organic compounds
(S)-(−)-1-Phenylethanaminium hexanoate
aBP Institute and Department of Chemistry, University of Cambridge, Cambridge CB3 0EZ, England
*Correspondence e-mail: stuart@bpi.cam.ac.uk
A binary mixture of (S)-(−)-1-phenylethanamine and hexanoic acid was allowed to react to form the title salt, C8H12N+·C6H11O2−. This crystal contains a 1:1 stoichiometric mixture of the acid- and amine-derived species and displays a chiral structure with N—H⋯O hydrogen-bonded chains propagating along the c-axis direction.
Related literature
For spectroscopic studies of acid–amine complexes, see: Karlsson et al. (2000); Paivarinta et al. (2000); Kohler et al. (1981); Smith et al. (2001, 2002); Klokkenburg et al. (2007). For recent diffraction studies of acid–amine complexes, see: Jefferson et al. (2011); Sun et al. (2011); Wood & Clarke (2012).
Experimental
Crystal data
|
Refinement
|
Data collection: COLLECT (Nonius, 1998); cell SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO (Otwinowski & Minor, 1997) and SCALEPACK; program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick 2008); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL97.
Supporting information
10.1107/S1600536812045746/mw2095sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536812045746/mw2095Isup2.hkl
Supporting information file. DOI: 10.1107/S1600536812045746/mw2095Isup3.cml
Hexanoic acid and s-(-)-methylbenzylamine, with purities of 99.5% and 99.8% respectively as determined by titration and GC, were purchased from Sigma Aldrich and used without further purification. The crystals were grown by pipetting a small volume (approximately 1 ml) of each into small vials and leaving within a larger vial along with a polypropylene nucleation surface under an inert atmosphere (to minimize amine reaction with atmospheric CO2 (Sun et al., 2011)). After several weeks abundant crystal growth on the polypropylene surface was observed and a sample selected for X-ray characterization.
Elemental analysis of the crystalline sample gave values of 70.64%, 5.98%, 9.72% and 13.66% for carbon, nitrogen, hydrogen and oxygen respectively. For a 1:1 acid: amine complex, the expected values are: 70.85%, 5.90%, 9.77% and 13.48%, in excellent agreement.
The experimental sample temperature 180 K represents a compromise of improved thermal factors but avoiding sample fracture.
The
was assigned from the known configuration of the starting material. 1183 Friedel pairs were averaged for the refinement.Hydrogen site location were inferred from neighbouring sites and H-atom parameters were constrained in the refinement.
Data collection: COLLECT (Nonius, 1998); cell
SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO and SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick 2008); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL97 (Sheldrick 2008).C8H12N+·C6H11O2− | Dx = 1.074 Mg m−3 |
Mr = 237.33 | Mo Kα radiation, λ = 0.71073 Å |
