Crystal structure of N,N,N-triethylhydroxylammonium chloride

The cation and anion in N,N,N-triethylhydroxylammonium chloride are linked by an O—H⋯Cl hydrogen bond. The extended structure displays C—H⋯Cl and C—H⋯O hydrogen bonds, resulting in layers lying parallel to the (100) plane: further C—H⋯Cl contacts connect the sheets into a three-dimensional network.


Chemical context
Triethylamine is often used to treat silica gel with the goal of reducing the acidity of the stationary phase during column chromatography purification. In a typical procedure, an eluant is mixed with triethylamine (1-3%), and this solvent mixture is used to prepare the silica gel slurry for manually packed columns. While the effect of the triethylamine on silica gel is known, no specific details could be found about the structural transformation of triethylamine itself. This work presents the result of the column chromatography purification of a dithiazolo[4,5-a:5 0 ,4 0 -c]phenazine derivative using a dichloromethane:ethyl acetate mixture as eluant. Unexpectedly, the crystals obtained after slow solvent evaporation from an 'empty' fraction were identified as the title molecular salt, N,N,N-triethylhydroxylammonium chloride, 1.

Structural commentary
The molecular structure of 1 is presented in Fig. 1 (Jiang et al., 2004;Ré rat, 1960;Caron & Donohue, 1962). The hydroxyl hydrogen atom H1 participates in a strong hydrogen bond with the adjacent chloride anion (Table 1), which is also observed for 2.
For comparison, the crystal packing of 2 is rather different. The cations in 2 lie on mirror planes and are arranged into chains along the [100] direction, being linked by O1-H1Á Á ÁCl1 and C2-H5Á Á ÁCl1 hydrogen bonds. The molecules in the chain are symmetrically related by a glide plane and C1-H2Á Á ÁCl1 hydrogen bonds connect the chains into three-dimensional network. It is noteworthy that the oxygen atom does not participate as a proton acceptor in hydrogen bonding. Layers in the crystal structures of (left) 1 and (right) 2.

D-HÁ
the anion is Cl À , of which seven feature an O-HÁ Á ÁCl hydrogen bond (the OÁ Á ÁCl distance varies from 2.872 to 3.010 Å ). The exception is the crystal structure of (1S,5S)geneseroline hydrochloride monohydrate (refcode VAVZUN), in which the solvent water molecule accepts an O-HÁ Á ÁO hydrogen bond from the C 3 N + -OH group.

Synthesis and crystallization
During the column chromatography purification of the dithiazolo[4,5-a:5 0 ,4 0 -c]phenazine derivative using dichloromethane-ethyl acetate as eluant and Alfa-Aesar silica gel (stock # 42570; lot # K03T015; case # 632131-67-4) treated with triethylamine, a fraction containing a trace amount of the desired product was left over several days until compete evaporation of the solvents led to the formation of colourless plates of the title compound. Unexpectedly, the crystals were identified as N,N,N-triethylhydroxylammonium chloride; dichloromethane was probably the source of the chloride anion.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. H atoms were all located in difference Fourier map and refined isotropically.  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.