organic compounds
Benzylammonium heptanoate
aBP Institute and Department of Chemistry, University of Cambridge, Cambridge, England
*Correspondence e-mail: stuart@bpi.cam.ac.uk
The title 1:1 stoichiometric salt, C7H10N+·C7H13O2−, is formed by proton transfer between heptanoic acid and benzylamine. This combination contrasts to the recently published 2:1 acid–amine adduct of cation, anion and neutral acid molecule from the same components [Wood & Clarke (2013). Acta Cryst. E69, o346–o347]. There are N—H⋯O hydrogen bonds of moderate strength in the structure [the most important graph-set motifs are R24(8) and R44(12)], as well as weak C—H⋯O interactions.
Related literature
For spectroscopic studies of acid–amine complexes, see: Kohler et al. (1981); Karlsson et al. (2000); Paivarinta et al. (2000); Smith et al. (2001, 2002). For recent diffraction studies of acid–amine complexes, see: Jefferson et al. (2011); Sun et al. (2011); Wood & Clarke (2012a,b, 2013). For the categorization of hydrogen bonds, see Gilli & Gilli (2009). For graph-set motifs, see Etter et al. (1990).
Experimental
Crystal data
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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. , 1993); 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
https://doi.org/10.1107/S1600536813009574/fb2281sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536813009574/fb2281Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S1600536813009574/fb2281Isup3.cml
Benzylamine and heptanoic acid (purities 99.7% and 99.8% respectively, determined by titration and gas chromatography) were purchased from Sigma Aldrich and used without further purification. A small volume of amine (approximately 1 ml) was placed into a small vial that was itself placed within a larger vial containing a similar volume of the acid, and left in an inert atmosphere. Extensive crystal growth was observed after a few weeks, particularly on a polypropylene surface included in the vial to encourage nucleation.
All the hydrogens were discernible in the difference
Nevertheless, the hydrogens attached to the C atoms were situated in the idealized positions and refined under these constraints: Caryl-Haryl=0.95, Cmethyl-Hmethyl=0.98, Cmethylene-Hmethylene=0.99 Å. Ueq(Haryl)=1.2Uiso(Caryl), Ueq(Hmethylene)=1.2Uiso(Cmethylene), Ueq(Hmethyl)=1.5Uiso(Cmethyl). The positional parameters of the hydrogens attached to N of the benzylammonium cation were freely refined while their Ueq(HN)=1.5Uiso(HN).There exist in the literature a number of examples of complexes formed between alkyl
and These have been identified by a number of experimental methods, such as NMR and IR spectroscopy (e. g. Karlsson et al., 2000; Paivarinta et al. (2000); Smith et al. (2001, 2002)). Unfortunately, the atomic details of the materials and hence the nature of the bonding that can be obtained from single-crystal diffraction has only been determined in a few cases. This is partly due to the challenges in growing crystals large enough to be suitable for single-crystal diffraction. Some crystals of sufficient size have been grown (e. g. Jefferson et al. (2011); Wood & Clarke, 2012a, 2012b). Of the stoichiometic combinations reported to date, the majority have been 1:1 complexes, though some 2:1 and even 3:1 examples have been reported by and NMR spectroscopy, generally when the environment is acid-rich (e. g. Kohler et al., 1981; Sun et al., 2011), and very recently using single-crystal diffraction (Wood & Clarke, 2013).Here we report growth of a suitable crystal for single-crystal X-ray diffraction of a 1:1 complex formed between heptanoic acid and benzylamine (Figs. 1 and 2). This work follows a previous publication (Wood & Clarke, 2013) in which an acid-rich 2:1 complex formed between these two species is described. In the previous work, one acid molecule donates its proton to the amine group and one acid group retains its proton. The hydrogen bonding extends across both the ions and the neutral acid molecule.
As described below, the sample of the present study was grown by vapour phase condensation. Each preparation resulted in a batch of several crystals. The crystal used in this present study was taken from a different region of the same batch of samples as for the 2:1 combination (Wood & Clarke, 2013). We attribute the combination of compositions to the concentration gradients across the vapour streams in the preparation.
