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ISSN: 2056-9890

(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

(Received 26 October 2012; accepted 5 November 2012; online 10 November 2012)

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[Karlsson, S., Backlund, S. & Friman, R. (2000). Colloid Polym. Sci. 278, 8-14.]); Paivarinta et al. (2000[Paivarinta, J., Karlsson, S., Hotokka, M. & Poso, A. (2000). Chem. Phys. Lett. 327, 420-424.]); Kohler et al. (1981[Kohler, F., Atrops, H., Kalali, H., Liebermann, E., Wilhelm, E., Ratkovics, F. & Salamon, T. (1981). J. Phys. Chem. 85, 2520-2524.]); Smith et al. (2001[Smith, G., Wermuth, U. D., Bott, R. C., White, J. M. & Willis, A. C. (2001). Aust. J. Chem. 54, 165-170.], 2002[Smith, G., Wermuth, U. D., Bott, R. C., Healy, P. C. & White, J. M. (2002). Aust. J. Chem. 55, 349-356.]); Klokkenburg et al. (2007[Klokkenburg, M., Hilhorst, J. & Erne, B. H. (2007). Vib. Spectrosc. 43, 243-248.]). For recent diffraction studies of acid–amine complexes, see: Jefferson et al. (2011[Jefferson, A. E., Sun, C., Bond, A. D. & Clarke, S. M. (2011). Acta Cryst. E67, o655.]); Sun et al. (2011[Sun, S., Bojdys, M. J., Clarke, S. M., Harper, L. D., Castro, M. A. & Medina, S. (2011). Langmuir, 27, 3626-3637.]); Wood & Clarke (2012[Wood, M. H. & Clarke, S. M. (2012). Acta Cryst. E68, o3004.]).

[Scheme 1]

Experimental

Crystal data
  • C8H12N+·C6H11O2

  • Mr = 237.33

  • Hexagonal, P 63

  • a = 19.5845 (5) Å

  • c = 6.6307 (2) Å

  • V = 2202.49 (10) Å3

  • Z = 6

  • Mo Kα radiation

  • μ = 0.07 mm−1

  • T = 180 K

  • 0.46 × 0.05 × 0.05 mm

Data collection
  • Nonius KappaCCD diffractometer

  • Absorption correction: multi-scan (SORTAV; Blessing, 1995[Blessing, R. H. (1995). Acta Cryst. A51, 33-38.]) Tmin = 0.740, Tmax = 0.999

  • 11638 measured reflections

  • 1461 independent reflections

  • 1270 reflections with I > 2σ(I)

  • Rint = 0.064

Refinement
  • R[F2 > 2σ(F2)] = 0.040

  • wR(F2) = 0.087

  • S = 1.06

  • 1461 reflections

  • 157 parameters

  • 1 restraint

  • H-atom parameters constrained

  • Δρmax = 0.11 e Å−3

  • Δρmin = −0.14 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA 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-{\script{1\over 2}}].

Data collection: COLLECT (Nonius, 1998[Nonius, B. V. (1998). COLLECT. Nonius BV, Delft, The Netherlands.]); cell refinement: SCALEPACK (Otwinowski & Minor, 1997[Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307-326. New York: Academic Press.]); data reduction: DENZO (Otwinowski & Minor, 1997[Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307-326. New York: Academic Press.]) and SCALEPACK; program(s) used to solve structure: SIR92 (Altomare et al., 1994[Altomare, A., Cascarano, G., Giacovazzo, C., Guagliardi, A., Burla, M. C., Polidori, G. & Camalli, M. (1994). J. Appl. Cryst. 27, 435.]); program(s) used to refine structure: SHELXL97 (Sheldrick 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: Mercury (Macrae et al., 2008[Macrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466-470.]); software used to prepare material for publication: SHELXL97.

Supporting information


Comment top

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.

Related literature top

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 top

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.

Refinement top

The absolute structure 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.

Computing details top

Data collection: COLLECT (Nonius, 1998); cell refinement: 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).

