(1-Hydroxyethylidene)(methyl)azanium bromide–N-methylacetamide (1/1)

The asymmetric unit of the organic hybrid salt, C3H8NO+·Br−·C3H7NO, comprises an N-methylacetamide cation, a N-methylacetamide molecule and a bromide anion. The amide species are linked head-to-head through a short O⋯H⋯O hydrogen bond, giving a monocation, which is extended by N—H⋯Br hydrogen bonds into chains along the b-axis direction.


Related literature
For general background to frameworks and structural phase transitions, see: Ye et al. (2009) ;Zhang et al. (2009). For the structure of the hemihydrochloride of N-methylacetamide, see: Jaber et al. (1983 Table 1 Hydrogen-bond geometry (Å , ).

Bin Wei Comment
Recent studies have revealed that small molecular compounds which have one or more amidogens may possess dielectric-ferroelectric properties (Ye et al., 2009;Zhang et al., 2009). Our research has been aimed at the synthesis of aromatic amidogen-containing compounds which may possess these properties. As part of our ongoing studies, we report here the crystal structure of the title compound, C 6 H 15 N 2 + Br -, the hydrobromide of N-methylacetamide The structure of the analogous hydrochloride of N-methylacetamide has previously been reported (Jaber et al., 1983).
The structure of the title compound, determined at ambient temperature (298 K), reveals that the asymmetric unit contains an N-methylacetamide cation, a N-methylacetamide molecule and a bromide anion (Fig. 1). The transferred proton is found within a short O1···H···O2 hydrogen bond (Table 1) linking the two molecules head-to-head in the monocation. These cations and the bromide anions form N-H···Br hydrogen-bonding associations giving onedimensional chains which extend along the b-cell direction (Fig. 2). Unfortunately, the dielectric constant of the title compound as a function of temperature indicates that the permittivity is basically temperature-independent below the melting point (368-369 K) and that it has no dielectric disuniform from 80 K to 405 K.

Experimental
The N-methylacetamide(1.46 g, 20 mmol) and hydrobromic acid (1.62 g, 20 mmol) was combined in 30 ml of aqueous solution. The mixture was stirred for 30 min to allow complete reaction and good quality blocky single crystals were obtained by slow evaporation after ca. two weeks (yield, 42%)

Refinement
The H atoms on the amide groups and the H within the short intramolecular O···H···O hydrogen bond were located in difference-Fourier analysis and their positional and isotropic displacement parameters were refined. The methyl H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms with C-H = 0.96 Å and with U iso (H) = 1.5U eq (C).
Displacement ellipsoids are drawn at the 30% probability level.  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 R-factors(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.