In the
of the 1:1 complex (Figs. 1 and 2), each acid anion is involved in N-H···O hydrogen bonds of moderate strength (Gilli & Gilli, 2009) with three surrounding amine molecules (Table 1; Fig. 2), and vice versa each benzylammonium group donates its hydrogen to three different heptanoate molecules. The most important graph set motifs are R24(8) (Etter et al., 1990) - see Fig.3. (In this motif the donated atoms are H1a and H1c and the acceptors are the O2 atoms.) The other important motif is R44(12) with donated hydrogens H1b and H1c and accepting oxygens O1 and O2 (Fig. 3.). Moreover, there are also weak C-H···O interactions present in the structure (Table 1).For spectroscopic studies of acid–amine complexes, see: Kohler et al. (1981); Karlsson et al. (2000); Paivarinta et al. (2000); Smith et al. (2001, 2002). For recent diffraction studies of acid–amine complexes, see: Jefferson et al. (2011); Sun et al. (2011); Wood & Clarke (2012a,b, 2013). For the categorization of hydrogen bonds, see Gilli & Gilli (2009). For graph-set motifs, see Etter et al. (1990).
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. , 1993); 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).Fig. 1. Title molecules with atom labels. The displacement ellipsoids are drawn at the 50% probability level for non-H atoms. H atoms are shown as spheres of arbitrary size. | |
Fig. 2. Hydrogen bonding around the ammonium cation. The symmetry codes: i: 1+x, y, z; ii: 1-x, -y, -z. | |
Fig. 3. A section from the hydrogen bond pattern in the title structure. The symmetry codes: i: 1+x, y, z; ii: 1-x, -y, -z; iii: -x, -y, -z; iv: 2-x, -y, -z; v: -1+x, y, z. |
C7H10N+·C7H13O2− | Z = 2 |
Mr = 237.33 | F(000) = 260 |
Triclinic, P1 | Dx = 1.099 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 5.7379 (2) Å | Cell parameters from 9084 reflections |
b = 7.7338 (3) Å | θ = 1.0–27.5° |
c = 17.1670 (7) Å | µ = 0.07 mm−1 |
α = 97.887 (2)° | T = 180 K |
β = 92.864 (2)° | Needle, colourless |
γ = 107.340 (2)° | 0.46 × 0.07 × 0.05 mm |
V = 716.96 (5) Å3 |
Nonius KappaCCD diffractometer | 3253 independent reflections |
Radiation source: fine-focus sealed tube | 2308 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.043 |
ω and φ scans | θmax = 27.5°, θmin = 3.6° |
Absorption correction: multi-scan (SORTAV; Blessing, 1995) | h = −7→7 |
Tmin = 0.874, Tmax = 0.999 | k = −10→9 |
8415 measured reflections | l = −22→22 |
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)] = 0.054 | Hydrogen site location: difference Fourier map |
wR(F2) = 0.141 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.03 | w = 1/[σ2(Fo2) + (0.0544P)2 + 0.2301P] where P = (Fo2 + 2Fc2)/3 |
3253 reflections | (Δ/σ)max < 0.001 |
164 parameters | Δρmax = 0.32 e Å−3 |
0 restraints | Δρmin = −0.19 e Å−3 |
