start-ver=1.4 cd-journal=joma no-vol=25 cd-vols= no-issue=45 article-no= start-page=31107 end-page=31117 dt-received= dt-revised= dt-accepted= dt-pub-year=2023 dt-pub=2023 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Solvation free energies of alcohols in water: temperature and pressure dependences en-subtitle= kn-subtitle= en-abstract= kn-abstract=Solvation free energies μ* of amphiphilic species, methanol and 1,2-hexanediol, are obtained as a function of temperature or pressure based on molecular dynamics simulations combined with efficient free-energy calculation methods. In general, μ* of an amphiphile can be divided into Image ID:d3cp03799a-t1.gif and Image ID:d3cp03799a-t2.gif, the nonpolar and electrostatic contributions, and the former is further divided into Image ID:d3cp03799a-t3.gif and Image ID:d3cp03799a-t4.gif which are the work of cavity formation process and the free energy change due to weak, attractive interactions between the solute molecule and surrounding solvent molecules. We demonstrate that μ* of the two amphiphilic solutes can be obtained accurately using a perturbation combining method, which relies on the exact expressions for Image ID:d3cp03799a-t5.gif and Image ID:d3cp03799a-t6.gif and requires no simulations of intermediate systems between the solute with strong, repulsive interactions and the solute with the van der Waals and electrostatic interactions. The decomposition of μ* gives us several physical insights including that μ* is an increasing function of T due to Image ID:d3cp03799a-t7.gif, that the contributions of hydrophilic groups to the temperature dependence of μ* are additive, and that the contribution of the van der Waals attraction to the solvation volume is greater than that of the electrostatic interactions. en-copyright= kn-copyright= en-aut-name=TairaAoi en-aut-sei=Taira en-aut-mei=Aoi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=OkamotoRyuichi en-aut-sei=Okamoto en-aut-mei=Ryuichi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=SumiTomonari en-aut-sei=Sumi en-aut-mei=Tomonari kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=KogaKenichiro en-aut-sei=Koga en-aut-mei=Kenichiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= affil-num=1 en-affil=Department of Chemistry, Faculty of Science, Okayama University kn-affil= affil-num=2 en-affil=Graduate School of Information Science, University of Hyogo kn-affil= affil-num=3 en-affil=Department of Chemistry, Faculty of Science, Okayama University kn-affil= affil-num=4 en-affil=Department of Chemistry, Faculty of Science, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=156 cd-vols= no-issue=22 article-no= start-page=221104 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2022 dt-pub=20220614 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Osmotic second virial coefficients for hydrophobic interactions as a function of solute size en-subtitle= kn-subtitle= en-abstract= kn-abstract=To gain quantitative insight into how the overall strength of the hydrophobic interaction varies with the molecular size, we calculate osmotic second virial coefficients B for hydrophobic spherical molecules of different diameters σ in water based on molecular simulation with corrections to the finite-size and finite-concentration effects. It is shown that B (<0) changes by two orders of magnitude greater as σ increases twofold and its solute-size dependence is best fit by a power law B ∝ σ α with the exponent α ≃ 6, which contrasts with the cubic power law that the second virial coefficients of gases obey. It is also found that values of B for the solutes in a nonpolar solvent are positive but they obey the same power law as in water. A thermodynamic identity for B derived earlier [K. Koga, V. Holten, and B. Widom, J. Phys. Chem. B 119, 13391 (2015)] indicates that if B is asymptotically proportional to a power of σ, the exponent α must be equal to or greater than 6. en-copyright= kn-copyright= en-aut-name=NaitoHidefumi en-aut-sei=Naito en-aut-mei=Hidefumi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=OkamotoRyuichi en-aut-sei=Okamoto en-aut-mei=Ryuichi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=SumiTomonari en-aut-sei=Sumi en-aut-mei=Tomonari kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=KogaKenichiro en-aut-sei=Koga en-aut-mei=Kenichiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= affil-num=1 en-affil=Department of Chemistry, Faculty of Science, Okayama University kn-affil= affil-num=2 en-affil=Department of Chemistry, Faculty of Science, Okayama University kn-affil= affil-num=3 en-affil=Department of Chemistry, Faculty of Science, Okayama University kn-affil= affil-num=4 en-affil=Department of Chemistry, Faculty of Science, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=125 cd-vols= no-issue=46 article-no= start-page=12820 end-page=12831 dt-received= dt-revised= dt-accepted= dt-pub-year=2021 dt-pub=20211110 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Theory of Gas Solubility and Hydrophobic Interaction in Aqueous Electrolyte Solutions en-subtitle= kn-subtitle= en-abstract= kn-abstract=Ion-specific effects on the solubility of nonpolar solutes and on the solute–solute hydrophobic interaction in aqueous electrolyte solutions are studied on the basis of a continuum theory that incorporates the excluded volume of the molecules using the four-component (water, cations, anions, and solutes) Boublı́k–Mansoori–Carnahan–Starling–Leland model and ion hydration (electrostriction) using the Born model. We examine how the ordering of ions in the salt effect on the solubility as measured by the Sechenov coefficient KS changes with varying sizes of ions and solutes. Our calculation reproduces the general trend of experimentally measured KS and also provides insight into the irregular behavior of KS for lithium ion. The correlation between KS and the salt effect on the hydrophobic interaction that has been pointed out earlier is accounted for by an explicit connection between KS and the salt-enhanced-association coefficient CI in the expansion of the second osmotic virial coefficient B(ns) = B(0) – CIns + ··· in powers of the salt density ns at fixed pressure and temperature. The quadratic relation is derived for ions and solutes that are not very large. en-copyright= kn-copyright= en-aut-name=OkamotoRyuichi en-aut-sei=Okamoto en-aut-mei=Ryuichi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=KogaKenichiro en-aut-sei=Koga en-aut-mei=Kenichiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=2 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= END