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Hexamethylenetetramine and
rac-
trans-1,2-cyclohexanedicarboxylic acid crystallize in a 1:1 ratio as a neutral molecular adduct, C
6H
12N
4·C
8H
12O
4. Two dicarboxylic acid molecules and two tetramine molecules form a hydrogen-bonded ring, in the shape of a rhombus, which lies on a crystallographic twofold axis bisecting the two diacid molecules. The O-H
N hydrogen bonds have lengths 2.6808 (19) and 2.6518 (19) Å, and, in each ring, both acid molecules have the same handedness.
Supporting information
CCDC reference: 251308
All reagents and solvents used were commercially available and were used as received without further purification. An ethanol solution (15 ml) of CDA (0.172 g, 1.0 mmol) was added to a stirred solution (5 ml) of HMT (0.100 g, 1.0 mmol) and the reaction mixture stirred for 1 hr. The resulting colorless solution was allowed to stand in air at room temperature for 2 d, yielding colorless crystals of (I) suitable for X-ray analysis. IR spectra for the product were obtained in the 4000–400 cm−1 range in KBr pellets on a Nicolet Nexus 670 F T—IR spectrophotometer. (The –OH stretching frequency νOH around 3560 cm−1 is very broad compared with the sharp –OH band in the spectrum for CDA. Similarly, the sharp bands of –CN stretching and –NCN bond + ring deformation around 1440 cm−1 and 1540 cm−1 are also found to become one broad band in the adduct).
The absolute structure could not be determined, and Friedel equivalents were averaged. H atoms on C atoms were treated as riding in idealized positions, with C—H distances in the range 0.95–0.99 Å, depending on atom type. The coordinates of H atoms on O atoms were refined. Displacement parameters for all H atoms were assigned as Uiso(H) = 1.2Ueq of the attached atom.
Data collection: COLLECT (Nonius, 2000); cell refinement: HKL SCALEPACK (Otwinowski & Minor 1997); data reduction: HKL DENZO (Otwinowski & Minor 1997) and SCALEPACK; program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXL97.
Hexamethylenetetramine–rac-
trans-1,2-cyclohexanedicarboxylic acid (1:1)
top
Crystal data top
C6H12N4·C8H12O4 | F(000) = 1344 |
Mr = 312.37 | Dx = 1.296 Mg m−3 |
Orthorhombic, Aba2 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: A 2 -2ac | Cell parameters from 3171 reflections |
a = 11.990 (3) Å | θ = 2.5–33.1° |
b = 11.814 (3) Å | µ = 0.10 mm−1 |
c = 22.606 (6) Å | T = 102 K |
V = 3202.1 (14) Å3 | Rectangular prism, colorless |
Z = 8 | 0.25 × 0.25 × 0.12 mm |
Data collection top
