Amine-ozone adduct

The probable reaction course to the nitroalkane (XI), after the formation of the amine-ozone adduct (Reaction 1), is shown by Reactions 7 to 9 and summed up in Reaction 10. A primary amine oxide would not be expected to be stable and should rearrange to the hydroxylamine (IX, Reaction 7). A similar set of reactions (Reaction 8) should result in the nitrosoalkane (X), which should then be converted to the nitroalkane (XI) as shown in Reaction 9. Evidence for this series of reactions was the observation of the blue color of the nitrosoalkane (X) throughout the ozonation and the demonstration, in separate experiments, that the hydroxylamine (IX) reacts with two mole equivalents of ozone and the nitrosoalkane (X) with one mole equivalent of ozone, each to give the nitroalkane (XI). 

The hterature suggests that more than one mechanism may be operative for a given antiozonant, and that different mechanisms may be appHcable to different types of antiozonants. All of the evidence, however, indicates that the scavenger mechanism is the most important. All antiozonants react with ozone at a much higher rate than does the mbber which they protect. The extremely high reactivity with ozone of/)-phenylenediamines, compared to other amines, is best explained by their unique abiUty to react ftee-tadicaHy. The chemistry of ozone—/)-PDA reactions is known in some detail (30,31). The first step is beheved to be the formation of an ozone—/)-PDA adduct (32), or in some cases a radical ion. Pour competing fates for dissociation of the initial adduct have been described amine oxide formation, side-chain oxidation, nitroxide radical formation, and amino radical formation. 

A-Phenylaziridines may be cleaved to the A-unsubstituted aziridines in good yield with ozone <78TL3ii9). The stable hemiaminal adducts of aziridines with aldehydes may react with amines to give aminals (A-(l-aminoalkyl)aziridines) [Pg.37]

The expected initial reaction between ozone and amines would be an electrophilic ozone attack to give adduct I (Reaction 1) ), A similar adduct has actually been observed in the reaction between the nucleophile triphenylphosphite and ozone (20). It occurred to us that all of the reactions described above could be explained by competing fates... 

In the ozonation of tri-n-butylamine at —40°C. with an ozone-nitrogen stream, 1.2 to 1.6 mole equivalents of ozone were absorbed, and the yields of tri-n-butylamine oxide were 53% from chloroform and 6% from pentane solvents. The other products were the side chain oxidation products described by Henbest and Stratford (II). These results eliminate the possibility that the side chain oxidation is an ozone-initiated autoxidation. The mechanism outlined by Reaction 3 explains nicely both the requirement of ozone itself as the oxidizing agent and the solvent effect observed. Solvents such as chloroform would be expected to solvate the ozone-amine adduct (lb) and make the abstraction of the proton in Reaction 3 difficult. Thus, loss of molecular oxygen to give the amine oxide becomes the major reaction (Reaction 2). In pentane solu-... 

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