3,4-Dimethylanilinium 4-methylbenzenesulfonate

In the crystal structure of the title compound, C8H12N+·C7H7O3S−, N—H⋯O hydrogen bonds link the cations and anions into ribbons parallel to the c axis. N—H⋯S interactions also occur.

In the crystal structure of the title compound, C 8 H 12 N + Á-C 7 H 7 O 3 S À , N-HÁ Á ÁO hydrogen bonds link the cations and anions into ribbons parallel to the c axis. N-HÁ Á ÁS interactions also occur.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: JH2327).

Comment
The title compound, was prepared as part of our ongoing studies of hydrogen-bonding interactions in the crystal structure of protonated amines. The importance of molecular salts as solid forms in pharmaceutical formulations is well known.For a given active ingredient, the isolation and selection of a salt with the appropriate physicochemical properties involves significant screening activity and has been discussed at some length in the literature (Tong & Whitesell et al. 1998;Shanker et al. 1994). Structures containing the dimethylanilinium cation have been already reported with tin chloride (Bouacida et al. 2008), sulfate (Singh et al. 2002), and dihydrogenphosphate. Here we report the synthesis and crystal structure of the title compound, 3,4-dimethylanilinium 4-methylbenzenesulfonate (Fig. 1).
The bond distances and bond angles in the title compound agree very well with the corresponding distances and angles reported for a closely related compound (Hemissi et al. 2001). In this structure, only one type of classical hydrogen bonds are observed, viz. cation-anion (Table 1). All three ammonium H atoms are involved in hydrogen bonds. These interactions result in the formation of cation-anion ribbons along c direction. Dipole-dipole and van der Waals interactions are effective in the molecular packing.

Experimental
To a stirred solution of 3,4-dimethylbenzenamine (2.42 g, 0.02 mol) in 30 mL of methanol, 4-Toluene sulfonic acid (3.8 g, 0.02 mol) was added at the room temperature. The precipitate was filtered and washed with a small amount of ethanol 95%. Single crystals suitable for X-ray diffraction analysis were obtained from slow evaporation of a solution of the title compound in water at room temperature.

Refinement
The H-atoms bonded to the C-atom were positioned geometrically and refined using a riding model, with C-H = 0.93-0.96 Å and U iso (H) = 1.2U eq (C). The H-atoms bonded to the N-atom were located from a difference map and were allowed to refine freely.  Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.