N-Nitrosation of Amines by NO₂ and NO:  A Theoretical Study

Abstract

Gas-phase nitrosation of amines implies a nonionic pathway different from the nitrosonium nitrosation via acidification of nitrite. Electronic structure calculations discussed in this work suggest a free radical mechanism, in which NO2 abstracts a hydrogen atom from the nitrogen in primary and secondary amines to form an intermediate complex of an aminyl radical and nitrous acid. The aminyl radical intermediate is then quenched by nitric oxide, leading to the formation of nitrosamine. High-level calculations (CBS-QB3) show that alkyl substitutions on amines can activate the H-abstraction reaction. Thus, while H-abstraction from NH3 was found to exhibit a reaction barrier (DeltaH) of 106 kJ/mol, similar calculations indicate that the corresponding barriers decrease to 72 and 45 kJ/mol for methylamine and dimethylamine, respectively. Heterocyclic secondary amines have also been investigated in a similar manner. The five-membered-ring (5-m-r) amine appears to be the most reactive: pyrrolidine (DeltaH=30 kJ/mol), azetidine (DeltaH=44 kJ/mol), piperidine (DeltaH=44 kJ/mol), and aziridine (DeltaH=74 kJ/mol). The reaction barrier for 1H-pyrrole, an aromatic 5-m-r secondary amine, was found to be 59 kJ/mol. The origin of the high activity for the 5-m-r alkylamine stems from a hydrogen-bond-like interaction between the aminyl radical and the nascent nitrous acid molecule. This theoretical study suggests that, in the presence of nitrogen oxides, the gas-phase nitrosation of secondary amines is feasible.

Mechanism of Nitric Oxide Reactivity and Fluorescence Enhancement of the NO-Specific Probe CuFL1

“…7 and Table 2). The enthalpy of activation (Δ H ‡ = 41 ± 2 kJ/mol) and activation energy ( E a = 43 ± 2 kJ/mol) indicate a relatively low activation barrier for the reaction and are consistent with values obtained from other experimental and theoretical examinations of nitrosation of secondary amines 39–41. The negative entropy of activation (Δ S ‡ = −120 ± 10 J/mol·K) is consistent with an associative nitrosation mechanism.…”

Reactivity of amines with hypochlorous acid: Computational study of steric, electronic, and medium effects

“…3). Also, the order of reactivity for heterocyclic amines follows the increase in the ring size (the similar was found in the case of N‐nitrosation of heterocyclic amines) 43. For example, seven‐membered azepine, having GB = 923.5 kJ mol −1 , is more reactive than four‐membered ring azetidine, which has GB = 908.6 kJ mol −1 .…”

Extraordinary NO2 Removal by the Metal–Organic Framework UiO‐66‐NH2

“…This behavior is supported by atomic ratios calculated from XPS data, where it is shown that nitrogen associated with the amine group is actually reduced compared to the baseline material. The amine group may also be responsible for forming complexes with NO 2 and any NO generated by other reactions, such as interaction with water …”