On the hydrophobic hydration, solvation and interface: A thought essay (I)

This essay covers aspects concerning with the hydrophobic hydration of apolar gas (H-2, He, Ne, N-2, O-2, Ar, CH4, C2H6, C3H8, n-C4H10 and i-C4H10), solubilities in water and hexadecane, interfacial tensions of water/gases, hexadecane/gases and n-alkane (C7-C18)/N-2 and O-2 interface at 298 K. The main results are: (1) Two water layers of hydration should be taken into account. 1st layer closest to an apolar molecule is hot ice or ordered gas and independent to 2nd layer. Water dipoles orderly, dramatically and endlessly rotate and create a negative electric field, in turn electro-freeze 2nd layer. (2) Entropic change of H+ partition between 2nd layer and bulk water leads to the ionization of water. (3) Interfacial tension and internal pressure of 2nd layer caused by electric potential are -13.9 mJ/m(2) and -54 MPa, respectively. (4) Thermodynamic process for solvation: (i) isothermally compressing gas to the solid state to take in all the kinetic energy of gas for creating a cavity with 4 free HBs; (ii) mixing the hydrates (solvated entities) with water (alkane) as mixing of ideal gas. (5) Gas collides with surface to create the crystalline foam consisting of 4 layers of hydrates or solvated entities. The solubilities of gases, the interfacial tension and internal pressure of water (alkane)/gas interface are calculated with quite appraisable results. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

This essay discusses the hydrophobic hydration of apolar gases, solubilities in water and hexadecane, and interfacial tensions at various interfaces. The main findings include the existence of two water layers of hydration, the ionization of water due to entropic changes, and the calculations of interfacial tensions and internal pressures.