2,4-Dimethylanilinium perchlorate

The crystal packing of the title compound, C8H12N+·ClO4 −, is stabilized by N—H⋯O hydrogen bonds, the protonated amine group acting as a hydrogen-bond donor with the perchlorate O atoms as acceptors. These connect neighbouring cations and anions, forming a two-dimensional network. Variable-temperature dielectric constant measurements on the salt indicated that no distinct phase transition occurred within the measured temperature range of 80–293 K.

The crystal packing of the title compound, C 8 H 12 N + ÁClO 4 À , is stabilized by N-HÁ Á ÁO hydrogen bonds, the protonated amine group acting as a hydrogen-bond donor with the perchlorate O atoms as acceptors. These connect neighbouring cations and anions, forming a two-dimensional network. Variable-temperature dielectric constant measurements on the salt indicated that no distinct phase transition occurred within the measured temperature range of 80-293 K.
Data collection: CrystalClear (Rigaku, 2005); cell refinement: CrystalClear data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: PRPKAPPA (Ferguson, 1999 (2007) researched the crystal structure of the 2,4,6-trimethylanilinium iodide. This paper reports the crystal structure and dielectric properties of the related salt 2,4-dimethylanilinium perchlorate. The asymmetric unit of title compound, C 8 H 12 N + .ClO 4 -, contains a 2,4-dimethylanilinium cation and one perchlorate anion (Fig.1). The ammonium cations stack head-to-tail with no π-π interactions. The crystal packing is stabilized by N-H···O hydrogen bonds, the protonated amine group acting as a hydrogen-bond donor with the perchlorate O atoms as acceptors. These connect neighbouring cations and anions to form a two-dimensional network (Fig.2). In addition, the dielectric constant of title compound as a function of temperature indicates that the permittivity is basically temperature-independent (dielectric constant equaling to 2.6 to 4.5) from 80k to 293k, suggesting that no distinct phase transition occurred within the measured temperature range.
Experimental 2,4-dimethylbenzenamine (1.21 g, 10 mmol) and perchloric acid (1 g, 10 mmol) were mixed and the 2,4-dimethylbenzenamine perchlorate was obtained, then it was dissolved in water (3 ml), ethanol (20 ml), and the solution was filtered. After slowly evaporating over a period of 3 d, colorless prism crystals of the title compound suitable for diffraction were isolated.
CAUTION: Although no problems were encountered in this work, perchlorate compounds are potentially explosive. They should be prepared in small amounts and handled with care.

Refinement
Positional parameters of all the H atoms were calculated geometrically and were allowed to ride on the C, N atoms to which they are bonded, with C-H = 0.93 to 0.97 Å, U iso (H) = 1.2 Ueq(C), N-H = 0.89 Å, U iso (H)= 1.5 U eq (N). Fig. 1. The asymmetric unit of the title compound, with the displacement ellipsoids were drawn at the 30% probability level. A hydrogen bond is shown as a dashed line.

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.
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.