METHYLAMINE AND DIMETHYLAMINE SALTS OF THE HYDROGEN MALEATE ION

Methylammonium hydrogen maleate, CH6N+.C4H3O4-, crystallizes in space group Pnam with two independent anions in the asymmetric unit having c rystallo-graphic mirror planes bisecting the C=C bonds. Dimethylammoni um hydrogen maleate, C2H8N+.C4H3O4-, crystallizes in space group P2(1) /n without crystallographic symmetry constraints on the hydrogen malea te ion and this anion also possesses almost perfect mirror-plane symme try. One of the anions in the methyl ammonium salt displays significan t deviation from planarity [-12.00(9)degrees]. The symmetry of the thr ee anions and the difference in their conformations are rationalized f rom the hydrogen-bond interactions in the two salts.