Crystal structures of 2-methylpyridinium hydrogen 2,3-bis(4-methylbenzoyloxy)succinate and bis-[4-methylpyridinium hydrogen 2,3-bis(4-methylbenzoyloxy)succinate] pentahydrate

The 1:1, 2-methylpyridium and 4-methylpyridinium salts of the chiral 4-methylbenzoyloxy-substituted succinic acid form, respectively one- and two-dimensional hydrogen-bonded crystal structures,


Structural commentary
In both the salts of 2,3-bis(4-methylbenzoyloxy)succinic acid [(I) and (II), Figs. 1 and 2, respectively], the N atoms of the pyridine molecules are protonated. With (I), the asymmetric unit comprises a single 2-methylpyridinium cation and a succinate mono-anion ( Fig. 1) whereas with (II), the asymmetric unit comprises two 4-methylpyridinium cations and two succinate mono-anions along with five water molecules of

Synthesis and crystallization
The title salts (I) and (II) were synthesized using the reaction of equi-molar quantities of di-p-tolyl-l-tartaric acid (0.967 g) and 0. The molecular structure of the two independent cation and anion pairs and the water molecules of solvation in the asymmetric unit of the title salt (II), with 30% probability displacement ellipsoids. Inter-species hydrogen bonds are shown as dashed lines. Table 2 Hydrogen-bond geometry (Å , ) for (II).

Figure 3
The crystal packing of the title salt (I) in the unit cell, viewed along the a axis. The hydrogen bonds are shown as dashed lines and H atoms not involved in hydrogen bonding have been omitted. and then kept at room temperature for slow evaporation. After 2 months, crystals of (I) or (II), suitable for X-ray diffraction analysis were obtained.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. C-bound H atoms were placed in calculated positions and allowed to ride on their carrier atoms, with C-H = 0.93 Å (aromatic CH), 0.98 Å for CH, or 0.96 Å (methyl CH), and with U iso = 1.5U eq (methyl C or O) and U iso = 1.2U eq (aromatic and methylene C The crystal packing of the title salt (II) in the unit cell, viewed along the b axis. The hydrogen bonds are shown as dashed lines. H atoms not involved in hydrogen bonding have been omitted.  (Parsons et al., 2013).   (Sheldrick, 2015) and PLATON (Spek, 2009).   (Parsons et al., 2013). Absolute structure parameter: 0.4 (4)

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.