Oxidation of acetate ions by nitrate and nitrite melts

Abstract

The stoichiometry of the oxidation of acetate ion by molten sodium nitrate-potassium nitrate is more complicated than two earlier investigations indicated. Ammonia, found for the first time, is a major product along with the previously reported products, nitrite and carbonate, the ratios with respect to initial acetate being 0·3–0·5, 0·25–0·45 and 1·0–1·5, respectively. The nitroacetate ion, as the mono- or dianion, is suggested as an intermediate, the formation of a carbon-nitrogen bond also being suggested by the evolution of hydrogen cyanide from the solidified partially reacted melt. Addition of potassium hydroxide increases the rate of reaction but decreases the yield of ammonia, similar increases in rate being found for the oxidation of potassium benzoate and potassium phthallate in conformity with a carbanion mechanism. The reaction rate of sodium acetate in molten sodium nitrite is also increased by potassium hydroxide, but with an increase in the yield of ammonia, while cyanide ions are now found to be a significant intermediate product. In the presence of a Lux-Flood acid, sodium dimolybdate, acetate oxidises to produce water, ammonia and acetic acid, together with a trace of acetone. All the evidence is in accord with the first steps of the nitrate melt oxidation being the hitherto unreported nitrative decarboxylation reaction.