Solubility of Water in a Benzene−Cyclohexane Mixture

Abstract

The solubility of a water molecule in a binary mixture of nonpolar cyclohexane and quadrupolar benzene is studied with the ab initio method. A novel self-consistent reaction field theory that properly accounts for benzene quadrupole moments in the continuum solvent framework is used to describe the solvation effects of the solvent mixture. The free energy of transfer from pure cyclohexane to the mixture solvent is obtained with the neglect of nonelectrostatic contributions. A reasonable agreement with experiments indicates that the theoretical method presented here provides a promising approach to electronic structure calculations in quadrupolar solvents and their mixtures with nonpolar solvents.

Quadrupolarizability of Liquid Mixtures

“…The main intention of the present study was to provide a recipe for the formulation of a series of "standard" quadrupolar mixtures with a relatively stable (not varying with the composition) dielectric constant  and known varying quadrupole length LQ. Such standard solvent are necessary [23] to investigate the role of the quadrupolarizability on chemical and physical phenomena such as quadrupolar solvatochromism [12,13], effect of solvent's quadrupole moment on the rate of a reaction [14][15][16], solubility [23] etc. For the purpose of computing LQ, we generalized Onsager's spherical cavity model for mixtures by including explicitly the quadrupoles and the field gradient in the model.…”

“…Moreover, our eqs – provide a recipe for the formulation of a series of “standard” quadrupolar mixtures with a stable (not varying with the composition) dielectric constant ε and known controlled variation of the quadrupolar length L Q . Such standard solvents are appropriate to investigate the role of the quadrupolarizability in such phenomena as quadrupolar solvatochromism, , effect of solvent’s quadrupole moment on the rate of a reaction, − solubility, etc.…”

“…In order to experimentally investigate systematically the effect of the solvent quadrupole moment on the properties of a solute [12][13][14][15][16][17][18][19], it will be beneficial to formulate a set of "standard" solvents or solvent mixtures with permittivity  that is approximately constant but of different LQan idea that belongs to Dorairaj, Jeon and Kim [23]. The mixtures of benzene and cyclohexane is particularly suitable for this aim [23]. Both components are non-polar (intrinsic dipole moment, p0 = 0), and have similar molecular polarizability p [24] and size.…”

“…In order to systematically investigate the effect of the solvent quadrupole moment on the properties of a solute − without the complication from simultaneous change in polarizability, it will be beneficial to formulate a set of “standard” solvents or solvent mixtures with permittivity ε that is approximately constant but of different L Q an idea that belongs to Dorairaj, Jeon, and Kim . The mixtures of benzene and cyclohexane are particularly suitable for this aim .…”

“…In order to systematically investigate the effect of the solvent quadrupole moment on the properties of a solute − without the complication from simultaneous change in polarizability, it will be beneficial to formulate a set of “standard” solvents or solvent mixtures with permittivity ε that is approximately constant but of different L Q an idea that belongs to Dorairaj, Jeon, and Kim . The mixtures of benzene and cyclohexane are particularly suitable for this aim . Benzene has a very large permanent quadrupole moment and large L Q ∈ 1.6–1.8 Å; for cyclohexane, L Q is much lower, probably on the order of 0.5 Å. , On the other hand, both components are nonpolar (intrinsic dipole moment p 0 = 0), and have similar molecular polarizability α p and size.…”