Cyclohexylammonium 4-methoxybenzoate

In the crystal of the title molecular salt, C6H14N+·C8H7O3 −, strong N—H⋯O hydrogen bonds are formed between the ammonium H atoms and the carboxylate O atoms. The resulting supramolecular structure is based on chains running in the [010] direction. The dihedral angle between the –CO2 group and the benzene ring is 8.94 (17)° and the methoxy C atom deviates by 1.374 Å from the ring.

In the crystal of the title molecular salt, C 6 H 14 N + ÁC 8 H 7 O 3 À , strong N-HÁ Á ÁO hydrogen bonds are formed between the ammonium H atoms and the carboxylate O atoms. The resulting supramolecular structure is based on chains running in the [010] direction. The dihedral angle between the -CO 2 group and the benzene ring is 8.94 (17) and the methoxy C atom deviates by 1.374 Å from the ring.

Comment
Our research deals with new dielectric-ferroelectric materials. Recent studies have revealed that organic salt compounds which have one or more amidogens probably have this kind of property (Fu et al., 2009;Zhang et al., 2008Zhang et al., , 2010Ye et al., 2006). Thus, we are searching for aromatic compounds containing amidogens having dielectric-ferroelectric properties (Wu et al., 2011). Unfortunately, the dielectric constant of the title compound as a function of temperature indicates that the permittivity is basically temperature-independent below the melting point of the salt (413 K -415 K). We have found that cyclohexylammonium 4-methoxybenzoate has no dielectric inhomogeneity from 80 K to 405 K. Herein, we describe the crystal structure of this compound.
The asymmetric unit of the title compound consists of a cyclohexylammonium cation, and a 4-methoxybenzoate anion ( Fig. 1). Strong N-H···O hydrogen bonds are formed between the H atoms of the ammonium group and the O atoms of the carboxylate group, which also make great contribution to the stability of the crystal structure, linking the cations and anions into chains along the b axis (Table 1 and Fig. 2).

Experimental
The title compound was obtained by addition of para-methoxybenzoic acid (1.52 g, 0.01 mol) to a solution of cyclohexylamine (1.02 g, 0.01 mol) in methanol, in the stoichiometric ratio 1:1. Good quality single crystals were obtained by slow evaporation after two days (the chemical yield is 45%).

Refinement
All H atoms attached to C atoms were fixed geometrically and treated as riding with C-H = 0.97 Å (methylene), C-H = 0.96 Å (methyl), C-H = 0.98 Å (methine), and C-H = 0.93 Å (aromatic), and with U iso (H) = 1.2U eq (C except methyl) or U iso (H) = 1.5U eq (C of methyl). The H atoms bonded to N1 were refined as riding atoms with N-H = 0.89 Å, and U iso (H) = 1.5U eq (N1). Since no significant anomalous dispersion is expected for this formula, measured Friedel pairs (1408) were merged. Fig. 1. The molecular structure of the title compound, with displacement ellipsoids at the 30% probability level.