Time-dependent vibrational spectral analysis of first principles trajectory of methylamine with wavelet transform

Biswas, Sohag; Mallik, Bhabani S.

doi:10.1039/c7cp00412e

“…Other studies have used less stringent criteria with cut-off angles of 45 • 77 or only employed distance-based criteria between the N-H group and surrounding water molecules. 68,[78][79][80] In the present study, our RDF calculations show that the dimethylamine molecule makes a single hydrogen bond with water molecules via the N terminal group but makes less than one hydrogen bond via the H atom in the N-H group with neighboring water molecules. Due to the variation in the number of hydrogen-bonds formed by dimethylamine with the surrounding water, we have only adopted a distancebased criteria to allow more flexibility in the calculation of the hydrogen-bond autocorrelation function.…”

Section: Hydrogen Bond Dynamicssupporting

confidence: 48%

Ab Initio Metadynamics Calculations of Dimethylamine for Probing pKb Variations in Bulk vs. Surface Environments

Biswas¹,

Kwon²,

Barsanti³

et al. 2020

Preprint

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The basicity constant, or pKb, is an intrinsic physical property of bases that gives a measure of its proton affinity in macroscopic environments. While the pKb is typically defined in reference to the bulk aqueous phase, several studies have suggested that this value can differ significantly at the air-water interface (which can have significant ramifications for particle surface chemistry and aerosol growth modeling). To provide mechanistic insight into surface proton affinity, we carried out ab initio metadynamics calculations to (1) explore the free-energy profile of dimethylamine and (2) provide reasonable estimates of the pKb value in different solvent environments. We find that the free-energy profiles obtained with our metadynamics calculations show a dramatic variation, with interfacial aqueous dimethylamine pKb values being significantly lower than in the bulk aqueous environment. Furthermore, our metadynamics calculations indicate that these variations are due to reduced hydrogen bonding at the air-water surface. Taken together, our quantum mechanical metadynamics calculations show that the reactivity of dimethylamine is surprisingly complex, leading to pKb variations that critically depend on the different atomic interactions occurring at the microscopic molecular level.

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“…Other studies have used less stringent criteria with cut-off angles of 45 • 75 or only employed distance-based criteria between the N-H group and surrounding water molecules. 66,[76][77][78] In the present study, our RDF calculations show that the dimethylamine molecule makes a single hydrogen bond with water molecules via the N terminal group but makes less than one hydrogen bond via the H atom in the N-H group with neighboring water molecules. Due to the variation in the number of hydrogen-bonds formed by dimethylamine with the surrounding water, we have only adopted a distancebased criteria to allow more flexibility in the calculation of the hydrogen-bond autocorrelation function.…”

Section: Hydrogen Bond Dynamicssupporting

confidence: 48%

Ab Initio Metadynamics Calculations of Dimethylamine for Probing pKb Variations in Bulk vs. Surface Environments

Biswas¹,

Kwon²,

Barsanti³

et al. 2020

Preprint

Self Cite

0

View full text Add to dashboard Cite

The basicity constant, or pKb, is an intrinsic physical property of bases that gives a measure of its proton affinity in macroscopic environments. While the pKb is typically defined in reference to the bulk aqueous phase, several studies have suggested that this value can differ significantly at the air-water interface (which can have significant ramifications for particle surface chemistry and aerosol growth modeling). To provide mechanistic insight into surface proton affinity, we carried out ab initio metadynamics calculations to (1) explore the free-energy profile of dimethylamine and (2) provide reasonable estimates of the pKb value in different solvent environments. We find that the free-energy profiles obtained with our metadynamics calculations show a dramatic variation, with interfacial aqueous dimethylamine pKb values being significantly lower than in the bulk aqueous environment. Furthermore, our metadynamics calculations indicate that these variations are due to reduced hydrogen bonding at the air-water surface. Taken together, our quantum mechanical metadynamics calculations show that the reactivity of dimethylamine is surprisingly complex, leading to pKb variations that critically depend on the different atomic interactions occurring at the microscopic molecular level.

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“…Recently, Biswas and Mallik studied the bulk phase orientational preferences of the methylamine molecules in neat methylamine [20] as well as in its aqueous solution [21] at ambient conditions by first principles molecular dynamics simulations using dispersion corrected density functional (BLYP-D). Computer simulation studies of the behaviour of methylamine at aqueous interfaces are, however, rather scarce.…”

Section: Introductionmentioning

confidence: 99%

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

Horváth

¹

,

Fábián

²

,

Szőri

³

et al. 2019

Journal of Molecular Liquids

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Molecular dynamics simulations of the liquid-vapour interface of water-methylamine mixtures of eight different compositions, including neat water, are performed on the canonical (N,V,T) ensemble at 280 K. The molecules constituting the first three individual molecular layers beneath the liquid surface are identified by the Identification of the Truly Interfacial Molecules (ITIM) method. The results indicate that methylamine molecules are strongly adsorbed in the first, and somewhat depleted in the second molecular layer, while the composition of the third layer agrees well with that of the bulk liquid phase. On the other hand, methylamine molecules do not show considerable self-association within the surface layer. The orientational preferences of the methylamine molecules at the liquid surface are clearly governed by the requirement of maximizing their hydrogen bonding interaction. As a consequence, methylamine molecules point by their apolar CH3 group straight to the vapour, while by the potential hydrogen bonding directions of the NH2 group flatly to the liquid phase. Further, within the surface layer, methylamine molecules stay, on average, noticeably farther from the bulk liquid phase than waters. Increasing methylamine mole fraction leads to the gradual breaking up of the lateral percolating H-bonding network of the surface molecules. Finally, methylamine molecules accelerate, while water molecules slow down the exchange of both species between the liquid surface and the bulk liquid phase. Further, methylamine molecules slow down the lateral diffusion of each other, and even prevent water molecules from showing noticeable lateral diffusion within the surface layer. The reason for this latter effect is that the mean residence time of the water molecules at the liquid surface becomes considerably shorter than the characteristic time of their lateral diffusion in the presence of methylamine.

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Time-dependent vibrational spectral analysis of first principles trajectory of methylamine with wavelet transform

Cited by 21 publications

References 74 publications

Ab Initio Metadynamics Calculations of Dimethylamine for Probing pKb Variations in Bulk vs. Surface Environments

Ab Initio Metadynamics Calculations of Dimethylamine for Probing pKb Variations in Bulk vs. Surface Environments

Ab Initio Metadynamics Calculations of Dimethylamine for Probing pKb Variations in Bulk vs. Surface Environments

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

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