Free energy of mixing of pyridine and its methyl-substituted derivatives with water, As seen from computer simulations

Mária Darvas, P. Jedlovszky, G. Jancsó

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Abstract

The free energies of mixing of pyridine, 2-methylpyridine, and 2,6-dimethylpyridine with water have been calculated at 298 K for systems containing 1, 5, and 50 mol % pyridine or its derivative by the method of thermodynamic integration. The obtained results show that the trend of the free energy of mixing of these compounds with water, observed previously at infinite dilution, clearly vanishes at 1 mol % and reverses at higher pyridine concentrations. Thus, in the 5 and 50 mol % systems, the free energy of mixing increases with increasing number of methyl groups. A similar trend is observed for the entropie component of the free energy of mixing at any composition, indicating that, above 1 mol % pyridine content, the entropie term becomes dominant and determines the order of the free energies of mixing of these compounds with water. The fact that this order is in clear accordance with the experimentally observed order of the ease of miscibility of these compounds with water at concentrations above 1 mol % suggests that the entropy of mixing plays a decisive role in the mixing behavior of methyl-substituted pyridines with water.

Original languageEnglish
Pages (from-to)7615-7620
Number of pages6
JournalJournal of Physical Chemistry B
Volume113
Issue number21
DOIs
Publication statusPublished - May 28 2009

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Pyridine
Free energy
pyridines
computerized simulation
free energy
Derivatives
Water
Computer simulation
water
Pyridines
trends
pyridine
Dilution
dilution
Entropy
solubility
Solubility
Thermodynamics
entropy
thermodynamics

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Materials Chemistry
  • Surfaces, Coatings and Films

Cite this

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title = "Free energy of mixing of pyridine and its methyl-substituted derivatives with water, As seen from computer simulations",
abstract = "The free energies of mixing of pyridine, 2-methylpyridine, and 2,6-dimethylpyridine with water have been calculated at 298 K for systems containing 1, 5, and 50 mol {\%} pyridine or its derivative by the method of thermodynamic integration. The obtained results show that the trend of the free energy of mixing of these compounds with water, observed previously at infinite dilution, clearly vanishes at 1 mol {\%} and reverses at higher pyridine concentrations. Thus, in the 5 and 50 mol {\%} systems, the free energy of mixing increases with increasing number of methyl groups. A similar trend is observed for the entropie component of the free energy of mixing at any composition, indicating that, above 1 mol {\%} pyridine content, the entropie term becomes dominant and determines the order of the free energies of mixing of these compounds with water. The fact that this order is in clear accordance with the experimentally observed order of the ease of miscibility of these compounds with water at concentrations above 1 mol {\%} suggests that the entropy of mixing plays a decisive role in the mixing behavior of methyl-substituted pyridines with water.",
author = "M{\'a}ria Darvas and P. Jedlovszky and G. Jancs{\'o}",
year = "2009",
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TY - JOUR

T1 - Free energy of mixing of pyridine and its methyl-substituted derivatives with water, As seen from computer simulations

AU - Darvas, Mária

AU - Jedlovszky, P.

AU - Jancsó, G.

PY - 2009/5/28

Y1 - 2009/5/28

N2 - The free energies of mixing of pyridine, 2-methylpyridine, and 2,6-dimethylpyridine with water have been calculated at 298 K for systems containing 1, 5, and 50 mol % pyridine or its derivative by the method of thermodynamic integration. The obtained results show that the trend of the free energy of mixing of these compounds with water, observed previously at infinite dilution, clearly vanishes at 1 mol % and reverses at higher pyridine concentrations. Thus, in the 5 and 50 mol % systems, the free energy of mixing increases with increasing number of methyl groups. A similar trend is observed for the entropie component of the free energy of mixing at any composition, indicating that, above 1 mol % pyridine content, the entropie term becomes dominant and determines the order of the free energies of mixing of these compounds with water. The fact that this order is in clear accordance with the experimentally observed order of the ease of miscibility of these compounds with water at concentrations above 1 mol % suggests that the entropy of mixing plays a decisive role in the mixing behavior of methyl-substituted pyridines with water.

AB - The free energies of mixing of pyridine, 2-methylpyridine, and 2,6-dimethylpyridine with water have been calculated at 298 K for systems containing 1, 5, and 50 mol % pyridine or its derivative by the method of thermodynamic integration. The obtained results show that the trend of the free energy of mixing of these compounds with water, observed previously at infinite dilution, clearly vanishes at 1 mol % and reverses at higher pyridine concentrations. Thus, in the 5 and 50 mol % systems, the free energy of mixing increases with increasing number of methyl groups. A similar trend is observed for the entropie component of the free energy of mixing at any composition, indicating that, above 1 mol % pyridine content, the entropie term becomes dominant and determines the order of the free energies of mixing of these compounds with water. The fact that this order is in clear accordance with the experimentally observed order of the ease of miscibility of these compounds with water at concentrations above 1 mol % suggests that the entropy of mixing plays a decisive role in the mixing behavior of methyl-substituted pyridines with water.

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