Formation of Unsaturated C₃ Hydrocarbons by the Protolysis of Magnesium Sesquicarbide with Ammonium Halides

The protolysis of magnesium sesquicarbide, Mg₂C₃, with inorganic acids provides an interesting alternative to the more common hydrolysis of ionic carbides for obtaining their respective hydrocarbons. In particular, protolysis reactions with ammonium halides as precursors for hydrogen halides were investigated using in situ methods such as TGA/sDTA/MS and high-temperature XRPD. The protolysis reactions with NH₄F and NH₄Cl revealed two different reaction mechanisms yielding C₃H₄ and the respective magnesium halides as expected products. In the case of NH₄Cl, intermediate phases that have not been previously observed, specificly (NH₄)₂MgCl₄ (I4/mmm) and two modifications of NH₄MgCl₃ (P6₃/mmc), were structurally characterized.