Optimization of conditions for 2,2,6,6-tetramethyl-1-piperidinyl oxoammonium ion/sodium hypochlorite-catalyzed selective oxidation of the primary alcohol in 1-Monolaurin

Response surface methodology (RSM) was used to determine the optimum conditions for complete chemo-selective oxidization of the primary alcohol group in 1-monolaurin (1-ML) with dual catalysts, 2,2,6,6-tetramethyl-1-piperidine oxoammonium (TEMPO) and sodium hypochlorite (NaClO). Reaction conditions that required (i) the least amount of catalyst and (ii) the shortest reaction time were established. A statistical model of the degree of oxidation was proposed by response surface regression considering 5 factors: reactant pH, concentrations of the 2 catalysts, and reaction temperature, and time. Based on this proposed model, the relative effect of each factor could be predicted. The conditions that resulted in the lowest consumption of catalyst enabled oxidization of 2.744 g of 1-ML completely within 81 min with 18.4 mg TEMPO and 19.6 mL NaClO (pH 9.66, 34.5°C). The fastest reaction time (72 min) required 21.8 mg TEMPO and 19.9 mL NaClO (pH 10.98, 34.8°C). FT-IR and ¹³C NMR analysis revealed that 1-ML was completely oxidized under 2 different optimal conditions and the chemoselective oxidation of the primary alcohol occurred without oxidation of a secondary alcohol. After chemo-selective oxidation, 1-ML retained antibacterial activity against Gram-positive bacteria.