4-Acetylpyridinium hydrogen sulfate

The crystal structure of the title compound, C7H8NO+·HSO4 −, consists of O—H⋯Ohydrogen-bonded extended chains of hydrogen sulfate anions. Each hydrogen sulfate anion is furthermore connected to one 4-acetylpyridinium cation via a hydrogen bond of the N—H⋯O type.

The crystal structure of the title compound, C 7 H 8 NO + ÁHSO 4 À , consists of O-HÁ Á ÁOhydrogen-bonded extended chains of hydrogen sulfate anions. Each hydrogen sulfate anion is furthermore connected to one 4-acetylpyridinium cation via a hydrogen bond of the N-HÁ Á ÁO type.
The asymmetric unit of the title compound contains one 4-acetylpyridinium cation and one hydrogen sulfate anion (Fig 1).
In the anion, the bond length of S1-O3 is 1.553 (6) Å compared to the average bond length of 1.438 (5) Å of the other S1-O bonds. It is therefore reasonable that the hydrogen atom of hydrogen sulfate is bonded to O3. The supramolecular structure consists of infinite chains of anions with one cation linked to each anion via an additional hydrogen bond (N1-H1B···O1 2.774 (8) Å, Fig 2).
Experimental 4-Acetylpyridine was obtained according to the method described by Piner (1934). Reaction of equimolar amounts of 4acetylpyridine and H 2 SO 4 produced a precipitate. This was filtered off, dried and dissolved in 96% ethanol from which single crystals were grown by slow evaporation of the solvent at room temperature.

Refinement
The H atom connected to O3 was discernible from difference electron-density map. Nevertheless, it was placed to the ideal position, with S1-O3-H angle tetrahedral, allowing the H atom to ride on the immediately preceding atom O3 and rotate about the S1-O3 bond, refined in a riding atom approximation with a constrained bond length of O-H = 0.82 Å. Positional parameters of the other H atoms were calculated geometrically with C ar -H = 0.93 Å and C Me -H = 0.96 Å and were allowed to ride on the corresponding C atoms with U iso (H) = 1.2 U eq (C). In the absence of significant anomalous dispersion effects, 860 Friedel pairs were merged. Fig. 1. Molecular structure of the title compound with the atomic numbering scheme. Displacement ellipsoids are drawn at the 30% probability level and all H atoms have been omitted for clarity.  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.