Hexagonal, P63 | Cell parameters from 7677 reflections |
Hall symbol: P 6c | θ = 1.0–25.4° |
a = 19.5845 (5) Å | µ = 0.07 mm−1 |
c = 6.6307 (2) Å | T = 180 K |
V = 2202.49 (10) Å3 | Needle, colourless |
Z = 6 | 0.46 × 0.05 × 0.05 mm |
F(000) = 780 |
Nonius KappaCCD diffractometer | 1270 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.064 |
Thin slice ω and ϕ scans | θmax = 25.4°, θmin = 3.6° |
Absorption correction: multi-scan (SORTAV; Blessing, 1995) | h = −23→22 |
Tmin = 0.740, Tmax = 0.999 | k = −22→23 |
11638 measured reflections | l = −7→7 |
1461 independent reflections |
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)] = 0.040 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.087 | H-atom parameters constrained |
S = 1.06 | w = 1/[σ2(Fo2) + (0.0379P)2 + 0.3614P] where P = (Fo2 + 2Fc2)/3 |
1461 reflections | (Δ/σ)max < 0.001 |
157 parameters | Δρmax = 0.11 e Å−3 |
1 restraint | Δρmin = −0.14 e Å−3 |
C8H12N+·C6H11O2− | Z = 6 |
Mr = 237.33 | Mo Kα radiation |
Hexagonal, P63 | µ = 0.07 mm−1 |
a = 19.5845 (5) Å | T = 180 K |
c = 6.6307 (2) Å | 0.46 × 0.05 × 0.05 mm |
V = 2202.49 (10) Å3 |
Nonius KappaCCD diffractometer | 1461 independent reflections |
Absorption correction: multi-scan (SORTAV; Blessing, 1995) | 1270 reflections with I > 2σ(I) |
Tmin = 0.740, Tmax = 0.999 | Rint = 0.064 |
11638 measured reflections |
R[F2 > 2σ(F2)] = 0.040 | 1 restraint |
wR(F2) = 0.087 | H-atom parameters constrained |
S = 1.06 | Δρmax = 0.11 e Å−3 |
1461 reflections | Δρmin = −0.14 e Å−3 |
157 parameters |
Experimental. multi-scan from symmetry-related measurements Sortav (Blessing, 1995) |
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. |
x | y | z | Uiso*/Ueq | ||
N1 | 0.51079 (11) | 0.94274 (11) | 0.0797 (3) | 0.0332 (4) | |
H1A | 0.5437 | 0.9491 | −0.0246 | 0.050* | |
H1B | 0.5394 | 0.9618 | 0.1949 | 0.050* | |
H1C | 0.4849 | 0.9695 | 0.0530 | 0.050* | |
C1 | 0.49217 (13) | 0.81354 (13) | 0.1884 (4) | 0.0352 (5) | |
C2 | 0.46986 (15) | 0.77731 (15) | 0.3746 (4) | 0.0442 (6) | |
H2 | 0.4295 | 0.7797 | 0.4483 | 0.053* | |
C3 | 0.50523 (17) | 0.73764 (15) | 0.4557 (5) | 0.0530 (7) | |
H3 | 0.4899 | 0.7139 | 0.5850 | 0.064* | |
C4 | 0.56286 (17) | 0.73265 (15) | 0.3483 (5) | 0.0534 (8) | |
H4 | 0.5871 | 0.7051 | 0.4027 | 0.064* | |
C5 | 0.58501 (16) | 0.76781 (15) | 0.1621 (5) | 0.0497 (7) | |
H5 | 0.6246 | 0.7642 | 0.0879 | 0.060* | |
C6 | 0.55026 (14) | 0.80857 (15) | 0.0807 (4) | 0.0415 (6) | |
H6 | 0.5662 | 0.8329 | −0.0479 | 0.050* | |
C7 | 0.45226 (13) | 0.85703 (14) | 0.1056 (4) | 0.0367 (6) | |
H7 | 0.4121 | 0.8522 | 0.2063 | 0.044* | |
C8 | 0.41036 (17) | 0.82438 (18) | −0.0939 (5) | 0.0580 (8) | |
H8A | 0.3859 | 0.8549 | −0.1387 | 0.087* | |
H8B | 0.3696 | 0.7690 | −0.0765 | 0.087* | |
H8C | 0.4486 | 0.8281 | −0.1951 | 0.087* | |
O1 | 0.57647 (10) | 0.99218 (11) | 0.4586 (3) | 0.0445 (5) | |
O2 | 0.60989 (10) | 0.96859 (11) | 0.7585 (3) | 0.0492 (5) | |
