Stability of Hydrated Methylamine: Structural Characteristics and H₂N···H–O Hydrogen Bonds

Methylamine is the simplest aliphatic amine found in human urine, blood, and tissues. It is thought to play a significant part in central nervous system disturbances observed during renal and hepatic disease. In this work we have investigated the methylamine hydration clusters using a basin hopping (BH) algorithm with the density functional theory (DFT). The results presented herein yield a detailed understanding of the structure and stability for a system consisting of one methylamine molecule and up to seven waters: the most stable geometries arise from a fusion of tetramer or pentamer rings; by the geometrical parameters and topological parameters analysis, the strengths of the H₂N···H–O hydrogen bonds of the global minima increase as the sizes of clusters increase, except for <i>n</i> = 5 where there is a slight fluctuation. This work may shed light on the form mechanism of methylamine existing in organisms and the hydration structures of larger molecules containing amino functional groups and their interaction with the water molecules nearby

Properties and Atmospheric Implication of Methylamine–Sulfuric Acid–Water Clusters

The presence of amines can increase aerosol formation rates. Most studies have been devoted to dimethylamine as the representative of amine; however, there have been a few works devoted to methylamine. In this study, theoretical calculations are performed on CH₃NH₂(H₂SO₄)_<i>m</i>(H₂O)_<i>n</i> (<i>m</i> = 0–3, <i>n</i> = 0–3) clusters. In addition to the structures and energetics, we focused on determining the following characteristics: (1) the growth mechanism, (2) the hydrate distributions and the influences of humidity and temperature, (3) Rayleigh scattering properties. We explored the cluster growth mechanism from a thermodynamics aspect by calculating the Gibbs free energy of adding a water or sulfuric acid molecule step by step at three atmospherically relevant temperatures. The relative ease of the reaction at each step is discussed. From the analysis of hydrate distributions, we find that CH₃NH₂(H₂SO₄)­(H₂O)₂, CH₃NH₂(H₂SO₄)₂, and CH₃NH₂(H₂SO₄)₃ are most likely to exist in the atmosphere. The general trend of hydration in all cases is more extensive with the growing relative humidity (RH), whereas the distributions do not significantly change with the temperature. Analysis of the Rayleigh scattering properties showed that both H₂SO₄ and H₂O molecules could increase the Rayleigh scattering intensities and isotropic mean polarizabilities, with greater influence by the sulfuric acid molecules. This work sheds light on the mechanism for further research on new particle formation (NPF) containing methylamine in the atmosphere