Infrared study of the surface reaction of gaseous sulphuryl chloride with metal carboxylates

Abstract

The surface reaction of metal carboxylates RCO₂M (R = H, Me, Et, Prⁿ, and Prⁱ; M = Li, Na, and K) with gaseous sulphuryl chloride has been monitored by i.r. spectroscopy. Reactions (I) and (II) take place. 2RCO₂M + SO₂Cl₂→ RCOMSO₄+ RCOCl + MCl (I), 2RCO₂M + SO₂Cl₂→ 2RCOCl + M₂SO₄(II). Process (I) is observed for all carboxylates except the formates and the lithium salts at 18–30°C. Sodium acetyl sulphate is formed at room temperature by process (I). After removal of CH₃COCl formed in process (I) and SO₂Cl₂, when the mixture is heated to 150°C, it reacts further with the carboxylate to give the anhydride and sodium sulphate. In case of potassium acetyl sulphate, when the mixture is heated to 150°C after the removal of CH₃COCl and SO₂Cl₂, it gives some ester and K₂CO·O·SO₃ in addition to the anhydride. Process (II) occurs for the formates and the lithium salts at room temperature. In the case of the reaction of the formates at room temperature, formyl chloride as the product reacts immediately with sodium and potassium formate to give formic anhydride and with lithium formate to yield formic acid. At 150°C, all the carboxylates mainly react with sulphuryl chloride according to process (II), and the acyl chloride as product reacts with the carboxylates except the formates to form the anhydride, and the formate to give formic acid. However, in the reaction of potassium acetate at 150 °C, some of the acetyl sulphate as product decomposes with the acetate to give K₂CO·O·SO₃, methyl acetate, and carbon monoxide. This suggests that the process (I) takes place to some extent at 150°C.