82 constraints |
C7H10N+·C7H13O2− | γ = 107.340 (2)° |
Mr = 237.33 | V = 716.96 (5) Å3 |
Triclinic, P1 | Z = 2 |
a = 5.7379 (2) Å | Mo Kα radiation |
b = 7.7338 (3) Å | µ = 0.07 mm−1 |
c = 17.1670 (7) Å | T = 180 K |
α = 97.887 (2)° | 0.46 × 0.07 × 0.05 mm |
β = 92.864 (2)° |
Nonius KappaCCD diffractometer | 3253 independent reflections |
Absorption correction: multi-scan (SORTAV; Blessing, 1995) | 2308 reflections with I > 2σ(I) |
Tmin = 0.874, Tmax = 0.999 | Rint = 0.043 |
8415 measured reflections |
R[F2 > 2σ(F2)] = 0.054 | 0 restraints |
wR(F2) = 0.141 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.03 | Δρmax = 0.32 e Å−3 |
3253 reflections | Δρmin = −0.19 e Å−3 |
164 parameters |
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 | 0.7763 (2) | 0.1651 (2) | −0.04200 (8) | 0.0352 (3) | |
H1A | 0.630 (4) | 0.195 (3) | −0.0239 (11) | 0.053* | |
H1B | 0.919 (4) | 0.247 (3) | −0.0072 (12) | 0.053* | |
H1C | 0.752 (4) | 0.033 (3) | −0.0380 (11) | 0.053* | |
C1 | 0.8129 (3) | 0.1865 (2) | −0.12452 (9) | 0.0363 (4) | |
H1D | 0.9629 | 0.1556 | −0.1381 | 0.044* | |
H1E | 0.8402 | 0.3168 | −0.1298 | 0.044* | |
C2 | 0.6010 (3) | 0.06878 (19) | −0.18296 (9) | 0.0300 (3) | |
C3 | 0.6366 (3) | 0.0514 (2) | −0.26288 (10) | 0.0407 (4) | |
H3 | 0.7927 | 0.1102 | −0.2790 | 0.049* | |
C4 | 0.4468 (4) | −0.0507 (3) | −0.31918 (10) | 0.0478 (5) | |
H4 | 0.4734 | −0.0608 | −0.3736 | 0.057* | |
C5 | 0.2196 (3) | −0.1378 (2) | −0.29682 (10) | 0.0448 (4) | |
H5 | 0.0898 | −0.2079 | −0.3356 | 0.054* | |
C6 | 0.1819 (3) | −0.1225 (2) | −0.21798 (10) | 0.0379 (4) | |
H6 | 0.0259 | −0.1830 | −0.2022 | 0.045* | |
C7 | 0.3712 (3) | −0.0191 (2) | −0.16130 (9) | 0.0327 (4) | |
H7 | 0.3430 | −0.0084 | −0.1070 | 0.039* | |
O1 | 0.1339 (2) | 0.37947 (17) | 0.06866 (7) | 0.0499 (4) | |
O2 | 0.35258 (19) | 0.20902 (14) | 0.01788 (6) | 0.0345 (3) | |
C8 | 0.3307 (3) | 0.34204 (19) | 0.06561 (8) | 0.0274 (3) | |
C9 | 0.5477 (3) | 0.4606 (2) | 0.12239 (8) | 0.0297 (3) | |
H9A | 0.5971 | 0.5868 | 0.1097 | 0.036* | |
H9B | 0.6878 | 0.4119 | 0.1154 | 0.036* | |
C10 | 0.4899 (3) | 0.4671 (2) | 0.20864 (8) | 0.0305 (3) | |
H10A | 0.3462 | 0.5117 | 0.2151 | 0.037* | |
H10B | 0.4458 | 0.3413 | 0.2217 | 0.037* | |
C11 | 0.7043 (3) | 0.5911 (2) | 0.26616 (9) | 0.0346 (4) | |
H11A | 0.8487 | 0.5476 | 0.2590 | 0.042* | |
H11B | 0.7467 | 0.7172 | 0.2535 | 0.042* | |
C12 | 0.6502 (4) | 0.5962 (2) | 0.35193 (10) | 0.0472 (5) | |
H12A | 0.6043 | 0.4697 | 0.3643 | 0.057* | |
H12B | 0.5081 | 0.6423 | 0.3594 | 0.057* | |
C13 | 0.8663 (5) | 0.7167 (3) | 0.40931 (11) | 0.0747 (7) | |
H13A | 1.0069 | 0.6686 | 0.4025 | 0.090* | |
H13B | 0.9147 | 0.8422 | 0.3958 | 0.090* | |
C14 | 0.8143 (8) | 0.7273 (5) | 0.49474 (15) | 0.1389 (17) | |
