Cyclo­hexane­carboxamide

The title compound, C₇H₁₃NO, forms R²₂(8) N—H...O hy­dro­gen-bonded dimers and C4 N—H...O-linked chains, which are further stabilized by a C—H...O 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—H...O 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].

S1. Comment

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.

S2. Experimental

The title compound was prepared as described by Lumsden (1905). The product was recrystallized from ethanol using a slow evaporation technique at room temperature with a 71% yield of colourless plate-like crystals [m.p. 458–460 K (literature value 459–460.5 K; McElvain & Starn, 1955)]. Spectroscopic analysis: ¹H NMR (300 MHz, CDCl₃, Me₄Si): δ 5.69 (1H, s, N—H), 5.52 (1H, s, N—H), 2.15 (1H, tt, J = 3.5 and 11.6 Hz, H1), 1.93–1.69 (5H, m, H2, H3, H4, H5, H6), 1.48–1.30 (5H, m, H2, H3, H4, H5, H6) p.p.m.; ¹³C NMR (75 MHz, CDCl₃, Me₄Si): δ 178.7 (C6), 44.8 (C1), 297 (C2, C6), 25.7 (C3, C5), 25.6 (C4) p.p.m.; IR (Medium?): ν_max 3337 (m, b, N—H), 3154 (m, b, N—H), 2927 (m, sh, C—H), 2851 (m, sh, C—H), 1635 (s, C═O), 1428 (s, C—N), 1344 (w, sh), 1285 (m, sh), 1230 (m, sh), 1154 (m, sh), 666 (s) cm^-1.

S3. Refinement

All H atoms were positioned geometrically and allowed to ride on their parent atoms [C—H = 1.00 (CH) or 0.99 Å (CH₂), and N—H = 0.88 Å (NH₂), and U_iso(H) = 1.2U_eq(C,N)].

Computing details

Data collection: APEX2 (Bruker, 2005); cell refinement: APEX2 (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and SCHAKAL99 (Keller, 1999); software used to prepare material for publication: WinGX (Farrugia, 1999) and PLATON (Spek, 2009).

Figures

Fig. 1. The molecular structure of (I), showing the atomic numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.

Fig. 2. The intermolecular N—H···O and C—H···O hydrogen-bonding network (dashed lines) in the structure of (I), where molecules are connected to each other to form dimers and chains. The combination of these results in a hydrogen-bonded sheet running parallel to (011). All H atoms not involved in these interactions have been omitted for clarity. [Symmetry codes: (i) x, y, z; (ii) -x + 1/2, -y + 3/2, -z + 1; (iii) -x + 1/2, y - 1/2, -z + 1; (iv) x, -y + 1, z + 1/2; (v) -x + 1/2, y + 1/2, -z + 3/2; (vi) x, -y + 2, z + 1/2; (vii) x, y, z; (viii) -x + 1/2, -y + 3/2, -z + 2.]

Cyclohexanecarboxamide

Crystal data

C7H13NO	F(000) = 560
Mr = 127.18	Dx = 1.115 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 2522 reflections
a = 24.624 (3) Å	θ = 2.2–28.2°
b = 6.6934 (9) Å	µ = 0.07 mm^−1
c = 9.4030 (13) Å	T = 173 K
β = 102.088 (3)°	Plate, colourless
V = 1515.4 (3) Å^3	0.48 × 0.37 × 0.10 mm
Z = 8

Data collection

Bruker APEXII CCD area-detector diffractometer	1440 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.068
Graphite monochromator	θmax = 28.0°, θmin = 1.7°
ϕ and ω scans	h = −32→28
9664 measured reflections	k = −8→8
1828 independent reflections	l = −12→12

