Nitrosomethane reaction with

The concoitradon of CHjNO decreased monotonically with temperature, but even at 800 °C a small concentration could be detected. The decrease could be due to unimolecular reactions, to biomolecular reactions with either CH,- or NO, or to a reverse reaction, CH3NO - CHj + NO. It is reasonable to assume that similar gas phase reactions would occur at much higher pressures however, we have not detected CH3NO during our catalytic experiments over the Sr/LajOj catalyst. Perhaps at much larger concentrations of NO the reaction CHjNO + NO - N O + CHjO- rapidly removes the nitrosomethane. 

For the first time, the primary nitrone (formaldonitrone) generation and the comparative quantum chemical analysis of its relative stability by comparison with isomers (formaldoxime, nitrosomethane and oxaziridine) has been described (357). Both, experimental and theoretical data clearly show that the formal-donitrones, formed in the course of collision by electronic transfer, can hardly be molecularly isomerized into other [C,H3,N,0] molecules. Methods of quantum chemistry and molecular dynamics have made it possible to study the reactions of nitrone rearrangement into amides through the formation of oxaziridines (358). 

Nitrosomethane (1) is known to be less stable than its isomer formaldoxime 2 and original attempts to isolate this species failed owing to its facile isomerization to the oxime 2. Already Bamberger and Seligman considered in 1903 that it would be difficult to isolate nitrosomethane after oxidation of methylamine due to its rapid isomerization to 2. Hence, 2 is always present in the synthesis of the nitrosomethane. Nitrosomethane is produced in the pyrolysis or photolysis of tcrf-butyl nitrite and by the reaction of methyl radicals with nitric oxide. Early results were confusing since the final product obtained is dimeric nitrosomethane. It was first isolated in 1948 by Coe and Doumani from the photolysis of gaseous ferf-butyl nitrite according to the overall reaction shown in equation 2. 

A related procedure, which may be of value from the preparative standpoint, involves the preparation of /rans-nitrosomethane dimer by adding a solution of diacetyl peroxide in sec-butyl nitrite to warm sec-butyl nitrite [50]. From the product of the reaction it has been assumed that this preparation involves the generation of free methyl radicals which react with the nitrite to give nitrosomethane and alkoxy radicals. The latter disproportionate to ketones and alcohols, while the nitroso compound dimerizes. 

Nitro-compounds fRNOj) are isomeric with nitrites, but their electronic structure, excited states and photochemistry are very different. There is no very low-lying (n.jt ) state, and nitroalkanes show n — 3i absorption with a maximum around 275 nm ( —201 mol - cm In cyclohexane solution, nitromethane (CH1NOi) is photoreduced to nitrosomethane(CH,NO, but nitroethane under the same conditions gives rise to a nitroso-dimer derived from the solvent CS.47). The latter process is probably initiated by cleavage of the carbon-nitrogen bond in the nitroalkane. In basic solution (when the nitroalkane is converted to a nitronate anion) irradiation can lead to efficient formation of a hydroxamic acid (S.48), and this reaction most likely proceeds through formation of an intermediate three-mem bered cyclic species. 

The product of the reaction of methyl radicals with NO was generally assumed to be nitrosomethane, CH3NO, even before it was found. 

An unexplained feature of the reaction was the observation that added NO inhibits HCN and gives rise to CH3NO2. Separate experiments showed that NO reacted with nitrosomethane to give nitromethane (Levy, he, cit.). This is certainly an unexpected result. 

As carried out industrially, the processes pose problems in almost all their aspects. The catalysts generally operate between 800 and 1100 °C and at very high space velocities (>100 000 h ) with contact times of the order of 10" — 10 s the question arises therefore whether the reactions are wholly surface catalysed, or whether surface initiated gas-phase reactions are important. Since there is a considerable reorganization of atoms in reactants during their conversion to products, the nature of the reaction intermediates has been the subject of considerable speculation over many years. Reaction theories for ammonia oxidation were named, prior to 1960, after the principle intermediate proposed, viz. the imide (NH), nitroxyl (HNO), and hydroxylamine (NH2OH) theories. Similarly, alternative theories for the Andrussow cyanide process have proposed methylene-imine (CH2=NH) and nitrosomethane (CH3.NO) as reaction intermediates. Modern techniques might now reasonably be expected to discriminate amongst these hypotheses. 

Thieno[2,3-c]furan and thieno[2,3-c]pyrrole also behave as thiophene-2,3-quinodimethane equivalents. Thus, intramolecular Diels-Alder reaction of the furan (588) followed by acid-catalyzed dehydration affords the benzo[6]thiophene (589) in good overall yield (Scheme 122) <88TLI 137>. The Diels-Alder reaction of the pyrrole (590) with DMAD followed by oxidation of the resulting adduct (591) affords the benzo[ft]thiophene (592) with loss of nitrosomethane (Scheme 123) <90JOC2446>. 

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