C9 | 0.61695 (13) | 0.97445 (13) | 0.5718 (4) | 0.0326 (5) | |
C10 | 0.67789 (14) | 0.95875 (14) | 0.4762 (4) | 0.0360 (5) | |
H10A | 0.6532 | 0.9013 | 0.4529 | 0.043* | |
H10B | 0.7211 | 0.9736 | 0.5745 | 0.043* | |
C11 | 0.71404 (14) | 1.00073 (15) | 0.2782 (4) | 0.0396 (6) | |
H11A | 0.6714 | 0.9874 | 0.1792 | 0.047* | |
H11B | 0.7414 | 1.0584 | 0.3008 | 0.047* | |
C12 | 0.77217 (14) | 0.97868 (14) | 0.1911 (4) | 0.0396 (6) | |
H12A | 0.8136 | 0.9902 | 0.2926 | 0.048* | |
H12B | 0.7442 | 0.9212 | 0.1647 | 0.048* | |
C13 | 0.81090 (17) | 1.02175 (16) | −0.0018 (4) | 0.0495 (7) | |
H13A | 0.8426 | 1.0789 | 0.0267 | 0.059* | |
H13B | 0.7695 | 1.0138 | −0.1000 | 0.059* | |
C14 | 0.8639 (2) | 0.99434 (19) | −0.0959 (5) | 0.0714 (10) | |
H14A | 0.8851 | 1.0221 | −0.2237 | 0.107* | |
H14B | 0.8333 | 0.9374 | −0.1208 | 0.107* | |
H14C | 0.9075 | 1.0058 | −0.0037 | 0.107* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.0388 (10) | 0.0438 (11) | 0.0260 (9) | 0.0273 (9) | 0.0000 (9) | −0.0005 (9) |
C1 | 0.0343 (12) | 0.0335 (12) | 0.0342 (13) | 0.0143 (10) | −0.0028 (11) | −0.0051 (12) |
C2 | 0.0440 (14) | 0.0454 (14) | 0.0401 (15) | 0.0202 (12) | 0.0053 (12) | 0.0048 (12) |
C3 | 0.0592 (17) | 0.0431 (15) | 0.0479 (18) | 0.0189 (14) | −0.0035 (15) | 0.0121 (14) |
C4 | 0.0577 (18) | 0.0333 (14) | 0.070 (2) | 0.0229 (13) | −0.0176 (16) | −0.0024 (15) |
C5 | 0.0481 (15) | 0.0459 (15) | 0.0634 (19) | 0.0297 (13) | −0.0045 (15) | −0.0113 (15) |
C6 | 0.0441 (14) | 0.0422 (14) | 0.0392 (13) | 0.0223 (12) | 0.0030 (13) | −0.0027 (12) |
C7 | 0.0317 (12) | 0.0433 (13) | 0.0362 (14) | 0.0195 (11) | 0.0033 (11) | 0.0028 (11) |
C8 | 0.0509 (17) | 0.0625 (18) | 0.059 (2) | 0.0272 (14) | −0.0232 (15) | −0.0104 (16) |
O1 | 0.0534 (10) | 0.0647 (11) | 0.0333 (10) | 0.0430 (9) | −0.0058 (9) | −0.0097 (9) |
O2 | 0.0512 (11) | 0.0703 (13) | 0.0298 (11) | 0.0331 (10) | 0.0079 (9) | 0.0073 (9) |
C9 | 0.0327 (12) | 0.0322 (12) | 0.0300 (15) | 0.0142 (10) | −0.0018 (11) | −0.0032 (11) |
C10 | 0.0373 (13) | 0.0420 (13) | 0.0321 (13) | 0.0223 (11) | −0.0006 (11) | −0.0004 (11) |
C11 | 0.0427 (14) | 0.0453 (14) | 0.0339 (14) | 0.0244 (12) | 0.0017 (11) | 0.0003 (12) |
C12 | 0.0361 (13) | 0.0390 (13) | 0.0406 (14) | 0.0164 (11) | 0.0013 (12) | −0.0020 (12) |
C13 | 0.0524 (16) | 0.0557 (16) | 0.0407 (14) | 0.0272 (14) | 0.0092 (13) | 0.0006 (14) |
C14 | 0.084 (2) | 0.0603 (19) | 0.072 (2) | 0.0374 (17) | 0.0398 (19) | 0.0078 (17) |
N1—C7 | 1.496 (3) | C8—H8C | 0.9800 |
N1—H1A | 0.9100 | O1—C9 | 1.260 (3) |
N1—H1B | 0.9100 | O2—C9 | 1.244 (3) |
N1—H1C | 0.9100 | C9—C10 | 1.513 (3) |
C1—C2 | 1.382 (4) | C10—C11 | 1.522 (4) |
C1—C6 | 1.387 (3) | C10—H10A | 0.9900 |
C1—C7 | 1.518 (3) | C10—H10B | 0.9900 |
C2—C3 | 1.382 (4) | C11—C12 | 1.519 (3) |
C2—H2 | 0.9500 | C11—H11A | 0.9900 |
C3—C4 | 1.378 (4) | C11—H11B | 0.9900 |
C3—H3 | 0.9500 | C12—C13 | 1.511 (4) |
C4—C5 | 1.374 (4) | C12—H12A | 0.9900 |
