Selective amidation of fatty methyl esters with N‐(2‐aminoethyl)‐ethanolamine under base catalysis

The reaction of N‐(2‐aminoethyl)‐ethanolamine (AEEA) with saturated fatty methyl esters derived from coconut oil occurs under noncatalyzed conditions to yield principally N‐(2‐hydroxyethylamino)‐ethyl fatty amide,1, derived from the condensation of the primary amine moiety of AEEA with the methyl ester. In the presence of 0.25 wt % sodium methoxide at low reaction temperatures (<90 C), 2 carboxamides are formed, the secondary monoamide,1 and also the tertiary monoamide, N‐(2‐aminoethyl)‐N‐(2‐hydroxyethyl) fatty amide,2. As this mixture of secondary and tertiary monoamides is heated to higher reaction temperatures (>120 C), the concentration of secondary monoamide1 increases with a concomitant decrease in tertiary monoamide2. As the reaction time is increased at the elevated temperature, the tertiary monoamide continues to disappear. Increasing the base concentration to 2.5 wt % sodium methoxide, promotes selective formation of amide2 at low temperature. The results constitute evidence that at least 2 mechanisms are operating in fatty methyl ester amidations with AEEA and provide a classic example of thermodynamic vs kinetic control. Because amides1 and2 are intermediates to imidazoline amphoteric surfactants (powerful detergents, wetting agents, emulsifiers and so forth), knowledge of the reaction mechanisms in operation during the condensation of fatty methyl esters with AEEA will permit better understanding of the resultant products and the related processing conditions.