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Preparation of alkyl 11-anilino-10-hydroxy undecanoates and evaluation of their antioxidant activity


Correspondence: Dr. Rachapudi Badari N. Prasad, Centre for Lipid Research, Indian Institute of Chemical Technology, Hyderabad, Andhra Pradesh 500 007, India


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A novel class of 10-undecenoic acid-based alkyl 11-anilino-10-hydroxy undecanoates were prepared by reacting n-alkyl (C1 and C4) and iso alkyl (C3, C4, and C8) epoxy undecanoates with aniline under catalyst-free reaction conditions. The synthesized products were characterized by 1H NMR, IR, GC, and GC-MS and evaluated for their antioxidant activity using rancimat and differential scanning calorimetry (DSC) methods. The effect of antioxidants was studied at 0.25 and 0. 5% concentrations using rancimat method and at 0.5% in DSC analysis by adding in a lubricant base stock, namely epoxy karanja fatty acid 2-ethylhexyl esters. All the products exhibited good antioxidant properties at 0.25% concentration and enhanced antioxidant activity with the increased antioxidant concentration at 0.5%. The results obtained from isothermal DSC correlated well with those based on the rancimat method. n-Butyl 11-anilino-10-hydroxy undecanoate (4c) exhibited the best stabilizing effect on lubricant base stock with longest induction time compared to butylated hydroxytoluene (BHT) and other products. The data indicate that the synthesized products are potential antioxidants for lubricant formulations.