Crystal structure of 2-pentyloxybenzamide

In the nearly planar 2-pentyloxybenzamide molecule, there is an intramolecular N—H⋯O hydrogen bond involving one amide proton and the ether oxygen. In the crystal, pairs of N—H⋯O hydrogen bonds organize molecules into inversion dimers lying in two planes, (121) and (11).

In the title molecule, C 12 H 17 NO 2 , the amide NH 2 group is oriented toward the pentyloxy substituent and an intramolecular N-HÁ Á ÁO hydrogen bond is formed with the pentyloxy O atom. The benzene ring forms dihedral angles of 2.93 (2) and 5.60 (2) with the amide group and the pentyloxy group mean planes, respectively. In the crystal, molecules are linked by pairs of N-HÁ Á ÁO hydrogen bonds, forming inversion dimers with their molecular planes parallel, but at an offset of 0.45 (1) Å to each other. These dimers are ordered into two types of symmetry-related columns extended along the a axis, with the mean plane of one set of dimers in a column approximately parallel to (121) and the other in a column approximately parallel to (121). The two planes form a dihedral angle of 85.31 (2) , and are linked via C-HÁ Á ÁO hydrogen bonds and C-HÁ Á Á interactions, forming a three-dimensional framework structure.
In our efforts to use 2-alkoxybenzamides as components in co-crystal formation (Aitipamula et al., 2012), we prepared the title compound, 2-pentyloxybenzamide, and report herein on its crystal structure. 2-Pentyloxybenzamide was first studied for its antipyretic and analgesic properties (Bavin et al., 1952;Macrae & Seymour, 1956). Afterwards, it was found to have antifungal activity and to be useful in the treatment of dermatomycosis (Simmonite & Tattersall, 1962;Coates et al., 1957). Under the name pentalamide, it is still used as an ingredient in antifungal agents for topical use.

Supramolecular features
In the crystal, molecules are linked by pairs of N-HÁ Á ÁO (N1-H1AÁ Á ÁO1) hydrogen bonds forming inversion dimers ( Fig. 2 and Table 1). These dimers form a nested network of molecules, made of two layers, (121) and (121), which form an angle of 85.31 (2) between their planes (Fig. 3). The dimers in the layers are linked by C-HÁ Á ÁO (C4-H4Á Á ÁO1) hydrogen bonds and C-HÁ Á Á interactions, forming a three-dimensional framework ( Fig. 3  A view of the molecular structure of the title molecule, with atom labelling. Displacement ellipsoids are shown at the 50% probability level. The intramolecular N-HÁ Á ÁO hydrogen bond is shown as a green dashed line (see Table 1 for details). Table 1 Hydrogen-bond geometry (Å , ).

Figure 2
A partial view of the crystal packing of the title compound. The hydrogen bonds are shown as green dashed lines [see Table 1 for details; symmetry codes:

Figure 3
A view of the crystal network formed by the layers of inversion dimers in the planes (121) in red, and (121) in blue. The hydrogen bonds are shown as green dashed lines (see Table 1 for details; H atoms have been omitted for clarity).
parallel layers are at a distance of 3.81 (3) Å from each other. Along the a axis the pairs are ordered in two symmetry-related columns. The plane of the benzene ring (C1-C6) of the 2pentyloxybenzamide forms an angle of 25.29 (2) with the column axis.  (Bugenhagen et al., 2012). For 2-propoxybenzamide, a homologue of the title compound, a similar formation of inversion-related molecular pairs in the crystal was reported, hence the two compounds exhibit a similar packing. The noticeable difference between the two compounds is the larger dihedral angle between the carboxamide group and the benzene ring in 2-propoxybenzamide, 12.41 (2) compared to 3.30 (15) in the title compound, 2-pentyloxybenzamide. Also, the parallel layers of molecules in the title compound are further apart [separated by 3.81 (3) Å ] than is found for a similar packing of 2-propoxybenzamide [3.69 (2) Å ]. Similarly, inversion-related pairs of molecules are formed by intermolecular (amide-amide) hydrogen bonding in 2-ethoxybenzamide and 3-hydroxy-2-methoxybenzamide. As 2ethoxybenzamide exhibits no intramolecular hydrogen bonding, the freed acceptor-donor sites are used for additional intermolecular hydrogen bonding with the adjacent molecule.

Synthesis and crystallization
The preparation of the title compound follows a Williamson ether synthesis using DMSO as solvent, analogous to a general procedure (Johnstone & Rose, 1979)