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The title salt, C 4 H 6 N 3 O 2 + ·Cl − , exhibits multiple hydrogen-bonding interactions involving the nitroimidazolium cation and the chloride anion. Strong hydrogen bonds between the amine hydrogen atom and the chloride anion link the ionic moieties. Of note, with respect to H...Cl interactions, the central aromatic hydrogen atom displays a shorter interaction than the other aromatic hydrogen atom. Finally, interactions are observed between the nitro moiety and methyl H atoms. While no π–π stacking is observed, anion-π interactions are present. The crystal was refined as a two-component twin. 

Numerous non-covalent interactions link together discrete molecules in the crystal structure of the title compound, 2C 20 H 26 N 2 O 2 2+ ·4Cl − ·H 2 O {systematic name: 4-[(5-ethenyl-1-azoniabicyclo[2.2.2]octan-2-yl)(hydroxy)methyl]-6-methoxyquinolin-1-ium dichloride hemihydrate}. A combination of hydrogen bonding between acidic H atoms and the anions in the asymmetric unit forms a portion of the observed hydrogen-bonded network. π–π interactions between the aromatic portions of the cation appear to play a role in the formation of the long-range ordering. One ethylene double bond was found to be disordered. The disorder extends to the neighboring carbon and hydrogen atoms. 

The stereocontrolled three-step synthesis of either enantiomer of α-thujone from commercially available 3-methyl-1-butyne is described. The enantioselectivity originates from a Brown crotylation which is then conferred to the all-carbon quaternary center via chirality transfer in a gold-catalyzed cycloisomerization. The route is highly atom economical and requires no protecting groups or redox manipulations. 

Abstract Two crystals incorporating the thiamine·HCl cation and the fluorinated anion 1,3-disulfonylhexafluoropropyleneimide have been characterized via single-crystal X-ray diffraction. The host-guest interactions of thiamine with the anions are analyzed and characterized using Hirshfeld surface analysis. The cations in both structures form a dimer in the solid-state via reciprocal hydrogen bonding through the amine and hydroxyl moieties. Additional investigation into the interactions responsible for dimer formation found that the sulfur atom in the thiazolium ring interacting with several hydrogen atoms to form stabilizing interactions. These interactions in the dimer are further analyzed using reduced density gradient analysis and the results are correlated to the fingerprint plots derived from the Hirshfeld surfaces. Moreover, specific interactions are observed from the cyclical anions, with both the fluorine and sulfonyl oxygen atoms participating in bridging interactions, displaying the diverse host-guest properties of thiamine. 

The crystal structure of the product of the neutralization reaction between 3-nitrobenzoic acid and pyridine is reported. The entities that crystallized are a pyridinium cation, a 3-nitrobenzoate anion and a 3-nitrobenzoic acid molecule in a 1:1:1 molar ratio, C 5 H 6 N + ·C 7 H 4 NO 4 − ·C 7 H 5 NO 4 . Distinct sets of hydrogen bonds link the pyridinium and benzoate ions (N—H...O) and the acid and benzoate moieties (O—H...O). The hydrogen bonding along with π–π stacking between the acid and benzoate moieties accounts for the long-range ordering of the crystal.