C4—H4 | 0.9500 | C12—H12B | 0.9900 |
C5—C6 | 1.391 (4) | C13—C14 | 1.520 (4) |
C5—H5 | 0.9500 | C13—H13A | 0.9900 |
C6—H6 | 0.9500 | C13—H13B | 0.9900 |
C7—C8 | 1.519 (4) | C14—H14A | 0.9800 |
C7—H7 | 1.0000 | C14—H14B | 0.9800 |
C8—H8A | 0.9800 | C14—H14C | 0.9800 |
C8—H8B | 0.9800 | ||
C7—N1—H1A | 109.5 | H8B—C8—H8C | 109.5 |
C7—N1—H1B | 109.5 | O2—C9—O1 | 124.2 (2) |
H1A—N1—H1B | 109.5 | O2—C9—C10 | 117.4 (2) |
C7—N1—H1C | 109.5 | O1—C9—C10 | 118.4 (2) |
H1A—N1—H1C | 109.5 | C9—C10—C11 | 116.9 (2) |
H1B—N1—H1C | 109.5 | C9—C10—H10A | 108.1 |
C2—C1—C6 | 118.9 (2) | C11—C10—H10A | 108.1 |
C2—C1—C7 | 119.5 (2) | C9—C10—H10B | 108.1 |
C6—C1—C7 | 121.6 (2) | C11—C10—H10B | 108.1 |
C1—C2—C3 | 121.2 (3) | H10A—C10—H10B | 107.3 |
C1—C2—H2 | 119.4 | C12—C11—C10 | 112.7 (2) |
C3—C2—H2 | 119.4 | C12—C11—H11A | 109.0 |
C4—C3—C2 | 119.8 (3) | C10—C11—H11A | 109.0 |
C4—C3—H3 | 120.1 | C12—C11—H11B | 109.0 |
C2—C3—H3 | 120.1 | C10—C11—H11B | 109.0 |
C5—C4—C3 | 119.5 (3) | H11A—C11—H11B | 107.8 |
C5—C4—H4 | 120.2 | C13—C12—C11 | 113.7 (2) |
C3—C4—H4 | 120.2 | C13—C12—H12A | 108.8 |
C4—C5—C6 | 120.9 (3) | C11—C12—H12A | 108.8 |
C4—C5—H5 | 119.5 | C13—C12—H12B | 108.8 |
C6—C5—H5 | 119.5 | C11—C12—H12B | 108.8 |
C1—C6—C5 | 119.6 (3) | H12A—C12—H12B | 107.7 |
C1—C6—H6 | 120.2 | C12—C13—C14 | 113.0 (2) |
C5—C6—H6 | 120.2 | C12—C13—H13A | 109.0 |
N1—C7—C1 | 110.52 (17) | C14—C13—H13A | 109.0 |
N1—C7—C8 | 108.8 (2) | C12—C13—H13B | 109.0 |
C1—C7—C8 | 113.6 (2) | C14—C13—H13B | 109.0 |
N1—C7—H7 | 107.9 | H13A—C13—H13B | 107.8 |
C1—C7—H7 | 107.9 | C13—C14—H14A | 109.5 |
C8—C7—H7 | 107.9 | C13—C14—H14B | 109.5 |
C7—C8—H8A | 109.5 | H14A—C14—H14B | 109.5 |
C7—C8—H8B | 109.5 | C13—C14—H14C | 109.5 |
H8A—C8—H8B | 109.5 | H14A—C14—H14C | 109.5 |
C7—C8—H8C | 109.5 | H14B—C14—H14C | 109.5 |
H8A—C8—H8C | 109.5 | ||
C6—C1—C2—C3 | 1.0 (4) | C6—C1—C7—N1 | −63.3 (3) |
C7—C1—C2—C3 | −179.6 (2) | C2—C1—C7—C8 | −120.0 (3) |
C1—C2—C3—C4 | −1.1 (4) | C6—C1—C7—C8 | 59.4 (3) |
C2—C3—C4—C5 | 0.5 (4) | O2—C9—C10—C11 | −152.0 (2) |
C3—C4—C5—C6 | 0.3 (4) | O1—C9—C10—C11 | 28.2 (3) |
C2—C1—C6—C5 | −0.3 (4) | C9—C10—C11—C12 | −177.9 (2) |
C7—C1—C6—C5 | −179.7 (2) | C10—C11—C12—C13 | −178.0 (2) |
C4—C5—C6—C1 | −0.4 (4) | C11—C12—C13—C14 | −175.4 (3) |
C2—C1—C7—N1 | 117.3 (2) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···O2i | 0.91 | 1.84 | 2.753 (3) | 176 |
N1—H1B···O1 | 0.91 | 1.87 | 2.768 (3) | 167 |
N1—H1C···O1ii | 0.91 | 1.82 | 2.714 (2) | 168 |
Symmetry codes: (i) x, y, z−1; (ii) −x+1, −y+2, z−1/2. |
Experimental details
Crystal data | |
Chemical formula | C8H12N+·C6H11O2− |
Mr | 237.33 |
Crystal system, space group | Hexagonal, P63 |
Temperature (K) | 180 |
a, c (Å) | 19.5845 (5), 6.6307 (2) |
V (Å3) | 2202.49 (10) |
Z | 6 |
Radiation type | Mo Kα |
µ (mm−1) | 0.07 |
Crystal size (mm) | 0.46 × 0.05 × 0.05 |
Data collection | |
Diffractometer | Nonius KappaCCD diffractometer |
