A second monoclinic polymorph of 2,4-dimethylanilinium chloride

A second monoclinic polymorph of 2,4-dimethylanilinium chloride, C8H12N+·Cl−, (I), is reported. The unit-cell dimensions differ from those of the first reported monoclinic form, (II) [Yao (2010 ▶). Acta Cryst. E66, o1563]. Nevertheless, both compounds crystallize in the monoclinic space group P21/n. As in (II), the protonated amine group in (I) acts as a hydrogen-bond donor to the chloride ion, forming three N—H⋯Cl hydrogen bonds. The result is a two-dimensional network in the ac plane. The difference in the hydrogen-bond pattern is that in (I) only 12-membered rings are formed whereas in (II), eight-membered and 16-membered rings are formed.


Related literature
For another monoclinic polymorph of the title compound, see: Yao (2010). For properties of compounds containing inorganic anions and organic cations, see: Masse et al. (1993); Xiao et al.  Table 1 Hydrogen-bond geometry (Å , ).

Comment
The combination of organic cations and inorganic anions is important in material science and chemistry because of their abilities to join the properties of organic and inorganic molecules, exhibiting some interesting crystal structures with special properties, such as luminescence, magnetism, and multifunctional properties (Masse et al., 1993). Furthermore these hybrid materials have a great interest due to their numerous varieties of intriguing structural topologies (Xiao et al., 2005).
The title compound, (I), is a second monoclinic polymorph of the structure of 2,4-dimethylanilinium chloride which crystallizes in the space group P2 1 /n. A different structure, (II), in the space group P2 1 /c was described earlier by (Yao, 2010).
The asymmetric unit of the title compound contains one 2,4-dimethylanilinium cation and one chloride anion (Fig. 1).
The two-dimensional arrangement of the chloride anions and 2,4-dimethylanilinum cations in the unit cell is shown in

Experimental
An ethanolic solution of 2,4-dimethylaniline (1.21 g, 10 mmol in 10 ml) was added dropwise to a magnetically stirred of aqueous hydrochloric acid solution (1.01 g, 10 mmol) a 1:1 molar ratio. The achieved solution is then filtered to eliminate the colorless crystals precipitated formed and then stirred for 2 hrs. After stirring, the obtained solution was slowly evaporated at room temperature over several days resulting in the formation of 2,4-dimethylanilinium chloride crystals.

Refinement
The hydrogen atoms of the protonated nitrogen were found in difference Fourier map and refined isotropically.   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.