Amine nitration and nitrosation by gaseous nitrogen dioxide

Area of Science:

• Organic Chemistry
• Environmental Chemistry
• Chemical Kinetics

Background:

• Nitrogen dioxide (NO2) is a key atmospheric pollutant.
• Amines are ubiquitous in biological and environmental systems.
• Understanding the reaction mechanisms of NO2 with amines is crucial for assessing environmental and health impacts.

Purpose of the Study:

• To investigate the reaction products of N-methylaniline and heterocyclic amines with gaseous NO2.
• To elucidate the reaction mechanisms of N-nitrosation and N-nitration.
• To determine the influence of NO2 concentration on reaction pathways.

Main Methods:

• Reaction of N-methylaniline and heterocyclic amines in solution with varying concentrations of gaseous NO2.
• Analysis of reaction products, including N-nitroso and N-nitro compounds.

Main Results:

• Reaction with high NO2 concentrations yielded ring- and N-nitro products, alongside N-methyl-N-nitrosoaniline.
• Lower NO2 concentrations with heterocyclic amines produced significant N-nitrosamines and higher N-nitramine yields.
• Evidence suggests N-nitrosation proceeds via an ON-ONO2 dimer, while N-nitration may involve a free-radical mechanism.

Conclusions:

• The concentration of gaseous NO2 significantly influences the reaction pathways with amines.
• Distinct mechanisms are proposed for N-nitrosation and N-nitration.
• These findings contribute to understanding the environmental fate and reactivity of nitrogen dioxide.