Condensation of Aniline and o-Hydroxyaniline with 1,2-Dibromoethane

Positively and Negatively Hydrated Counterions in Molecular Dynamics Simulations of DNA Double Helix

“…The obtained results (Table 2) show that the values of 𝑑𝐸 are positive for all counterions: 2.15 kcal/mol, 0.91 kcal/mol, 0.34 kcal/mol for Na + , K + , and Cs + counterions, respectively. At the same time, the experimental data [14] show that, among the considered counterions, only a sodium ion has the positive difference of the potential barriers 𝑑𝐸 = 0.25 kcal/mol, and it is much lower than in the simulations. The potassium and cesium ions have a negative difference of the potential barriers 𝑑𝐸 = −0.25 kcal/mol and 𝑑𝐸 = = −0.33 kcal/mol, respectively [14].…”

“…At the same time, the experimental data [14] show that, among the considered counterions, only a sodium ion has the positive difference of the potential barriers 𝑑𝐸 = 0.25 kcal/mol, and it is much lower than in the simulations. The potassium and cesium ions have a negative difference of the potential barriers 𝑑𝐸 = −0.25 kcal/mol and 𝑑𝐸 = = −0.33 kcal/mol, respectively [14]. That is why they are negatively hydrated.…”

“…The determined potentials of mean force allow us to estimate the residence time 𝜏 for water molecules using an equation of the Arrhenius type [14]. In the present work, this equation is presented in the following form:…”

“…Depending on the structure organization of water molecules, the ions are usually classified into the positively hydrated and the negatively hydrated ones [14]. In the case of positively hydrated ions (Li + , Na + , and Mg 2+ ), the water molecules in the hydration shells are highly ordered, and the mean residence time of the molecule in the ion's hydration shell is much longer than that in the bulk solution [14]. Therefore, these ions are also known as the structure-making ions [15].…”

“…Therefore, these ions are also known as the structure-making ions [15]. In the case of negatively hydrated ions (K + , Rb + , and Cs + ), the mean residence time of water molecules near the ion is shorter than that in the bulk [14], and the structure of the hydration shell is more friable than that of pure liquid water. Therefore, these ions are also known as the structure-breaking ions [15].…”