Kinetics of the aminolysis of hydrogenated tallow by allylamine and other primary amines in methanol

Kinetics of the aminolysis of hydrogenated tallow by allylamine in methanol solution under sodium methoxide catalysis was studied at several temperatures (60 to 90C) and catalyst concentrations. Under the experimental conditions the triglycerides were rapidly converted to the mixed methyl esters, which slowly reacted with the amine to produce the mixed amides. At constant catalyst concentration, disappearance of triglyceride was found to be first order in triglyceride and in amine. Because rate was found to be directly proportional to catalyst concentration, the experimental over‐all rate was 蜢d[Triglyceride]/dt=k3[Triglyceride] [Amine] [RO蜢], and k3 was 2.022 kg2 mole蜢2 hr蜢1. A mechanism proposed by Bunnett and Davis for ester aminolysis involving an ester‐amine complex formed in a rapid pre‐transition‐state equilibrium is consistent with thermodynamic terms which reconcile a large negative entropy of activation (蜢44.17 cal deg蜢1 equivalent蜢1) and relatively small energy of activation (11.60 kcal equivalent蜢1). Relative rate constants at 70C under sodium‐methoxide catalysis for the aminolysis of hydrogenated tallow by a variety of structurally different primary amines agreed, in general, with those found by others for the ethylene glycol‐catalyzed reaction of methyl acetate with the same amines at 25C. However, monoethanolamine reacted nineteen times faster than predicted, which suggested a mechanism involving initial attack by the alkoxy anion of the ethanolamine in the rate detering step, followed by rapid, base‐catalyzed, acyl acyl oxygen‐to‐nitrogen (O薔N) migration. The velocity constants and thermodynamic constants reported enable prediction of the time required for specific yields under a variety of experimental conditions.