Nonius KappaCCD (with Oxford Cryostream) diffractometer | 2652 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.033 |
Graphite monochromator | θmax = 33.1°, θmin = 2.5° |
ω scans with κ offsets | h = −18→18 |
17655 measured reflections | k = −18→18 |
3119 independent reflections | l = −34→34 |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.041 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.097 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.04 | w = 1/[σ2(Fo2) + (0.0511P)2 + 0.5607P] where P = (Fo2 + 2Fc2)/3 |
3119 reflections | (Δ/σ)max < 0.001 |
205 parameters | Δρmax = 0.32 e Å−3 |
1 restraint | Δρmin = −0.27 e Å−3 |
Crystal data top
C6H12N4·C8H12O4 | V = 3202.1 (14) Å3 |
Mr = 312.37 | Z = 8 |
Orthorhombic, Aba2 | Mo Kα radiation |
a = 11.990 (3) Å | µ = 0.10 mm−1 |
b = 11.814 (3) Å | T = 102 K |
c = 22.606 (6) Å | 0.25 × 0.25 × 0.12 mm |
Data collection top
Nonius KappaCCD (with Oxford Cryostream) diffractometer | 2652 reflections with I > 2σ(I) |
17655 measured reflections | Rint = 0.033 |
3119 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.041 | 1 restraint |
wR(F2) = 0.097 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.04 | Δρmax = 0.32 e Å−3 |
3119 reflections | Δρmin = −0.27 e Å−3 |
205 parameters | |
Special details top
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 (Å2) top | x | y | z | Uiso*/Ueq | |
O1 | 0.43824 (11) | 0.29207 (10) | 0.22175 (6) | 0.0225 (3) | |
H1O | 0.396 (2) | 0.275 (2) | 0.2526 (13) | 0.034* | |
O2 | 0.36053 (11) | 0.46191 (11) | 0.23555 (6) | 0.0247 (3) | |
O3 | 0.30918 (11) | 0.39861 (12) | 0.50944 (6) | 0.0252 (3) | |
H3O | 0.296 (2) | 0.352 (2) | 0.4769 (13) | 0.038* | |
O4 | 0.48849 (11) | 0.35855 (12) | 0.49274 (6) | 0.0272 (3) | |
N1 | 0.11509 (11) | 0.23047 (12) | 0.34622 (7) | 0.0154 (3) | |
N2 | 0.24139 (12) | 0.07814 (11) | 0.37716 (6) | 0.0151 (3) | |
N3 | 0.30955 (11) | 0.22983 (11) | 0.31311 (6) | 0.0136 (2) | |
N4 | 0.26459 (11) | 0.26894 (11) | 0.41666 (6) | 0.0148 (3) | |
C1 | 0.12582 (13) | 0.10846 (13) | 0.36051 (8) | 0.0159 (3) | |
H1A | 0.0750 | 0.0896 | 0.3936 | 0.019* | |
H1B | 0.1030 | 0.0631 | 0.3257 | 0.019* | |
C2 | 0.31559 (14) | 0.10774 (13) | 0.32809 (8) | 0.0155 (3) | |
H2A | 0.2950 | 0.0625 | 0.2929 | 0.019* | |
H2B | 0.3933 | 0.0882 | 0.3389 | 0.019* | |
C3 | 0.33904 (13) | 0.29520 (14) | 0.36651 (8) | 0.0153 (3) | |
H3A | 0.3344 | 0.3771 | 0.3575 | 0.018* | |
H3B | 0.4170 | 0.2779 | 0.3778 | 0.018* | |
C4 | 0.14829 (13) | 0.29488 (14) | 0.39864 (8) | 0.0157 (3) | |
H4A | 0.0971 | 0.2767 | 0.4317 | 0.019* | |
H4B | 0.1417 | 0.3768 | 0.3902 | 0.019* | |
