Isothermal and isochoric crystallization of highly hygroscopic pyridineN-oxide of aqueous solution

Abstract

Highly hygroscopic pyridine N-oxide, C5H5NO, dissolves in water absorbed from atmospheric air, but it crystallizes in the neat form of the aqueous solution under high pressure. The crystals grown at high-pressure isochoric conditions are of the same phase as that obtained from anhydrous crystallization at ambient pressure. This feature can be employed for retrieving compounds highly soluble in water from their aqueous solutions. The crystal structure is strongly stabilized by CH...O contacts. The crystal compression and thermal expansion as well as three shortest H...O distances comply with the inverse-relationship rule of pressure and temperature changes.

The molecular structure of 4-methylpyridine-N-oxide: Gas-phase electron diffraction and quantum chemical calculations

“…The parameters obtained in our research is in a good agreement with the theoretical results (therein and [18]) and, also, with the parameters for non-substituted N-oxide in contrast to the values recommended by Chiang J. F. et al [15]. Furthermore, the parameters of free molecules of PyO [14] and 4-Me-PyO obtained in this work are in a good agreement with the crystal structures [34,35]. Apparently, some increase of the semipolar N/O bond lengths in the crystal phase compared to free molecules is due to intermolecular hydrogen bonding.…”

Molecular structure and electron distribution of 4-nitropyridine N-oxide: Experimental and theoretical study of substituent effects

“…Table 4 compares the structure of pyridine-N-oxide and its two substituted obtained by GED, X-ray and DFT. Taking into account that the structural parameters obtained by different methods have different physical meaning, we can note a good agreement of the values obtained in our research (therein and [24]) with the theoretical results (therein and [21]) and, also, with the parameters for the crystals [46,47] in contrast to the values recommended by Chiang J. F. et al [20]. Apparently, some increase of the semipolar N/O bond lengths in a crystal phase compared to the free molecules is due to intermolecular hydrogen bonding.…”

Crystal structure of 3,5-dimethylpyridineN-oxide dihydrate

“…powder (70%). The same strong hygroscopic character was previously noted for pyridine N-oxide (Ü lkü et al, 1971;Patyk et al, 2014). The powder was dissolved in diethyl ether and left to slowly evaporate at 277 K, to give clear colourless crystals (m.p.…”