Crystal structure of allyl-ammonium hydrogen succinate at 100 K

The asymmetric unit of the title compound, C2H8N(+)·C4H5O4 (-), consists of two allyl-ammonium cations and two hydrogen succinate anions (Z' = 2). One of the cations has a near-perfect syn-periplanar (cis) conformation with an N-C-C-C torsion angle of 0.4 (3)°, while the other is characterized by a gauche conformation and a torsion angle of 102.5 (3)°. Regarding the anions, three out of four carboxilic groups are twisted with respect to the central C-CH2-CH2-C group [dihedral angles = 24.4 (2), 31.2 (2) and 40.4 (2)°], the remaining one being instead almost coplanar, with a dihedral angle of 4.0 (2)°. In the crystal, there are two very short, near linear O-H⋯O hydrogen bonds between anions, with the H atoms shifted notably from the donor O towards the O⋯O midpoint. These O-H⋯O hydrogen bonds form helical chains along the [011] which are further linked to each other through N-H⋯O hydrogen bonds (involving all the available NH groups), forming layers lying parallel to (100).