Figures top
[Figure 1] Fig. 1. Perspective view of the asymmetric unit showing one of the three N—H···O hydrogen bonds.
[Figure 2] Fig. 2. Illustration of the molecular packing - top view of a hydrogen bonded chain. Hydrogen bonds are shown by dashed red lines.
[Figure 3] Fig. 3. Illustration of the molecular packing - side view of a hydrogen bonded chain. Hydrogen bonds are shown by dashed red lines and form chains of molecules parallel to the c axis.
(S)-(-)-1-Phenylethanaminium hexanoate top
Crystal data top
C8H12N+·C6H11O2Dx = 1.074 Mg m3
Mr = 237.33Mo Kα radiation, λ = 0.71073 Å
Hexagonal, P63Cell parameters from 7677 reflections
Hall symbol: P 6cθ = 1.0–25.4°
a = 19.5845 (5) ŵ = 0.07 mm1
c = 6.6307 (2) ÅT = 180 K
V = 2202.49 (10) Å3Needle, colourless
Z = 60.46 × 0.05 × 0.05 mm
F(000) = 780
Data collection top
Nonius KappaCCD
diffractometer
1270 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.064
Thin slice ω and ϕ scansθmax = 25.4°, θmin = 3.6°
Absorption correction: multi-scan
(SORTAV; Blessing, 1995)
h = 2322
Tmin = 0.740, Tmax = 0.999k = 2223
11638 measured reflectionsl = 77
1461 independent reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.040Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.087H-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 parametersΔρmax = 0.11 e Å3
1 restraintΔρmin = 0.14 e Å3
Crystal data top
C8H12N+·C6H11O2Z = 6
Mr = 237.33Mo Kα radiation
Hexagonal, P63µ = 0.07 mm1
a = 19.5845 (5) ÅT = 180 K
c = 6.6307 (2) Å0.46 × 0.05 × 0.05 mm
V = 2202.49 (10) Å3
Data collection top
Nonius KappaCCD
diffractometer
1461 independent reflections
Absorption correction: multi-scan
(SORTAV; Blessing, 1995)
1270 reflections with I > 2σ(I)
Tmin = 0.740, Tmax = 0.999Rint = 0.064
11638 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0401 restraint
wR(F2) = 0.087H-atom parameters constrained
S = 1.06Δρmax = 0.11 e Å3
1461 reflectionsΔρmin = 0.14 e Å3
157 parameters
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N10.51079 (11)0.94274 (11)0.0797 (3)0.0332 (4)
H1A0.54370.94910.02460.050*
H1B0.53940.96180.19490.050*
H1C0.48490.96950.05300.050*
C10.49217 (13)0.81354 (13)0.1884 (4)0.0352 (5)
C20.46986 (15)0.77731 (15)0.3746 (4)0.0442 (6)
H20.42950.77970.44830.053*
C30.50523 (17)0.73764 (15)0.4557 (5)0.0530 (7)
H30.48990.71390.58500.064*
C40.56286 (17)0.73265 (15)0.3483 (5)0.0534 (8)
H40.58710.70510.40270.064*
C50.58501 (16)0.76781 (15)0.1621 (5)0.0497 (7)
H50.62460.76420.08790.060*
C60.55026 (14)0.80857 (15)0.0807 (4)0.0415 (6)
H60.56620.83290.04790.050*
C70.45226 (13)0.85703 (14)0.1056 (4)0.0367 (6)
H70.41210.85220.20630.044*
C80.41036 (17)0.82438 (18)0.0939 (5)0.0580 (8)