C5 | 0.19139 (14) | 0.25643 (15) | 0.29739 (7) | 0.0168 (3) | |
H5A | 0.1852 | 0.3377 | 0.2872 | 0.020* | |
H5B | 0.1696 | 0.2120 | 0.2621 | 0.020* | |
C6 | 0.27195 (15) | 0.14611 (14) | 0.42904 (7) | 0.0176 (3) | |
H6A | 0.3491 | 0.1271 | 0.4412 | 0.021* | |
H6B | 0.2216 | 0.1271 | 0.4623 | 0.021* | |
C7 | 0.42306 (13) | 0.39993 (14) | 0.20842 (7) | 0.0153 (3) | |
C8 | 0.48856 (13) | 0.43654 (14) | 0.15431 (7) | 0.0145 (3) | |
H8 | 0.5615 | 0.3955 | 0.1540 | 0.017* | |
C9 | 0.42250 (16) | 0.40338 (16) | 0.09842 (8) | 0.0212 (3) | |
H9A | 0.4095 | 0.3206 | 0.0983 | 0.025* | |
H9B | 0.3490 | 0.4416 | 0.0988 | 0.025* | |
C10 | 0.48636 (19) | 0.43710 (19) | 0.04264 (8) | 0.0298 (4) | |
H10A | 0.5564 | 0.3930 | 0.0403 | 0.036* | |
H10B | 0.4409 | 0.4188 | 0.0074 | 0.036* | |
C11 | 0.41698 (14) | 0.40626 (14) | 0.52135 (7) | 0.0152 (3) | |
C12 | 0.44029 (13) | 0.47767 (14) | 0.57575 (7) | 0.0139 (3) | |
H12 | 0.3881 | 0.5437 | 0.5758 | 0.017* | |
C13 | 0.41838 (15) | 0.40650 (14) | 0.63174 (8) | 0.0189 (3) | |
H13A | 0.3399 | 0.3803 | 0.6319 | 0.023* | |
H13B | 0.4672 | 0.3389 | 0.6315 | 0.023* | |
C14 | 0.44094 (17) | 0.47615 (18) | 0.68738 (8) | 0.0252 (4) | |
H14A | 0.3867 | 0.5392 | 0.6896 | 0.030* | |
H14B | 0.4304 | 0.4278 | 0.7227 | 0.030* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O1 | 0.0279 (6) | 0.0198 (6) | 0.0198 (6) | 0.0013 (5) | 0.0113 (5) | 0.0032 (5) |
O2 | 0.0316 (7) | 0.0214 (6) | 0.0212 (6) | 0.0000 (5) | 0.0127 (5) | −0.0015 (5) |
O3 | 0.0177 (6) | 0.0355 (7) | 0.0225 (7) | −0.0035 (5) | −0.0006 (5) | −0.0146 (6) |
O4 | 0.0211 (6) | 0.0379 (8) | 0.0226 (7) | 0.0008 (6) | 0.0022 (5) | −0.0154 (6) |
N1 | 0.0120 (6) | 0.0165 (6) | 0.0177 (6) | −0.0005 (5) | −0.0001 (5) | 0.0002 (5) |
N2 | 0.0175 (6) | 0.0117 (5) | 0.0162 (6) | −0.0004 (5) | 0.0014 (5) | 0.0013 (5) |
N3 | 0.0143 (6) | 0.0135 (6) | 0.0129 (6) | 0.0000 (5) | 0.0016 (5) | 0.0005 (5) |
N4 | 0.0139 (6) | 0.0171 (6) | 0.0134 (6) | −0.0030 (5) | −0.0001 (5) | −0.0037 (5) |
C1 | 0.0147 (7) | 0.0139 (6) | 0.0191 (8) | −0.0040 (5) | 0.0009 (6) | −0.0024 (6) |
C2 | 0.0153 (7) | 0.0128 (6) | 0.0185 (7) | 0.0018 (6) | 0.0045 (6) | −0.0027 (6) |
C3 | 0.0131 (6) | 0.0158 (7) | 0.0170 (7) | −0.0045 (5) | 0.0020 (6) | −0.0011 (6) |
C4 | 0.0120 (6) | 0.0144 (6) | 0.0208 (8) | −0.0012 (6) | 0.0030 (6) | −0.0047 (6) |
C5 | 0.0157 (7) | 0.0202 (7) | 0.0145 (7) | 0.0001 (6) | −0.0020 (6) | 0.0048 (6) |
C6 | 0.0217 (8) | 0.0178 (7) | 0.0133 (7) | −0.0008 (6) | −0.0007 (6) | 0.0036 (6) |
C7 | 0.0167 (7) | 0.0193 (7) | 0.0098 (7) | −0.0043 (6) | 0.0009 (6) | −0.0025 (5) |
