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

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

Rao M. Uppu; Sainath Babu; Frank R. Fronczek

DOI: PMID:

Abstract

At room temperature, the title salt, C7H10NO+·Cl−, is ortho­rhom­bic, space group Pbca with Z′ = 1, as previously reported [Zhao (2009[Zhao, M. M. (2009). Acta Cryst. E65, o2378.]). Acta Cryst. E65, o2378]. Between 250 and 200 K, there is a solid-state phase transition to a twinned monoclinic P21/c structure with Z′ = 2. 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.

Keywords

crystal structure ; 4-alk­oxy­acetanilides ; 4-alk­oxy­anilinium salts ; nonsteroidal analgesics ; mechanisms of toxicity

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4-Methoxyaniline hydrochloride

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