A new polymorph of ammonium succinate - serendipity in action.

Succinic acid has been known since 1546 and was first chemically identified in the mid-19th century. In an attempt to prepare a molecular salt of succinic acid with (S)-(-)-α-methylbenzylamine, we have obtained the second polymorph of the monoammonium salt of succinic acid, NH4+·C4H5O4-. The crystal structure determination proves the structure of the ionic compound and the intimate role of the ammonium ion in the structure, which is compared to the earlier described polymorph.