C8 | 0.0162 (7) | 0.0175 (7) | 0.0097 (6) | −0.0029 (6) | 0.0032 (5) | −0.0012 (6) |
C9 | 0.0241 (8) | 0.0262 (8) | 0.0134 (7) | −0.0110 (7) | −0.0007 (6) | −0.0030 (7) |
C10 | 0.0410 (11) | 0.0383 (11) | 0.0100 (7) | −0.0138 (9) | 0.0033 (7) | −0.0049 (7) |
C11 | 0.0188 (7) | 0.0154 (7) | 0.0115 (7) | −0.0036 (6) | 0.0003 (5) | −0.0002 (5) |
C12 | 0.0140 (6) | 0.0162 (7) | 0.0114 (6) | −0.0019 (6) | 0.0012 (5) | −0.0019 (5) |
C13 | 0.0220 (8) | 0.0227 (7) | 0.0122 (7) | −0.0066 (7) | 0.0024 (6) | 0.0004 (6) |
C14 | 0.0309 (10) | 0.0329 (10) | 0.0117 (7) | −0.0088 (8) | 0.0040 (7) | −0.0007 (7) |
Geometric parameters (Å, º) top
O1—C7 | 1.322 (2) | C4—H4B | 0.9900 |
O1—H1O | 0.88 (3) | C5—H5A | 0.9900 |
O2—C7 | 1.214 (2) | C5—H5B | 0.9900 |
O3—C11 | 1.323 (2) | C6—H6A | 0.9900 |
O3—H3O | 0.93 (3) | C6—H6B | 0.9900 |
O4—C11 | 1.213 (2) | C7—C8 | 1.516 (2) |
N1—C4 | 1.464 (2) | C8—C8i | 1.524 (3) |
N1—C5 | 1.466 (2) | C8—C9 | 1.542 (2) |
N1—C1 | 1.483 (2) | C8—H8 | 1.0000 |
N2—C2 | 1.464 (2) | C9—C10 | 1.528 (3) |
N2—C6 | 1.468 (2) | C9—H9A | 0.9900 |
N2—C1 | 1.480 (2) | C9—H9B | 0.9900 |
N3—C3 | 1.476 (2) | C10—C10i | 1.522 (4) |
N3—C2 | 1.483 (2) | C10—H10A | 0.9900 |
N3—C5 | 1.494 (2) | C10—H10B | 0.9900 |
N4—C3 | 1.476 (2) | C11—C12 | 1.517 (2) |
N4—C6 | 1.481 (2) | C12—C12i | 1.526 (3) |
N4—C4 | 1.485 (2) | C12—C13 | 1.542 (2) |
C1—H1A | 0.9900 | C12—H12 | 1.0000 |
C1—H1B | 0.9900 | C13—C14 | 1.527 (3) |
C2—H2A | 0.9900 | C13—H13A | 0.9900 |
C2—H2B | 0.9900 | C13—H13B | 0.9900 |
C3—H3A | 0.9900 | C14—C14i | 1.524 (4) |
C3—H3B | 0.9900 | C14—H14A | 0.9900 |
C4—H4A | 0.9900 | C14—H14B | 0.9900 |
| | | |
C7—O1—H1O | 108.4 (17) | N4—C6—H6A | 109.3 |
C11—O3—H3O | 111.2 (17) | N2—C6—H6B | 109.3 |
C4—N1—C5 | 109.34 (13) | N4—C6—H6B | 109.3 |
C4—N1—C1 | 107.78 (13) | H6A—C6—H6B | 107.9 |
C5—N1—C1 | 108.26 (13) | O2—C7—O1 | 123.45 (15) |
C2—N2—C6 | 108.84 (13) | O2—C7—C8 | 123.72 (15) |
C2—N2—C1 | 108.56 (13) | O1—C7—C8 | 112.79 (14) |
C6—N2—C1 | 107.73 (13) | C7—C8—C8i | 111.95 (11) |
C3—N3—C2 | 108.08 (13) | C7—C8—C9 | 108.82 (13) |
C3—N3—C5 | 108.16 (12) | C8i—C8—C9 | 110.02 (12) |
C2—N3—C5 | 107.77 (12) | C7—C8—H8 | 108.7 |
C3—N4—C6 | 108.37 (13) | C8i—C8—H8 | 108.7 |
C3—N4—C4 | 108.30 (13) | C9—C8—H8 | 108.7 |
C6—N4—C4 | 108.07 (12) | C10—C9—C8 | 110.65 (14) |
N2—C1—N1 | 111.84 (12) | C10—C9—H9A | 109.5 |
N2—C1—H1A | 109.2 | C8—C9—H9A | 109.5 |
N1—C1—H1A | 109.2 | C10—C9—H9B | 109.5 |
N2—C1—H1B | 109.2 | C8—C9—H9B | 109.5 |
N1—C1—H1B | 109.2 | H9A—C9—H9B | 108.1 |
H1A—C1—H1B | 107.9 | C10i—C10—C9 | 111.24 (15) |
N2—C2—N3 | 112.06 (12) | C10i—C10—H10A | 109.4 |
