An insight into thermodynamic and association behaviours of cocamidopropyl betaine (CAPB) surfactant in water and water–alcohol mixed media

Abstract

This article presents new experimental data about the conductivity and surface of Cocamidopropyl Betaine (CAPB) surfactant in pure H 2 O and organic-H 2 O mixed solvent (methanol, MeOH; ethanol, EtOH and glycerol, GlyOH) media containing various mole fractions of alcohols over the temperature range 298.15 to 313.15 K, in steps of 5 K using conductometric and surface tension measurements. The experimental data for conductivity and surface tension have been used in order to determine the critical micelle concentration (CMC). It has been observed that the CMC increases with increasing temperature and proportion of alcohol. Moreover, the association constant (K a) of CAPB was also determined, depending on the conductivity data, using the Shedlowsky equation. The study showed that, as the temperature and alcohol ratio increased, the association constant of CAPB decreased. In addition, it was found that the CMC increased with MeOH > EtOH > GlyOH and the association behaviour was observed to be spontaneous. The thermodynamics behaviour of (CAPB) surfactant have been thoroughly assessed from the temperature dependence of the micellization and association constants. In all media studied, densities and refractive indices of CAPB were also measured under atmospheric pressure, in the solvents used at T = (298.15 K). The molal volume was estimated based on the density data and some additionally parameters such as molar refraction and the polarizability were also estimated and discussed depending on the refractive index values. These parameters have been utilized to comprehend the association and solvation behaviour of the CAPB surfactant.

Solvolysis Thermodynamic Parameters of Phenyl Hydrazine Hydrochloride

“…This was subsequently confirmed by the positive values of the free energy change and the activation energy of the solvolysis process. [12,17,[19][20][21][22] The positive values of the free energy change ( ) and the standard enthalpy change ( ), indicate that the solvolysis process is non spontaneous endothermic process. [12,17,[19][20][21].…”

“…[12,17,[19][20][21][22] The positive values of the free energy change ( ) and the standard enthalpy change ( ), indicate that the solvolysis process is non spontaneous endothermic process. [12,17,[19][20][21]. The solvolysis constant is increase as the alcohol percentage increase from 30-100%.…”

“…The results listed in Table 5 indicated that the solvolysis constant increase as the temperature degree increase as subsequently confirmed by the positive values of the free energy change ( ), and the activation energy of the solvolysis process. [12,17,[19][20][21] The positive values of the free energy change ( ) and the standard enthalpy change ( ), indicate that the solvolysis process is non spontaneous endothermic process. [12,17,[19][20][21] The solvolysis constant decrease as the ethanol added to water.…”

“…[12,17,[19][20][21] The positive values of the free energy change ( ) and the standard enthalpy change ( ), indicate that the solvolysis process is non spontaneous endothermic process. [12,17,[19][20][21] The solvolysis constant decrease as the ethanol added to water. This may be due to the lower dielectric constant and lower dipole moment of EtOH-H 2 O mixed solvent than that of H 2 O.…”

“…[4,[6][7][8][9][10][11][12] Several methods, including conductometric, pH titration, [5,13,14] spectrophotometry, [15][16][17] and ion-exclusion based chromatographic [9,18] have been used to determine the hydrolytic rate of several compounds. [12,17,[19][20][21] As far as we know, the solvolysis rate of hydrazine and its derivatives have not been studied, especially for hydrazine hydrochloride salts.…”