2-Ethyl-6-methylanilinium 4-methylbenzenesulfonate

The title compound, C9H14N+·C7H7SO3 −, contains a 2-ethyl-6-methylanilinium cation and a 4-methylbenzenesulfonic anion. The cations are anchored between the anions through N—H⋯O hydrogen bonds. Electrostatic and van der Waals interactions, as well as hydrogen bonds, maintain the structural cohesion.


Comment
In the title compound, the proton of the sulfonic group of sulfonic acid has been transferred to the N atom of the 2-ethyl-6methylaniline molecule, leading to the formation of the molecular complex, (I). In this article we present the crystal structure of the title compound. The removal of the sulfonic acid H atom leads to a shortening of the C10-S1 bond length, showing a partial double-bond character. This behaviour is similar to that observed in many picrate salts (Muthamizhchelvan et al. 2005); it is attributed to the loss of the hydroxyl proton, leading to the conversion of the neutral to an anionic state of the molecule.
In the structure (Fig. 1), intermolecular hydrogen bonds are observed, with the N atom of the cation acting as donors.
The orientation of the anion and cation facilitates the formation of the expected strong N-H···O hydrogen bonds between amino atom N1 and the sulfonic O atoms; N1 hydrogen bonds to two sulfonic O atoms of adjacent molecules (

Experimental
Added 2-ethyl-6-methylaniline (1.35 g) into a solution of 4-methylbenzenesulfonic acid (1.72 g) and ethanol (10 ml). After 10 min precipitate were formed which were filtered and dried, giving the desired product. Crystals suitable for X-ray structure determination were obtained by slow evaporation of an ethanol solution at room temperature.

Refinement
The methyl H atom were positioned geometrically (C-H = 0.98 Å) and torsion angles refined to fit the electron density [U iso (H) = 1.5U eq (C)]. Other H atoms were placed at calculated positions (methylene C-H = 0.95 Å and aromatic C-H = 0.95 Å) and included in the refinement in a riding mode with [U iso (H) = 1.2U eq (C)].   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.