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organic compounds
The title compound, C7H13NO, forms R22(8) N—HO hydrogen-bonded dimers and C4 N—HO-linked chains, which are further stabilized by a C—HO interaction. The combination of these interactions results in a hydrogen-bonded network parallel to (100), with a motif that can be described by the secondary graph set R46(16). The existence of the same hydrogen-bonding motif in 1-phenylcyclopentanecarboxamide and 1-(2-bromophenyl)cyclohexanecarboxamide [Lemmerer & Michael (2008). CrystEngComm, 10, 95–102 indicates that replacing the H atom on position 1 with a more bulky group does not necessarily disrupt the observed hydrogen-bonding pattern. The presence of a C—HO interaction to stabilize the R46(16) network does, however, seem to be required. In addition, the title compound is isomorphous with a previously published structure of cyclopentanecarboxamide [Winter et al. (1981). Acta Cryst. B37, 2183–2185].
The hydrogen-bonding capabilities of amides have been extensively researched (Taylor et al., 1984; Leiserowitz & Schmidt, 1969), and they have been exploited directly, or as precursors, in crystal engineering and the pharmaceutical industries (Reddy et al., 2006), to name but a few. In addition, a systematic study of the effect of different 2,6 substitution on the structure of phenylamides and their consequent thermal behaviour has been published (Omondi et al., 2005), as well as a similar structural study of a series of slightly more complex 1-arylcycloalkanecarboxamides (Lemmerer & Michael, 2008). In a study of symmetric and asymmetric imides and their polymorphs, the title compound, (I), was synthesized as a precursor for imide synthesis.
Compound (I) crystallizes in space group C2/c with one molecule in the asymmetric unit (Fig. 1). The molecule adopts a chair conformation in which the amide group is rotated to be almost perpendicular to the cyclohexyl ring; atom N1 is orientated such that it lies almost eclipsed relative to atom H2, the N1—C1—C2—H2 torsion angle being -2.2°.
The structure of (I) contains two distinctive types of N—H···O hydrogen bonds. One of these [N1—H1A···O1i; symmetry code (i) -x + 1/2, -y + 3/2, -z + 1; Fig. 2 and Table 1] is a hydrogen bond between two amide molecules to form an R22(8) dimer (Etter et al., 1990; Bernstein et al., 1995), with the molecules related to each other through a centre of inversion. The other [N1—H1B···O1ii; symmetry code: (ii) x, -y + 1, z + 1/2; Fig. 2 and Table 1] is an interaction along the c axis to form a C4 hydrogen-bonded chain, in which the molecules are related to each other by a c-glide plane. This C4 chain is further stabilized by a C—H···O interaction (C2—H2···O1ii; Fig. 2 and Table 1). The combination of the two N—H···O interactions results in the hydrogen-bonded dimers being almost perpendicular to each other [C1—C2···C2ii—C1ii = -90.99 (16)°] and in the formation of a hydrogen-bonded network parallel to (011). The combination of the two hydrogen bonds also results in a motif that can be described by the secondary graph set R46(16).
A search of the Cambridge Structural Database (CSD; Version 5.30, November 2008 release; Allen, 2002) led to the discovery of the isomorphous structure of cyclopentanecarboxamide (CSD refcode BARFEF; Winter et al., 1981), which has an identical hydrogen-bonding pattern despite the presence of disorder in the five-membered ring. The R46(16) motif can also be found in the structures of 1-phenylcyclopentanecarboxamide and 1-(2-bromophenyl)cyclohexanecarboxamide, indicating that replacing atom H2 with a more bulky group does not necessarily disrupt this hydrogen-bond pattern (Lemmerer & Michael, 2008). However, a C—H···O interaction does seem to be required, as it is present in all four structures. In the case of 1-phenylcyclopentanecarboxamide and 1-(2-bromophenyl)cyclohexanecarboxamide, the C—H···O interaction occurs between the amide O atom and one of the ring CH2 groups.