Synthesis of Some Methyl-10, 11-diaryl-undecanoates and 11-Aryl-9-undecenoates and Their Activity as Antioxidants and Corrosion Inhibitors

Abstract

Methyl 10-undecenoate and mercuric acetate were reacted in methanol to give methyl methoxyacetoxy mercury-undecanoate. The mercurial adduct was then reacted with phenol, o-cresol, m-cresol, p-cresol and o-tert-butylphenol in 1: 5 mole ratio each at 60 °C for one hour in the presence of perchloric acid as a catalyst, giving methyl 10, 11-diaryl undecanoates corresponding to the respective phenols. The reaction of the mercurial adduct and 2, 6-di-tert-butylphenol gave methyl 11- (hydroxy, di-tert-butylphenyl) 9-undecenoate instead of methyl 10, 11-diaryl undecanoate. The mercurial adduct was then reacted with methyl benzoate, dimethyl phthalate, and methyl acetylsalicylate at the same reaction condition for 2 hours, giving methyl 11-methoxycarbonylphenyl-9-undecenoate, methyl 11-dimethoxycarbonylphenyl-9-undecenoate, and methyl 11-acetoxymethoxycarbonylphenyl-9-undecenoate. All diaryl undecanoates listed above showed antioxidant activity for methyl oleate at 40 °C and 100 °C. However, their activities are somewhat less than the activity of BRA. They were found effective as corrosion inhibitors by the water-dip method with a sample of turbine oil and test pieces o mild steel, aluminium, zinc and brass at the concentrations of 0.2, 0.4, 0.6 and 0.8%. Especially, the derivatives from p-cresol and o-cresol were excellent as corrosion inhibitors. Methyl 11-methoxycarbonylphenyl-9-undecenoate, methyl 11-dimethoxycarbonylphenyl-9-undecenoate and methyl 11- (acetoxy, methoxycarbonylphenyl) -9-undecenoate were converted to its sodium, calcium, strontium and barium soaps, and their activity as corrosion inhibitors was tested with a sample of turbine oil and test pieces of mild steel at the concentrations of 0.2, 0.4, 0.6 and 0.8% by the water-dip method. Regerding the acid components, the activity was ranked in the order of 11- (hydroxy, carboxyphenyl) -9-undecenoic acid>11-dicarboxyphenyl-9-undecenoic acid>11-carboxyphenyl-9-undecenoic acid. As for the base components, strontium and barium soaps were very effective followed by calcium soaps, sodium soaps being slightly less effective.