Aldehyde as a potential source of aminol in troposphere: Influence of water and formic acid catalysis on ammonolysis of formaldehyde

Abstract

Formation of 1-aminomethanol in troposphere through the reaction between formaldehyde and ammonia has been investigated by means of electronic structure and chemical kinetics calculations employing CCSD(T)/CBS//MP2/aug-cc-pVTZ level of theory. The process is not favorable under tropospheric conditions due to high reaction barrier (30.4 kcal mol−1) and very low rate coefficient (1.7×10−34 cm3 molecule−1 s−1 at 298 K). As a result, catalytic influence of water (monomer and dimer) and formic acid on the ammonolysis of formaldehyde have also been studied. Formic acid was found to be the most efficient in lowering the activation energy and makes the reaction barrierless. It acts better than the other catalysts in terms of rate coefficient as well (increment in rate coefficient with respect to uncatalyzed channel is by ∼1021 times whereas the same for water dimer and water monomer are by ∼1015 and ∼1011, respectively). Further comparative studies on the efficiencies of catalysts carried out by means of relative rate calculations reveal that formic acid catalyzed channel dominates over the water catalyzed channels at 0 km altitude when concentration of the former is high but water catalyzed channels dominate at higher temperature when formic acid is present in low concentration. On the other hand, the reaction proceeds almost exclusively via formic acid catalyzed channel at higher altitudes in troposphere.