Adsorption of cycloalkane and cyclopentanealkyl acids at the air/water interface

Abstract

Surface tensions of aqueous solutions of cyclopropane, cyclobutane, cyclopentane, and cycloheptane carboxylic acids, and of cyclopentaneacetic and cyclopentanepropionic acids were measured at 25 °C by the drop volume method. The Traube constants for calculation of standard free energies of adsorption were estimated from second and third degree polynomial least-squares analyses, from nonlinear least-squares analysis using the Szyszkowsky equation, and graphically.The standard free energies of adsorption at the air/solution interface of cycloalkane and cycloalkanealkyl carboxylic acids are less negative than those of the corresponding straight chain acids, but not by a constant amount; the standard free energy of the CH2 group in a cycloalkane ring is −2.5 kJ mol−1 as compared to a value of −3.3 kJ mol−1 for straight chain acids.