A systematic theoretical study of imines formation from the atmospheric reactions of RnNH2−n with O2 and NO2 (R = CH3 and CH3CH2; n = 1 and 2)

The atmospheric reactions of alkylamino radicals, R1R2N, with O2 and NO2 were studied by theoretical methods to elucidate the possible pathways to imine formation at the atmospheric conditions. The calculations show that all relevant routes proceed via initial additions to the nitrogen atom of the amino radical, R1R2N–NO2, R1R2N–ONO and R1R2N–OO that then may undergo dissociation via five-center-ring transition states resulting in imines and HONO or HO2. The rate coefficient for amino radical reaction with O2 is shown to be several orders of magnitude smaller than the corresponding reaction with NO2. N-nitro amines are the major product in secondary amino radical reactions with NO2. For primary amino radical reactions with NO2 the amounts of N-nitro amines and imines will depend upon pressure and chain length. Results from TDDFT studies of N-nitro and N-nitrooxy amine photo stability indicate fast photolysis of N-nitrooxy amines at atmospheric conditions.

► The atmospheric formation of imines from RnNH2−n + NO2/O2 reactions were studied theoretically.
► The reaction starts from the addition to form RNOO, and then undergo dissociation to imines.
► The dominant product with NO2 reaction is nitroamines.
► Nitroamines are difficult to photolyze in the sunlight.