4-Methylanilinium 4-hydroxybenzenesulfonate

In the crystal of the title molecular salt, C7H10N+·C6H5O4S−, the benzenesulfonate units are linked through phenol–sulfonate O—H⋯O hydrogen bonds, forming chains along the c-axis direction. These chains are linked via N—H⋯O hydrogen bonds involving two of the three H atoms of the ammonium group of the 4-methylanilium cation, giving rise to two-dimensional networks parallel to the bc plane which are further connected through an additional N—H⋯O interaction in which the third ammonium H atom is involved, generating a three-dimensional network.

In the crystal of the title molecular salt, C 7 H 10 N + ÁC 6 H 5 O 4 S À , the benzenesulfonate units are linked through phenolsulfonate O-HÁ Á ÁO hydrogen bonds, forming chains along the c-axis direction. These chains are linked via N-HÁ Á ÁO hydrogen bonds involving two of the three H atoms of the ammonium group of the 4-methylanilium cation, giving rise to two-dimensional networks parallel to the bc plane which are further connected through an additional N-HÁ Á ÁO interaction in which the third ammonium H atom is involved, generating a three-dimensional network.

Comment
The stucture of the title compound, (I), is shown in Figure 1. Bond lengh and angles are within the standard values (Allen et al., 1987). In the crystal the phenolsulfonate units are joined together through O4-H4···O3 hydrogen bonds, forming chains along the c crystallographic axis. These chains are subsequently linked together through N-H···O interactions involving the 4-methylanilium units. First, giving rise to a two-dimensional network parallel to bc plane, through interactions involving two of the three hydrogens of the ammonium moiety: N1-H1A···O2 and N1-H1C···O1 and finally generating a three-dimensional network through the use of the third hydrogen atom bonded to the nitrogen: N1-H1B···O4 (Table 1 and Figure 2).

Experimental
The 4-MAPS compound was synthesized by the reaction of equimolar mixture of 4-methyl aniline and phenolsulfonic acid. To a saturated solution of 4-methyl aniline in acetone, phenolsulfonic acid was slowly added at room temperature.
The solution was stirred for six hours to get an homogeneous solution, filtered and kept for slow evaporation at room temperature. After that a saturated solution of 4-MAPS was prepared by using methanol at room temperature. The prepared solution was kept to constant temperature in water bath at 30° C to avoid the effect of fluctuation in room temperature. An slow evaporation process was allowed for a period of 15 days. The grown crystals of an approximate size of 12 x 9 x 2 mm3 were harvested and re-crystallized to grow pure crystals for further studies.

Refinement
H atoms were positioned geometrically and treated as riding on their parent atoms, with C-H distance of 0.93 -0.96 Å, N-H distance of 0.89 Å, O-H distance of 0.82 Å and U iso (H) = 1.2Ueq(N and C aromatic ) and U iso (H) = 1.5Ueq( C methyl )