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.056	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.143	H-atom parameters constrained
S = 1.05	w = 1/[σ^2(Fo^2) + (0.0709P)^2 + 0.6992P] where P = (Fo^2 + 2Fc^2)/3
1828 reflections	(Δ/σ)max < 0.001
82 parameters	Δρmax = 0.28 e Å^−3
0 restraints	Δρmin = −0.16 e Å^−3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
C1	0.19171 (6)	0.5284 (2)	0.51551 (14)	0.0226 (3)
C2	0.14896 (6)	0.3714 (2)	0.52825 (15)	0.0263 (3)
H2	0.1491	0.3504	0.6336	0.032*
C3	0.16303 (6)	0.1743 (2)	0.4640 (2)	0.0354 (4)
H3A	0.1655	0.1952	0.3613	0.043*
H3B	0.1998	0.1276	0.5179	0.043*
C4	0.11965 (7)	0.0152 (2)	0.4715 (2)	0.0438 (5)
H4A	0.1288	−0.1079	0.4232	0.053*
H4B	0.1203	−0.0172	0.5746	0.053*
C5	0.06229 (7)	0.0844 (3)	0.3991 (2)	0.0444 (5)
H5A	0.0348	−0.0179	0.4127	0.053*
H5B	0.0603	0.0994	0.2933	0.053*
C6	0.04791 (7)	0.2807 (3)	0.4606 (3)	0.0522 (5)
H6A	0.0454	0.2616	0.5634	0.063*
H6B	0.0112	0.3260	0.4059	0.063*
C7	0.09113 (7)	0.4401 (2)	0.4519 (2)	0.0414 (4)
H7A	0.0815	0.5645	0.4979	0.050*
H7B	0.0910	0.4694	0.3486	0.050*
N1	0.21894 (5)	0.61139 (19)	0.63692 (12)	0.0285 (3)
H1A	0.2439	0.7044	0.6337	0.034*
H1B	0.2121	0.5738	0.7211	0.034*
O1	0.20016 (4)	0.57749 (15)	0.39458 (10)	0.0275 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0252 (7)	0.0248 (7)	0.0192 (6)	0.0012 (5)	0.0077 (5)	−0.0012 (5)
C2	0.0306 (8)	0.0292 (7)	0.0208 (7)	−0.0061 (6)	0.0094 (6)	−0.0008 (5)
C3	0.0284 (8)	0.0242 (8)	0.0537 (10)	0.0021 (6)	0.0088 (7)	0.0015 (7)
C4	0.0433 (10)	0.0237 (8)	0.0644 (12)	−0.0036 (7)	0.0116 (9)	0.0025 (7)
C5	0.0365 (10)	0.0343 (9)	0.0626 (12)	−0.0110 (7)	0.0109 (8)	−0.0052 (8)
C6	0.0282 (9)	0.0417 (10)	0.0902 (16)	−0.0058 (7)	0.0204 (9)	−0.0088 (10)
C7	0.0289 (8)	0.0277 (8)	0.0697 (12)	0.0002 (6)	0.0148 (8)	−0.0046 (8)
N1	0.0354 (7)	0.0338 (7)	0.0171 (6)	−0.0107 (5)	0.0074 (5)	−0.0014 (5)
O1	0.0355 (6)	0.0317 (6)	0.0170 (5)	−0.0080 (4)	0.0096 (4)	−0.0015 (4)

Geometric parameters (Å, º)

C1—O1	1.2424 (16)	C4—H4B	0.9900
C1—N1	1.3195 (18)	C5—C6	1.507 (3)
C1—C2	1.5099 (19)	C5—H5A	0.9900
C2—C3	1.521 (2)	C5—H5B	0.9900
C2—C7	1.525 (2)	C6—C7	1.521 (2)
C2—H2	1.0000	C6—H6A	0.9900
C3—C4	1.520 (2)	C6—H6B	0.9900
C3—H3A	0.9900	C7—H7A	0.9900
C3—H3B	0.9900	C7—H7B	0.9900
C4—C5	1.507 (3)	N1—H1A	0.8800
C4—H4A	0.9900	N1—H1B	0.8800
O1—C1—N1	121.89 (13)	C4—C5—C6	111.58 (16)
O1—C1—C2	120.66 (12)	C4—C5—H5A	109.3
N1—C1—C2	117.44 (11)	C6—C5—H5A	109.3
C1—C2—C3	110.59 (11)	C4—C5—H5B	109.3
C1—C2—C7	110.51 (12)	C6—C5—H5B	109.3
C3—C2—C7	110.02 (13)	H5A—C5—H5B	108.0
C1—C2—H2	108.6	C5—C6—C7	111.55 (14)
C3—C2—H2	108.6	C5—C6—H6A	109.3
C7—C2—H2	108.6	C7—C6—H6A	109.3
C4—C3—C2	111.62 (13)	C5—C6—H6B	109.3
C4—C3—H3A	109.3	C7—C6—H6B	109.3
C2—C3—H3A	109.3	H6A—C6—H6B	108.0
C4—C3—H3B	109.3	C6—C7—C2	110.97 (15)
C2—C3—H3B	109.3	C6—C7—H7A	109.4
H3A—C3—H3B	108.0	C2—C7—H7A	109.4
C5—C4—C3	111.40 (14)	C6—C7—H7B	109.4
C5—C4—H4A	109.3	C2—C7—H7B	109.4
C3—C4—H4A	109.3	H7A—C7—H7B	108.0
C5—C4—H4B	109.3	C1—N1—H1A	120.0
C3—C4—H4B	109.3	C1—N1—H1B	120.0
H4A—C4—H4B	108.0	H1A—N1—H1B	120.0
O1—C1—C2—C3	59.46 (18)	C3—C4—C5—C6	−54.5 (2)
N1—C1—C2—C3	−121.17 (14)	C4—C5—C6—C7	55.1 (2)
O1—C1—C2—C7	−62.62 (18)	C5—C6—C7—C2	−56.1 (2)
N1—C1—C2—C7	116.75 (15)	C1—C2—C7—C6	178.50 (14)
C1—C2—C3—C4	−178.32 (13)	C3—C2—C7—C6	56.09 (19)
C7—C2—C3—C4	−55.96 (18)	C2—C1—C1^i—C2^i	−90.99 (16)
C2—C3—C4—C5	55.4 (2)	N1—C1—C2—H2	−2.2

Symmetry code: (i) x, −y+1, z+1/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···O1^ii	0.88	2.06	2.9394 (16)	175
N1—H1B···O1^i	0.88	1.99	2.8549 (15)	166
C2—H2···O1^i	1.00	2.56	3.4283 (17)	145

Symmetry codes: (i) x, −y+1, z+1/2; (ii) −x+1/2, −y+3/2, −z+1.