H8A0.38590.85490.13870.087*
H8B0.36960.76900.07650.087*
H8C0.44860.82810.19510.087*
O10.57647 (10)0.99218 (11)0.4586 (3)0.0445 (5)
O20.60989 (10)0.96859 (11)0.7585 (3)0.0492 (5)
C90.61695 (13)0.97445 (13)0.5718 (4)0.0326 (5)
C100.67789 (14)0.95875 (14)0.4762 (4)0.0360 (5)
H10A0.65320.90130.45290.043*
H10B0.72110.97360.57450.043*
C110.71404 (14)1.00073 (15)0.2782 (4)0.0396 (6)
H11A0.67140.98740.17920.047*
H11B0.74141.05840.30080.047*
C120.77217 (14)0.97868 (14)0.1911 (4)0.0396 (6)
H12A0.81360.99020.29260.048*
H12B0.74420.92120.16470.048*
C130.81090 (17)1.02175 (16)0.0018 (4)0.0495 (7)
H13A0.84261.07890.02670.059*
H13B0.76951.01380.10000.059*
C140.8639 (2)0.99434 (19)0.0959 (5)0.0714 (10)
H14A0.88511.02210.22370.107*
H14B0.83330.93740.12080.107*
H14C0.90751.00580.00370.107*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0388 (10)0.0438 (11)0.0260 (9)0.0273 (9)0.0000 (9)0.0005 (9)
C10.0343 (12)0.0335 (12)0.0342 (13)0.0143 (10)0.0028 (11)0.0051 (12)
C20.0440 (14)0.0454 (14)0.0401 (15)0.0202 (12)0.0053 (12)0.0048 (12)
C30.0592 (17)0.0431 (15)0.0479 (18)0.0189 (14)0.0035 (15)0.0121 (14)
C40.0577 (18)0.0333 (14)0.070 (2)0.0229 (13)0.0176 (16)0.0024 (15)
C50.0481 (15)0.0459 (15)0.0634 (19)0.0297 (13)0.0045 (15)0.0113 (15)
C60.0441 (14)0.0422 (14)0.0392 (13)0.0223 (12)0.0030 (13)0.0027 (12)
C70.0317 (12)0.0433 (13)0.0362 (14)0.0195 (11)0.0033 (11)0.0028 (11)
C80.0509 (17)0.0625 (18)0.059 (2)0.0272 (14)0.0232 (15)0.0104 (16)
O10.0534 (10)0.0647 (11)0.0333 (10)0.0430 (9)0.0058 (9)0.0097 (9)
O20.0512 (11)0.0703 (13)0.0298 (11)0.0331 (10)0.0079 (9)0.0073 (9)
C90.0327 (12)0.0322 (12)0.0300 (15)0.0142 (10)0.0018 (11)0.0032 (11)
C100.0373 (13)0.0420 (13)0.0321 (13)0.0223 (11)0.0006 (11)0.0004 (11)
C110.0427 (14)0.0453 (14)0.0339 (14)0.0244 (12)0.0017 (11)0.0003 (12)
C120.0361 (13)0.0390 (13)0.0406 (14)0.0164 (11)0.0013 (12)0.0020 (12)
C130.0524 (16)0.0557 (16)0.0407 (14)0.0272 (14)0.0092 (13)0.0006 (14)
C140.084 (2)0.0603 (19)0.072 (2)0.0374 (17)0.0398 (19)0.0078 (17)
Geometric parameters (Å, º) top
N1—C71.496 (3)C8—H8C0.9800
N1—H1A0.9100O1—C91.260 (3)
N1—H1B0.9100O2—C91.244 (3)
N1—H1C0.9100C9—C101.513 (3)
C1—C21.382 (4)C10—C111.522 (4)
C1—C61.387 (3)C10—H10A0.9900
C1—C71.518 (3)C10—H10B0.9900
C2—C31.382 (4)C11—C121.519 (3)
C2—H20.9500C11—H11A0.9900
C3—C41.378 (4)C11—H11B0.9900
C3—H30.9500C12—C131.511 (4)
C4—C51.374 (4)C12—H12A0.9900
C4—H40.9500C12—H12B0.9900
C5—C61.391 (4)C13—C141.520 (4)
C5—H50.9500C13—H13A0.9900
C6—H60.9500C13—H13B0.9900
C7—C81.519 (4)C14—H14A0.9800
C7—H71.0000C14—H14B0.9800
C8—H8A0.9800C14—H14C0.9800
C8—H8B0.9800
C7—N1—H1A109.5H8B—C8—H8C109.5
C7—N1—H1B109.5O2—C9—O1124.2 (2)
H1A—N1—H1B109.5O2—C9—C10117.4 (2)
