The Reaction of C-NO2 with CO

In this chapter we discussed the transition metal catalyzed oxidative carbonylation of alkenes, alkynes and organometallic reagents. In these types of reactions, an additional oxidant is needed to reoxidize the catalyst back to an active state after a reductive elimination step. The oxidants applied are normally Cu(OAc)2 or BQ, air or O2, as more green oxidants should be investigated and applied in oxidative carbonylation reactions. In contrast, carbonylative reduction reactions using CO as a reductant are also interesting. In the next chapter, the reduction of C-NO2 with CO will be discussed. 

Marchand and co-workers reported a synthetic route to TNAZ (18) involving a novel electrophilic addition of NO+ NO2 across the highly strained C(3)-N bond of 3-(bromomethyl)-l-azabicyclo[1.1.0]butane (21), the latter prepared as a nonisolatable intermediate from the reaction of the bromide salt of tris(bromomethyl)methylamine (20) with aqueous sodium hydroxide under reduced pressure. The product of this reaction, A-nitroso-3-bromomethyl-3-nitroazetidine (22), is formed in 10% yield but is also accompanied by A-nitroso-3-bromomethyl-3-hydroxyazetidine as a by-product. Isolation of (22) from this mixture, followed by treatment with a solution of nitric acid in trifluoroacetic anhydride, leads to nitrolysis of the ferf-butyl group and yields (23). Treatment of (23) with sodium bicarbonate and sodium iodide in DMSO leads to hydrolysis of the bromomethyl group and the formation of (24). The synthesis of TNAZ (18) is completed by deformylation of (24), followed by oxidative nitration, both processes achieved in one pot with an alkaline solution of sodium nitrite, potassium ferricyanide and sodium persulfate. This route to TNAZ gives a low overall yield and is not suitable for large scale manufacture. 

As is evident from experimental measurements, most kinds of nitrate esters appear to decompose to NOj and C,H,0 species with the breaking of the O-NOj bond as the initial step. A strong heat release occurs in the gas phase near the decomposing surface due to the reduction of NO2 to NO accompanied by the oxidation of C,H,0 species to HjO, CO, and COj. NO reduction, however, is slow and this reaction is not observed in the decomposition of some nitrate ester systems. Even when the reaction occurs, the heat release does not contribute to the heat feedback to the surface because the reaction occurs at a distance far from the surface. 

As an example, the reaction of nitrogen dioxide and carbon monoxide has been found to be second order with respect to NO2 and zero order with respect to CO below 225°C. 

We can most easily see the relationship between the slow step in a mechanism and the rate law for the overall reaction by considering an example in which the first step in a multistep mechanism is the rate-determining step. Consider the reaction of NO2 and CO to produce NO and CO2 (Equation 14.23). Below 225 °C, it is found experimentally that the rate law for this reaction is second order in NO2 and zero order in CO Rate = k[N02]. Can we propose a reaction mechanism consistent with this rate law Consider the two-step mechanism ... 

Nitrogen dioxide (NO2) is the only important gaseous species in the lower atmosphere that absorbs visible Ught. (a) Write the Lewis structure(s) for NO2. (b) How does this structure account for the fact that NO2 dimerizes to form N2O4 Based on what you can find about this dimerization reaction in the text, would you expect to find the NO2 that forms in an urban environment to be in the form of dimer Explain, (c) What would you expect as products, if any, for the reaction of NO2 with CO (d) Would you expect NO2 generated in an urban environment to migrate to the stratosphere Explain. 

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