Local Structure of DMF–Water Mixtures, as Seen from Computer Simulations and Voronoi Analysis

Abstract

Molecular dynamics simulations of mixtures of N,N-dimethylformamide (DMF) with water of various compositions, covering the entire composition range, are performed on the canonical (N,V,T) ensemble. The local structure of the mixtures is analyzed in terms of radial distribution functions and the contributions of the first five neighbors to them, various order parameters of the water molecules around each other, and properties of the Voronoi polyhedra of the molecules. The analyses lead to the following main conclusions. The two molecules are mixing with each other even on the molecular scale; however, small self-aggregates of both components persist even at their small mole fraction values. In particular, water–water H-bonds exist in the entire composition range, while water clusters larger than 3 and 2 molecules disappear above the DMF mole fraction values of about 0.7 and 0.9, respectively. The O atoms of the DMF molecules can well replace water O atoms in the hydrogen-bonding network. Further, the H-bonding structure is enhanced by the presence of the hydrophobic CH3 groups of the DMF molecules. On the other hand, the H-bonding network of the molecules gradually breaks down upon the addition of DMF to the system due to the lack of H-donating groups of the DMF molecules. Finally, in neat DMF, the molecules form weak, CH-donated H-bonds with each other; however, these H-bonds disappear upon the addition of water due to the increasing competition with the considerably stronger OH-donated H-bonds DMF can form with the water molecules.

Surface Properties of N,N-Dimethylformamide–Water Mixtures, As Seen from Computer Simulations

“…The resulting distributions together with their best fits by eq are shown in Figure . The obtained distributions exhibit rather similar behavior to what has previously been seen in the bulk liquid phase of these systems . Thus, the peak of the P ( A ) distribution shifts smoothly from the position characteristic to neat water to that of neat DMF with increasing x DMF , indicating that the two molecules mix with each other on the molecular scale even at the liquid surface.…”

Surface Properties of N,N-Dimethylformamide–Water Mixtures, As Seen from Computer Simulations

“…The resulting distributions together with their best fits by eq are shown in Figure . The obtained distributions exhibit rather similar behavior to what has previously been seen in the bulk liquid phase of these systems . Thus, the peak of the P ( A ) distribution shifts smoothly from the position characteristic to neat water to that of neat DMF with increasing x DMF , indicating that the two molecules mix with each other on the molecular scale even at the liquid surface.…”

Energetics of acid catalyzed biomass reactions: how and why does the solvent model matter?

“…Still, the addition of DMF gradually disrupts the highly interconnected H-bonds network due to the lack of existing H-donating groups in the aprotic solvent molecules. 91 Due to the structural similarities between DMF and DMSO molecules, we suggest that the H-bonds water network also breaks down by adding DMSO in a similar fashion. These changes in the water interconnected H-bonds network by the addition of DMSO results in the loss of the ability of extensive water molecules' network to adapt almost instantaneously during and after the protonation reaction, and the fewer water molecules (now interacting with DMSO too) need to undergo a more extensive molecular rearrangement due to the hindrance caused by the DMSO molecules.…”

Voronoi Tessellation as a Tool for Predicting the Formation of Deep Eutectic Solvents

“…The results just illustrated can also be obtained through another approach, widely adopted by Idrissi, ,, namely, the analysis of the long-tail decay of the logarithm of the volume distribution. Such a slow decay has been proven to act as a marker for the presence of an inhomogeneous environment .…”

Surface Properties of N,N-Dimethylformamide–Water Mixtures, As Seen from Computer Simulations

“…The resulting distributions together with their best fits by eq are shown in Figure . The obtained distributions exhibit rather similar behavior to what has previously been seen in the bulk liquid phase of these systems . Thus, the peak of the P ( A ) distribution shifts smoothly from the position characteristic to neat water to that of neat DMF with increasing x DMF , indicating that the two molecules mix with each other on the molecular scale even at the liquid surface.…”

Energetics of acid catalyzed biomass reactions: how and why does the solvent model matter?

“…Still, the addition of DMF gradually disrupts the highly interconnected H-bonds network due to the lack of existing H-donating groups in the aprotic solvent molecules. 91 Due to the structural similarities between DMF and DMSO molecules, we suggest that the H-bonds water network also breaks down by adding DMSO in a similar fashion. These changes in the water interconnected H-bonds network by the addition of DMSO results in the loss of the ability of extensive water molecules' network to adapt almost instantaneously during and after the protonation reaction, and the fewer water molecules (now interacting with DMSO too) need to undergo a more extensive molecular rearrangement due to the hindrance caused by the DMSO molecules.…”

Voronoi Tessellation as a Tool for Predicting the Formation of Deep Eutectic Solvents

“…The results just illustrated can also be obtained through another approach, widely adopted by Idrissi, ,, namely, the analysis of the long-tail decay of the logarithm of the volume distribution. Such a slow decay has been proven to act as a marker for the presence of an inhomogeneous environment .…”

Surface Properties of N,N-Dimethylformamide–Water Mixtures, As Seen from Computer Simulations

“…The resulting distributions together with their best fits by eq are shown in Figure . The obtained distributions exhibit rather similar behavior to what has previously been seen in the bulk liquid phase of these systems . Thus, the peak of the P ( A ) distribution shifts smoothly from the position characteristic to neat water to that of neat DMF with increasing x DMF , indicating that the two molecules mix with each other on the molecular scale even at the liquid surface.…”

Energetics of acid catalyzed biomass reactions: how and why does the solvent model matter?

“…Still, the addition of DMF gradually disrupts the highly interconnected H-bonds network due to the lack of existing H-donating groups in the aprotic solvent molecules. 91 Due to the structural similarities between DMF and DMSO molecules, we suggest that the H-bonds water network also breaks down by adding DMSO in a similar fashion. These changes in the water interconnected H-bonds network by the addition of DMSO results in the loss of the ability of extensive water molecules' network to adapt almost instantaneously during and after the protonation reaction, and the fewer water molecules (now interacting with DMSO too) need to undergo a more extensive molecular rearrangement due to the hindrance caused by the DMSO molecules.…”

Voronoi Tessellation as a Tool for Predicting the Formation of Deep Eutectic Solvents

“…The results just illustrated can also be obtained through another approach, widely adopted by Idrissi, ,, namely, the analysis of the long-tail decay of the logarithm of the volume distribution. Such a slow decay has been proven to act as a marker for the presence of an inhomogeneous environment .…”