N2—C2—H2A | 109.2 | C9—C10—H10A | 109.4 |
N3—C2—H2A | 109.2 | C10i—C10—H10B | 109.4 |
N2—C2—H2B | 109.2 | C9—C10—H10B | 109.4 |
N3—C2—H2B | 109.2 | H10A—C10—H10B | 108.0 |
H2A—C2—H2B | 107.9 | O4—C11—O3 | 123.38 (16) |
N3—C3—N4 | 111.92 (12) | O4—C11—C12 | 124.08 (16) |
N3—C3—H3A | 109.2 | O3—C11—C12 | 112.51 (14) |
N4—C3—H3A | 109.2 | C11—C12—C12i | 111.41 (11) |
N3—C3—H3B | 109.2 | C11—C12—C13 | 109.31 (13) |
N4—C3—H3B | 109.2 | C12i—C12—C13 | 110.39 (11) |
H3A—C3—H3B | 107.9 | C11—C12—H12 | 108.6 |
N1—C4—N4 | 111.74 (13) | C12i—C12—H12 | 108.6 |
N1—C4—H4A | 109.3 | C13—C12—H12 | 108.6 |
N4—C4—H4A | 109.3 | C14—C13—C12 | 110.61 (14) |
N1—C4—H4B | 109.3 | C14—C13—H13A | 109.5 |
N4—C4—H4B | 109.3 | C12—C13—H13A | 109.5 |
H4A—C4—H4B | 107.9 | C14—C13—H13B | 109.5 |
N1—C5—N3 | 111.63 (13) | C12—C13—H13B | 109.5 |
N1—C5—H5A | 109.3 | H13A—C13—H13B | 108.1 |
N3—C5—H5A | 109.3 | C14i—C14—C13 | 111.33 (13) |
N1—C5—H5B | 109.3 | C14i—C14—H14A | 109.4 |
N3—C5—H5B | 109.3 | C13—C14—H14A | 109.4 |
H5A—C5—H5B | 108.0 | C14i—C14—H14B | 109.4 |
N2—C6—N4 | 111.73 (13) | C13—C14—H14B | 109.4 |
N2—C6—H6A | 109.3 | H14A—C14—H14B | 108.0 |
| | | |
C2—N2—C1—N1 | −58.26 (17) | C2—N3—C5—N1 | 58.89 (17) |
C6—N2—C1—N1 | 59.46 (17) | C2—N2—C6—N4 | 58.40 (17) |
C4—N1—C1—N2 | −59.52 (17) | C1—N2—C6—N4 | −59.14 (17) |
C5—N1—C1—N2 | 58.64 (17) | C3—N4—C6—N2 | −58.21 (17) |
C6—N2—C2—N3 | −58.47 (17) | C4—N4—C6—N2 | 58.95 (18) |
C1—N2—C2—N3 | 58.53 (16) | O2—C7—C8—C8i | 26.6 (2) |
C3—N3—C2—N2 | 58.10 (17) | O1—C7—C8—C8i | −155.58 (16) |
C5—N3—C2—N2 | −58.57 (17) | O2—C7—C8—C9 | −95.17 (19) |
C2—N3—C3—N4 | −58.10 (16) | O1—C7—C8—C9 | 82.61 (17) |
C5—N3—C3—N4 | 58.32 (16) | C7—C8—C9—C10 | −179.13 (16) |
C6—N4—C3—N3 | 58.38 (17) | C8i—C8—C9—C10 | 57.9 (2) |
C4—N4—C3—N3 | −58.62 (16) | C8—C9—C10—C10i | −56.1 (3) |
C5—N1—C4—N4 | −58.42 (17) | O4—C11—C12—C12i | 23.5 (2) |
C1—N1—C4—N4 | 59.04 (16) | O3—C11—C12—C12i | −158.52 (16) |
C3—N4—C4—N1 | 58.22 (16) | O4—C11—C12—C13 | −98.8 (2) |
C6—N4—C4—N1 | −58.98 (17) | O3—C11—C12—C13 | 79.21 (17) |
C4—N1—C5—N3 | 58.12 (17) | C11—C12—C13—C14 | −179.90 (15) |
C1—N1—C5—N3 | −59.04 (17) | C12i—C12—C13—C14 | 57.2 (2) |
C3—N3—C5—N1 | −57.73 (17) | C12—C13—C14—C14i | −56.0 (2) |
Symmetry code: (i) −x+1, −y+1, z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1O···N3 | 0.88 (3) | 1.80 (3) | 2.6808 (19) | 175 (3) |
O3—H3O···N4 | 0.93 (3) | 1.72 (3) | 2.6518 (19) | 177 (3) |
C1—H1A···O4ii | 0.99 | 2.54 | 3.435 (2) | 150 |
C1—H1B···O2iii | 0.99 | 2.40 | 3.317 (2) | 153 |
C2—H2A···O2iii | 0.99 | 2.56 | 3.436 (2) | 147 |
C3—H3A···N2iv | 0.99 | 2.58 | 3.487 (2) | 152 |
