2-Aminoanilinium 4-methylbenzenesulfonate

In the extended structure of the title molecular salt, the cations and anions are linked by N—H⋯O hydrogen bonds to generate [010] chains.

In this report, we describe the crystal structure of the title salt, 1, which is the third anhydrous compound that can be isolated from the benzene-1,2-diamine/4-methylbenzene-1-sulfonic acid/water system. The title salt was obtained by an aqueous reaction of the aromatic diamine with 4-methylbenzene-1-sulfonic acid in a 2:1 molar ratio, unlike 2, which was crystallized from a 1:2 reaction.
The asymmetric unit of 1 consists of one 2-aminoanilinium cation and one 4-methylbenzene-1-sulfonate anion ( Fig. 1) with all atoms located in general positions. The geometric parameters of the cation and the anion are in their normal ranges and are in agreement with previously reported data (Mishra & Pallepogu, 2018;Narvekar & Srinivasan, 2020).
All the oxygen atoms attached to the sulfur atom of the sulfonate moiety of the anion function as hydrogen-bond acceptors (Fig. 2), while four of the five H atoms attached to the N atoms of the 2-aminoanilinium cation function as hydrogen-bond donors, resulting data reports in a total of four N-HÁ Á ÁO hydrogen bonds (with two occurring within the arbitrarily chosen asymmetric unit; Table 1). Thus, the cations and the anions are linked only via N-HÁ Á ÁO hydrogen bonds, as observed earlier for 2. The extended structure of 1 features [010] hydrogen-bonded chains, with adjacent cations and anions related by the 2 1 screw axis (Fig. 3).

Figure 3
A view down [010] of the packing in 1 with N-HÁ Á ÁO hydrogen bonds shown as dashed lines.

Figure 1
The molecular structure of 1 with displacement ellipsoids drawn at 50% probability level. Hydrogen bonds are shown as blue dashed lines.

Figure 2
The hydrogen-bonding scheme around the 4-methylbenzene-1-sulfonate anion. Symmetry codes: (i) -x + 1, Ày, Àz + 1; (ii) Àx + 1, Ày + 1, Àz + 1.  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.