2-Hydroxyethanaminium 2-methyl-5-nitrobenzenesulfonate

In the crystal structure of the title salt, C2H8NO+·C7H6NO5S−, the cations and anions are linked together by N—H⋯O and O—H⋯O hydrogen bonds, forming layers parallel to (100). The plane of nitro group is skew with respect to the plane of benzene ring, making a dihedral angle of 17.5 (2)°.

In the crystal structure of the title salt, C 2 H 8 NO + ÁC 7 H 6 NO 5 S À , the cations and anions are linked together by N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds, forming layers parallel to (100). The plane of nitro group is skew with respect to the plane of benzene ring, making a dihedral angle of 17.5 (2) .
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: IS5129).
A few crystal structures containing 2-methyl-5-nitrobenzenesulfonate have been reported previously, they are pyridinium derivative (Gu et al., 2007), nickel (Xie, Yang et al., 2006), magnesium (Xie et al., 2007), and potassium salts (Xie, Lui & Yuan, 2006). In the potassium salt, all of the oxygen atoms of sulfonate and one oxygen atom of the nitro group is coordinated with potassium atom directly. However, there exists no covalent bond between the counter ion pair in the title compound, which is similar with the other three previous cases. In all of these cases, one of C-C bond of benzene rings are slightly abormal.
In the crystal, the 2-hydroxyethanaminium cations and the MNB anions are linked by N-H···O and O-H···O hydrogen bonds (Table 1) to form thick layers ( Fig. 2) parallel to the (100) plane. The nearest separation between the centroid of MNB benzene rings is of 4.483 (3) Å, suggesting no π-π interaction. This situation is similar to that observed in the case containing a large sized organic cation as counter ion for MNB anion (Gu et al., 2007), but is different from those observed in other cases containing metal cations as counter ion for MNB anion (Xie et al., 2007;Xie, Lui & Yuan, 2006;Xie, Yang et al., 2006).

Experimental
2-Methyl-5-nitrobenzenesulfonic acid (12.1 g) and 2-ethanolamine (5.0 g) were mixed and dissolved in sufficient water (25 ml) by heating to 373 K, at which point a clear solution resulted. The solution was then cooled slowly to room temperature. Crystals of the title compound (9.2 g) were formed upon the evaporation of water, then collected and washed with ethanol.

Refinement
All H atoms of hydroxyl and ammonium groups were located in a difference Fourier map. The H atoms of ammonium group were refined freely, but the H atom of hydroxyl group was refined with a distance restraint O-H = 0.82 (1) Å, and with U iso (H) = 1.5U eq (O). Other H atoms were placed in calculated positions (C-H = 0.93-0.97 Å) and allowed to ride on their parent atoms, with U iso (H) = 1.2U eq (C).

Figure 1
The asymmetric unit of the title compound with labeling and displacement ellipsoids drawn at the 40% probability level.
One N-H···O hydrogen bond is illustrated as a dashed line.  The hydrogen bonding layer of the title compound viewed down along the b axis. Hydrogen bonds are drawn as dashed lines. The H atoms not involved in the hydrogen bonds have been omitted for clarity. Hydrogen site location: inferred from neighbouring sites H atoms treated by a mixture of independent and constrained refinement w = 1/[σ 2 (F o 2 ) + (0.0532P) 2 + 0.342P] where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.28 e Å −3 Δρ min = −0.39 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.095 (5) Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 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.