Absorption correction | Multi-scan (SORTAV; Blessing, 1995) |
Tmin, Tmax | 0.740, 0.999 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 11638, 1461, 1270 |
Rint | 0.064 |
(sin θ/λ)max (Å−1) | 0.602 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.040, 0.087, 1.06 |
No. of reflections | 1461 |
No. of parameters | 157 |
No. of restraints | 1 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.11, −0.14 |
Computer programs: COLLECT (Nonius, 1998), DENZO and SCALEPACK (Otwinowski & Minor, 1997), SIR92 (Altomare et al., 1994), SHELXL97 (Sheldrick 2008), Mercury (Macrae et al., 2008).
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···O2i | 0.91 | 1.84 | 2.753 (3) | 176 |
N1—H1B···O1 | 0.91 | 1.87 | 2.768 (3) | 167 |
N1—H1C···O1ii | 0.91 | 1.82 | 2.714 (2) | 168 |
Symmetry codes: (i) x, y, z−1; (ii) −x+1, −y+2, z−1/2. |
Acknowledgements
The authors thank the Department of Chemistry, the BP Institute and the Oppenheimer Trust for financial and technical assistance and Dr J. E. Davies for collecting and analysing the X-ray data.
References
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This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
The existence of stable acid:amine complexes formed from simple acid and amine reagents has been reported in the literature (Klokkenburg et al., 2007; Karlsson et al., 2000). Many examples adopt a 1:1 stoichiometry, although acid-rich complexes are not uncommon, with both 2:1 and 3:1 adducts observed in some cases (Sun et al., 2011; Kohler et al., 1981). Amine-rich complexes are thought to be inherently instable and thus unlikely to form (Paivarinta et al., 2000), although there is a report of a diamine complex formed between methylamine and dnsa (3,5-dinitrosalicyclic acid) due to deprotonation of the phenolic group in the acid (Smith et al., 2001; Smith et al., 2002).
The stability of complexes such as the title compound derives from the reactive exchange of a proton giving cations and anions with a strong electrostatic attraction. These ions subsequently interact via strong hydrogen-bond formation; each ammonium ion in the s-(-)-α-methylbenzylammonium hexanoate example is able to form three hydrogen bonds (shown in Figures 1, 2 and 3). For the acid-rich complexes, the hydrogen bonding is considered to extend over the three (or more) species involved.
This work follows previous findings of the formation of a 1:1 complex of octanoic acid and decylamine using the same method (Jefferson et al., 2011) as well as a 1:1 complex between benzylamine and hexanoic acid (Wood et al., 2012). This work focuses on the use of a chiral amine, s-(-)-α-methylbenzylamine.
Whilst spectroscopic studies identifying such acid:amine complexes are reasonably common, there still only a few examples of single-crystal X-ray data, as reported here. This may be attributed to the difficulty of growing suitable crystals as outlined in the experimental section.