C3—H3B···N1v | 0.99 | 2.48 | 3.355 (2) | 147 |
C4—H4A···O4ii | 0.99 | 2.48 | 3.388 (2) | 152 |
Symmetry codes: (ii) x−1/2, −y+1/2, z; (iii) −x+1/2, y−1/2, z; (iv) −x+1/2, y+1/2, z; (v) x+1/2, −y+1/2, z. |
Experimental details
Crystal data |
Chemical formula | C6H12N4·C8H12O4 |
Mr | 312.37 |
Crystal system, space group | Orthorhombic, Aba2 |
Temperature (K) | 102 |
a, b, c (Å) | 11.990 (3), 11.814 (3), 22.606 (6) |
V (Å3) | 3202.1 (14) |
Z | 8 |
Radiation type | Mo Kα |
µ (mm−1) | 0.10 |
Crystal size (mm) | 0.25 × 0.25 × 0.12 |
|
Data collection |
Diffractometer | Nonius KappaCCD (with Oxford Cryostream) diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 17655, 3119, 2652 |
Rint | 0.033 |
(sin θ/λ)max (Å−1) | 0.768 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.041, 0.097, 1.04 |
No. of reflections | 3119 |
No. of parameters | 205 |
No. of restraints | 1 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.32, −0.27 |
Selected bond lengths (Å) topO1—C7 | 1.322 (2) | N2—C6 | 1.468 (2) |
O2—C7 | 1.214 (2) | N2—C1 | 1.480 (2) |
O3—C11 | 1.323 (2) | N3—C3 | 1.476 (2) |
O4—C11 | 1.213 (2) | N3—C2 | 1.483 (2) |
N1—C4 | 1.464 (2) | N3—C5 | 1.494 (2) |
N1—C5 | 1.466 (2) | N4—C3 | 1.476 (2) |
N1—C1 | 1.483 (2) | N4—C6 | 1.481 (2) |
N2—C2 | 1.464 (2) | N4—C4 | 1.485 (2) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1O···N3 | 0.88 (3) | 1.80 (3) | 2.6808 (19) | 175 (3) |
O3—H3O···N4 | 0.93 (3) | 1.72 (3) | 2.6518 (19) | 177 (3) |
C1—H1A···O4i | 0.99 | 2.54 | 3.435 (2) | 150 |
C1—H1B···O2ii | 0.99 | 2.40 | 3.317 (2) | 153 |
C2—H2A···O2ii | 0.99 | 2.56 | 3.436 (2) | 147 |
C3—H3A···N2iii | 0.99 | 2.58 | 3.487 (2) | 152 |
C3—H3B···N1iv | 0.99 | 2.48 | 3.355 (2) | 147 |
C4—H4A···O4i | 0.99 | 2.48 | 3.388 (2) | 152 |
Symmetry codes: (i) x−1/2, −y+1/2, z; (ii) −x+1/2, y−1/2, z; (iii) −x+1/2, y+1/2, z; (iv) x+1/2, −y+1/2, z. |
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Hexamethylenetetramine (C6H12N4, also known as hexamine and urotropine, and abbreviated as HMT) forms one-, two- and three-dimensional structures with dicarboxylic acids and phenols (Gaillard et al., 1996, 1998; Hostettler et al., 1999; Lough et al., 2000; Coupar Ferguson et al., 1997; Coupar Glidewell & Ferguson, 1997; Mak, 1965; Jordan & Mak, 1970). These self-assembled co-crystalline molecular adducts of HMT with dicarboxylic acids are usually interconnected by hydrogen bonds, with the N atoms of HMT acting as acceptors and the carboxyl H atoms as donors. Similarly, HMT with alkanedioic acids [HOOC-(CH2)n-COOH] forms 1:1 crystalline adducts with