The local structure in liquid methylamine and methylamine–water mixtures

Abstract

Articles you may be interested inHydrogen bonded structure, polarity, molecular motion and frequency fluctuations at liquid-vapor interface of a water-methanol mixture: An ab initio molecular dynamics study Structure, thermodynamics, and dynamics of the liquid/vapor interface of water/dimethylsulfoxide mixtures Molecular dynamics ͑MD͒ computer simulations are carried out on liquid methylamine and on 10 and 30 wt % aqueous solutions of methylamine. The local three-dimensional structure in these liquid systems is investigated using standard one-dimensional radial distribution functions and the fully three-dimensional measure of the local structure around the molecule, spatial distribution functions. Time correlation functions for the linear and angular motion of methylamine in the molecular coordinate system are also explored. From this analysis, a detailed structural picture emerges, revealing local molecular environments in these liquids that are both complex and varied. Hydrogen bond balance is found to play a key role in determining preferred arrangements. Strong hydrogen bonds are formed around the amino group in the pure liquid and in aqueous solution. At the same time, there is a strong hydrophobic association of methyl groups. The hydration structure in aqueous solution is found to be particularly rich, where in addition to the usual H-bonding nearest neighbors in the first hydration shell of the amino group, there are bridging water molecules and a novel type of distinctly non-H-bonding neighbors. The hydration structure in aqueous methylamine solution differs substantially from that found in methanol-water liquid mixtures.

On the structure of prilocaine in aqueous and amphiphilic solutions

“…The somewhat similar hydration of the amine motif in PLC and the ammonium motif in hPLC is consistent with Monte Carlo simulations of these groups in pure water, 44 however here it might be expected that this hydration would be more significantly altered, perhaps being more reduced, given that PLC is highly insoluble in pure water and that there are relatively fewer water molecules present in the methanol/water solution. While it may be that the water molecules that donate hydrogen bonds to the amine group in PLC are less tightly bound compared with amine or ammonium HÁ Á ÁOw hydrogen bonds, as was observed in MD simulations for methylamine in aqueous solution, 45 this does not account for the relatively low solubility of PLC in water given that methylamine is highly water soluble. This also helps to emphasize that it is rather the dehydration of the other sites around PLC which are responsible for its low solubility in water and, perhaps, for its ability to shed water as it crosses the BBB in vivo.…”

On the micro-heterogeneous structure of neat and aqueous propylamine mixtures: A computer simulation study

“…Amines have not been studied by computer simulation as much as alcohols, as can be seen by the scarcely available force fields [17], other than the usual Gromos [18,19] and OPLS [20,21] transferable force fields. Kusalik et al [22] have studied methylamine and aqueous methylamine. Lachet et al [17] have studied a large variety of alkanolamines and their aqueous mixtures, and have proposed a new force field in order to obtain better excess enthalpies.…”

Investigation of the liquid-vapour interface of aqueous methylamine solutions by computer simulation methods

“…Properties of liquid methylamine have also been studied by computer simulation methods several times in the bulk liquid phase. Thus, Kusalik et al investigated the local structure around the methylamine molecules both in its neat liquid phase and aqueous solutions [18]. Kosztolányi et al also investigated the local structure, including hydrogen bonding, in neat liquid methylamine using radial distribution functions and density projections of the neighbouring molecules.…”