The Effect of Alkyl Groups with Structural Isomerism on the Hydrophobic Hydration

Kumiko MIKI*, Isao YAMAKAWA and Toyohiko NAKAJIMA

Department of Liberal Arts and Basic Science, College of Industrial Technology, Nihon University; 2-11-1 Shinei-cho, Narashino-shi 275-8576 Japan

The viscosities and the densities of the aqueous solutions of alkanols and sodium monocarboxylates with straight and branched carbon chain (with 1--4 carbon atoms) were measured at 25 °C. The viscosity B-coefficients of Jones-Dole's equation and the limiting partial molar volumes, , were determined. The molar volumes, VB, was calculated from Eq. 4. VB is the value that represents volume of solutes with interacting water.
The change in with -H→-CH3 substitution were not considerable in the case of the straight chain or in the case of the branched chain (Scheme 2). However, the change in VB with -H→-CH3 substitution in the case of the the branched chain was much larger than that in the case of the straight chain (Scheme 1).
Therefore the hydration structure, which was suggested by the change in VB| with -H→-CH3 substitution in the case of the branched chain was formed stronger than that in the case of the straight chain (Scheme 3 and Scheme 4). This fact was supported by the values of hydration entropy (Scheme 5).
These hydrophobic hydration structure-making properties were considered to have caused the differences in the solubilities among butyl alcohol isomers in water.


[Contents (In Japanese) ] [Contents (In English) ]