rich phase diagrams. Trimesic acid (benzene-1,3,5-tricarboxylic acid), with its three carboxylic acid groups, has been extensively used in the creation of highly ordered co-crystalline solids. Shan et al. (2003) used a range of bases, including HMT, with cyclohexane-1,3-cis,5-cis-tricarboxylic acid to form supramolecular motifs. In the present study, we used racemic 1,2-trans-cyclohexanedicarboxylic acid, CDA, with the possibility of double deprotonation, to bind with HMT to form similar co-crystalline solids. Pale-yellow rectangular prisms of the title adduct, (I), resulted by mixing hot ethanol solutions of HMT and CDA (in 1:1 molar ratio) and evaporating the mixture at room temperature. Unlike in other systems involving HMT and dicarboxylic acids, we have found only one stoichiometric co-crystal of HMT with CDA. In this report, we present the crystal structure of the adduct, (I). \sch
The asymmetric unit of the co-crystal of CDA and HMT consists of one HMT molecule in a general position and two CDA molecules lying on a crystallographic twofold axis. The one independent COOH group on each CDA molecule forms a hydrogen bond with an N atom on the HMT molecule, and the twofold axis thus forms a hydrogen-bonded rhombus with formula CDA2HMT2 (Fig. 1). Details of the hydrogen bonds, which are essentially linear, are given in Table 2. Although the crystal is racemic, both CDA molecules in any given hydrogen-bonded rhombus have the same handedness.
There is a mismatch in number between the two strong hydrogen-bond donors on CDA and the total of six acceptors (four N on HMT and two C═O on CDA), so formation of the hydrogen-bonded rhombus precludes any extended hydrogen-bonding network. In the absence of such a network, weaker C—H···O and C—H···N interactions involve the remaining acceptors. These are also detailed in Table 2, which shows that all C—H donors are HMT CH2 groups. The two excess HMT N atoms each accept one C—H···N interaction, and each CDA C═O accepts two C—H···O interactions. These weaker interactions allow the perching of two HMT molecules above and below each rhombus. This results in alternating layers of HMT and CDA molecules each 1/4 translation along the polar c axis, as shown in Fig. 2.
The space group for (I) is uncommon, being reported for approximately 0.1% of the entries in the Cambridge Structural Database (Version?; Allen, 2002). In their analysis of space-group frequencies, Brock & Dunitz (1994) found that twofold axes in this space group are usually occupied, with 18 of 24 structures in their sample having Z' = 1/2.