboratory studies, including dimethylnitramine [(CH3)2NN02], HONO, tetrameth-ylhydrazine [(CH3)2NN(CH3)2], and small amounts of methylformamide as products of the photooxidation of dimethylamine (e.g., see Pitts et al., 1978; and Tuazon et al., 1978). In addition, HCHO, CO, and small amounts of dime thy lformamide were identified in these studies.

It is noteworthy that the dimethylamino radical reaction with 02 is about a factor of ~ 106—107 slower than its reactions with NO and N02. For example, Lindley et al. (1979) measured the ratio of rate constants &8,A82 = 1.5 X 10~6 and &8I/A:83a = 3.9 X 10-7. Thus, at ~ 10 ppb NOx, reactions of the nitrogen-centered radical with NO and N02, in addition to 02, become important. This is perhaps not surprising, given that NH2 radicals also react extremely slowly with 02, with an upper limit of 6 X f0~21 cm3 molecule"1 s"1 (Tyndall et al., 1991).

There are few kinetic or product studies of the reactions of 03 with simple amines. Figure 6.20 shows the infrared spectrum of the products of the reaction of dimethylamine with 03 (Tuazon et al., 1994). The major products observed are CH3N = CH2, CH3N02, HCHO, CH3NHCHO, (CH3)2NCHO, (CH3)2NCH2N(CH3)2, HCOOH, and C02. The major nitrogen-containing products were explained by Tuazon and co-workers by the following mechanism:The

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