Temperature-dependent solid-state phase transition with twinning in the crystal structure of 4-methoxyanilinium chloride

We report the high temperature structure at 250   K and the low-temperature structure at 100   K. In the low-temperature structure, the – NH3 hydrogen atoms are ordered and this group has a different orientation in each independent molecule, in keeping with optimizing N — H...Cl hydrogen bonding, some of which are bifurcated: these hydrogen bonds have N...Cl distances in the range 3.1201   (8) – 3.4047   (8)   Å . In the single cation of the high-temperature structure, the NH hydrogen atoms are disordered into the average of the two low-temperature positions and the N...Cl hydrogen bond distances are in the range 3.1570   (15) – 3.3323   (18)   Å . At both temperatures, the methoxy group is nearly coplanar with the rest of the molecule, with the C — C — O — C torsion angles being − 7.0   (2) ° at 250   K and − 6.94   (12) and − 9.35   (12) ° at 100   K. In the extended orthorhombic structure, (001) hydrogen-bonded sheets occur; in the monoclinic structure, the sheets propagate in the (010) plane.
Source: Acta Crystallographica Section E - Category: Chemistry Authors: Tags: crystal structure 4-alkoxyacetanilides 4-alkoxyanilinium salts nonsteroidal analgesics mechanisms of toxicity research communications Source Type: research