Estimated enthalpy of formation of N-[3-(Dimethylamino)propyl] hexadecanamide by experimental approach

Abstract

The N-[3-(Dimethylamino)propyl] hexadecanamide molecule is an important intermediate for synthesizing amphoteric and quaternary ammonium surfactants. Despite its importance for the household and personal care sectors, little to no information about its enthalpy of formation is found in the NIST database or literature, which hinders many industrial operations, especially its chemical production, by consuming much more energy than what is necessary. In this work, we present a first estimative of N-[3- (Dimethylamino)propyl] hexadecanamide's standard enthalpy of formation with a simple procedure that can be used to obtain similar parameters in chemical industry laboratories. The enthalpy estimative was obtained by reacting palmitic acid and dimethylaminopropylamine (DMAPA), yielding the desired compound. Hess's law was used to determine the enthalpy of the reaction through the heat associated with the extent of the reaction. The reagents were contacted in a simple calorimeter at room temperature (diluted with acetone) and 100 ºC (without acetone). The extent of the reaction was obtained by quantitative determination of the reaction medium in gas chromatography. The room temperature experiment led to an insignificant reaction extent which generated an unreliable result for the compound's enthalpy of formation. In contrast, at 100 ºC, the estimated standard enthalpy of the reaction was adequately calculated, leading to an enthalpy of formation of -703.93 ± 9.17 kJ/mol for the N- [3-(Dimethylamino)propyl] hexadecanamide. With this simple procedure, the industrial reactor's more precise heat consumption can be calculated, yielding economic and environmental benefits.