Ammonium [(1S)-(endo,anti)]-(-)-3-bromo-camphor-8-sulfonate.

In the title mol-ecular salt, NH(4) (+)·C(10)H(14)BrO(4)S(-), the norbornane skeleton of the anion is composed of two five-membered rings in envelope conformations and a six-membered ring with one Br atom, one carbonyl O atom and a methyl group held in a boat conformation by a bridging methyl-ene group. Short intra-molecular C-H⋯O and C-H⋯Br inter-actions occur. In the crystal, the component ions are linked by inter-molecular N-H⋯O and C-H⋯O hydrogen bonds.

In the title molecular salt, NH 4 + ÁC 10 H 14 BrO 4 S À , the norbornane skeleton of the anion is composed of two five-membered rings in envelope conformations and a six-membered ring with one Br atom, one carbonyl O atom and a methyl group held in a boat conformation by a bridging methylene group. Short intramolecular C-HÁ Á ÁO and C-HÁ Á ÁBr interactions occur. In the crystal, the component ions are linked by intermolecular N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds.
In the crystal, adjacent molecules of (I) are linked by intermolecular N-H···O and C-H···O hydrogen bonds (Table   1, Fig. 2).
3-Bromocamphor-8-sulfonic acid (1 g) was dissolved in 15 ml of ethanol and then 6 ml of NH 3 solution were added. The mixture was stirred until a clear solution was observed (about 20 min). The solution was slowly concentrated on water bath to half the volume over a 2 h period. The concentrate was allowed to crystallize undisturbed for 48 h. The resulting colourless prisms of (I) were carefully separated by filteration and washed with three 0.5-ml portions of petroleum ether.

Refinement
In the ammonium ion, H atoms bound to N atoms were located in difference Fourier maps and their positional parameters were refined freely using a DFIX instruction [N-H = 0.93 (3) Å] in SHELXL97, with U iso (H) = 1.5U eq (N). H atoms bound to C atoms were placed in idealized positions and refined using a riding model with C-H = 0.96, 0.97 and 0.98 Å for CH 3 , CH 2 and CH, respectively. U iso (H) values were set at 1.5U eq (C) for the methyl groups, and 1.2U eq U eq (C) for other H atoms. Fig. 1. View of (I) with displacement ellipsoids drawn at the 30% probability level.

Special details
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and tor-

sion angles
Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted Rfactors wR and all goodnesses 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 observed criterion of F 2 > σ(F 2 ) is used only for calculating -R-factor-obs 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.