C7—N1—H1C109.5O1—C9—C10118.4 (2)
H1A—N1—H1C109.5C9—C10—C11116.9 (2)
H1B—N1—H1C109.5C9—C10—H10A108.1
C2—C1—C6118.9 (2)C11—C10—H10A108.1
C2—C1—C7119.5 (2)C9—C10—H10B108.1
C6—C1—C7121.6 (2)C11—C10—H10B108.1
C1—C2—C3121.2 (3)H10A—C10—H10B107.3
C1—C2—H2119.4C12—C11—C10112.7 (2)
C3—C2—H2119.4C12—C11—H11A109.0
C4—C3—C2119.8 (3)C10—C11—H11A109.0
C4—C3—H3120.1C12—C11—H11B109.0
C2—C3—H3120.1C10—C11—H11B109.0
C5—C4—C3119.5 (3)H11A—C11—H11B107.8
C5—C4—H4120.2C13—C12—C11113.7 (2)
C3—C4—H4120.2C13—C12—H12A108.8
C4—C5—C6120.9 (3)C11—C12—H12A108.8
C4—C5—H5119.5C13—C12—H12B108.8
C6—C5—H5119.5C11—C12—H12B108.8
C1—C6—C5119.6 (3)H12A—C12—H12B107.7
C1—C6—H6120.2C12—C13—C14113.0 (2)
C5—C6—H6120.2C12—C13—H13A109.0
N1—C7—C1110.52 (17)C14—C13—H13A109.0
N1—C7—C8108.8 (2)C12—C13—H13B109.0
C1—C7—C8113.6 (2)C14—C13—H13B109.0
N1—C7—H7107.9H13A—C13—H13B107.8
C1—C7—H7107.9C13—C14—H14A109.5
C8—C7—H7107.9C13—C14—H14B109.5
C7—C8—H8A109.5H14A—C14—H14B109.5
C7—C8—H8B109.5C13—C14—H14C109.5
H8A—C8—H8B109.5H14A—C14—H14C109.5
C7—C8—H8C109.5H14B—C14—H14C109.5
H8A—C8—H8C109.5
C6—C1—C2—C31.0 (4)C6—C1—C7—N163.3 (3)
C7—C1—C2—C3179.6 (2)C2—C1—C7—C8120.0 (3)
C1—C2—C3—C41.1 (4)C6—C1—C7—C859.4 (3)
C2—C3—C4—C50.5 (4)O2—C9—C10—C11152.0 (2)
C3—C4—C5—C60.3 (4)O1—C9—C10—C1128.2 (3)
C2—C1—C6—C50.3 (4)C9—C10—C11—C12177.9 (2)
C7—C1—C6—C5179.7 (2)C10—C11—C12—C13178.0 (2)
C4—C5—C6—C10.4 (4)C11—C12—C13—C14175.4 (3)
C2—C1—C7—N1117.3 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1A···O2i0.911.842.753 (3)176
N1—H1B···O10.911.872.768 (3)167
N1—H1C···O1ii0.911.822.714 (2)168
Symmetry codes: (i) x, y, z1; (ii) x+1, y+2, z1/2.

Experimental details

Crystal data
Chemical formulaC8H12N+·C6H11O2
Mr237.33
Crystal system, space groupHexagonal, P63
Temperature (K)180
a, c (Å)19.5845 (5), 6.6307 (2)
V3)2202.49 (10)
Z6
Radiation typeMo Kα
µ (mm1)0.07
Crystal size (mm)0.46 × 0.05 × 0.05
Data collection
DiffractometerNonius KappaCCD
diffractometer
Absorption correctionMulti-scan
(SORTAV; Blessing, 1995)
Tmin, Tmax0.740, 0.999
No. of measured, independent and
observed [I > 2σ(I)] reflections
11638, 1461, 1270
Rint0.064
(sin θ/λ)max1)0.602
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.040, 0.087, 1.06
No. of reflections1461
No. of parameters157
No. of restraints1
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)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).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1A···O2i0.911.842.753 (3)176
N1—H1B···O10.911.872.768 (3)167
N1—H1C···O1ii0.911.822.714 (2)168
Symmetry codes: (i) x, y, z1; (ii) x+1, y+2, z1/2.
 

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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