QUANTUM-CHEMICAL ANALYSIS OF DIMERIZATION THERMODYNAMICS FOR CARBOXYLIC ACIDS AND ALIPHATIC AMINES AT THE AIR/WATER INTERFACE

Abstract

In the frameworks of the quantum-chemical semiempiric PM3 method the thermodynamic parameters of the formation and dimerization processes are calculated for aliphatic amines CnH2n+1NH2 and carboxylic acids CnH2n+1COOH (n = 6-16). It was found that the spontaneous dimerization threshold for mixed associates of surfactants is carbon atoms in the 18-19 chain at 298 K. Formation of three types of mixed dimers from four is isoenergetic. They are mediate between corresponding pure dimers of amines and carboxylic acids. This suggests further formation of mixed 2D-film with the domain structure.

Keywords

• aliphatic amines
• carboxylic acids
• enthalpy
• entropy
• gibbs’ energy of dimerization
• pm3 method