H14A | 0.9597 | 0.8085 | 0.5281 | 0.208* | |
H14B | 0.7732 | 0.6044 | 0.5094 | 0.208* | |
H14C | 0.6761 | 0.7758 | 0.5023 | 0.208* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.0267 (7) | 0.0391 (8) | 0.0357 (7) | 0.0102 (6) | −0.0036 (6) | −0.0059 (6) |
C1 | 0.0289 (8) | 0.0376 (8) | 0.0371 (8) | 0.0054 (7) | 0.0018 (7) | −0.0003 (7) |
C2 | 0.0310 (8) | 0.0260 (7) | 0.0320 (8) | 0.0096 (6) | 0.0007 (6) | −0.0001 (6) |
C3 | 0.0426 (9) | 0.0408 (9) | 0.0362 (9) | 0.0095 (8) | 0.0054 (7) | 0.0040 (7) |
C4 | 0.0623 (12) | 0.0500 (10) | 0.0280 (8) | 0.0155 (9) | −0.0009 (8) | 0.0016 (7) |
C5 | 0.0487 (10) | 0.0405 (9) | 0.0379 (9) | 0.0101 (8) | −0.0157 (8) | −0.0032 (7) |
C6 | 0.0330 (8) | 0.0344 (8) | 0.0428 (9) | 0.0075 (7) | −0.0044 (7) | 0.0033 (7) |
C7 | 0.0307 (8) | 0.0337 (8) | 0.0314 (8) | 0.0087 (6) | −0.0008 (6) | 0.0014 (6) |
O1 | 0.0302 (6) | 0.0555 (8) | 0.0574 (8) | 0.0210 (6) | −0.0126 (5) | −0.0247 (6) |
O2 | 0.0326 (6) | 0.0328 (6) | 0.0359 (6) | 0.0119 (5) | 0.0001 (5) | −0.0052 (5) |
C8 | 0.0275 (7) | 0.0272 (7) | 0.0264 (7) | 0.0079 (6) | 0.0011 (6) | 0.0022 (6) |
C9 | 0.0250 (7) | 0.0309 (8) | 0.0305 (8) | 0.0066 (6) | 0.0003 (6) | 0.0012 (6) |
C10 | 0.0293 (7) | 0.0282 (7) | 0.0309 (8) | 0.0060 (6) | −0.0010 (6) | 0.0020 (6) |
C11 | 0.0363 (8) | 0.0321 (8) | 0.0306 (8) | 0.0059 (7) | −0.0044 (7) | 0.0015 (6) |
C12 | 0.0616 (11) | 0.0419 (10) | 0.0307 (9) | 0.0070 (9) | −0.0012 (8) | 0.0036 (7) |
C13 | 0.0991 (19) | 0.0672 (14) | 0.0341 (10) | −0.0026 (13) | −0.0178 (11) | 0.0004 (10) |
C14 | 0.196 (4) | 0.128 (3) | 0.0330 (13) | −0.031 (3) | −0.0145 (17) | −0.0003 (15) |
N1—C1 | 1.467 (2) | C8—C9 | 1.5148 (19) |
N1—H1A | 0.99 (2) | C9—C10 | 1.531 (2) |
N1—H1B | 0.98 (2) | C9—H9A | 0.9900 |
N1—H1C | 1.00 (2) | C9—H9B | 0.9900 |
C1—C2 | 1.510 (2) | C10—C11 | 1.524 (2) |
C1—H1D | 0.9900 | C10—H10A | 0.9900 |
C1—H1E | 0.9900 | C10—H10B | 0.9900 |
C2—C7 | 1.386 (2) | C11—C12 | 1.518 (2) |
C2—C3 | 1.391 (2) | C11—H11A | 0.9900 |
C3—C4 | 1.384 (2) | C11—H11B | 0.9900 |
C3—H3 | 0.9500 | C12—C13 | 1.521 (3) |
C4—C5 | 1.378 (3) | C12—H12A | 0.9900 |
C4—H4 | 0.9500 | C12—H12B | 0.9900 |
C5—C6 | 1.376 (2) | C13—C14 | 1.507 (3) |
C5—H5 | 0.9500 | C13—H13A | 0.9900 |
C6—C7 | 1.389 (2) | C13—H13B | 0.9900 |
C6—H6 | 0.9500 | C14—H14A | 0.9800 |
C7—H7 | 0.9500 | C14—H14B | 0.9800 |
O1—C8 | 1.2486 (17) | C14—H14C | 0.9800 |
O2—C8 | 1.2653 (17) | ||
C1—N1—H1A | 113.5 (11) | C10—C9—H9A | 109.1 |
C1—N1—H1B | 109.7 (11) | C8—C9—H9B | 109.1 |
H1A—N1—H1B | 107.3 (15) | C10—C9—H9B | 109.1 |
C1—N1—H1C | 107.3 (11) | H9A—C9—H9B | 107.9 |
H1A—N1—H1C | 107.5 (16) | C11—C10—C9 | 112.75 (12) |
H1B—N1—H1C | 111.6 (16) | C11—C10—H10A | 109.0 |
N1—C1—C2 | 114.05 (13) | C9—C10—H10A | 109.0 |
N1—C1—H1D | 108.7 | C11—C10—H10B | 109.0 |
C2—C1—H1D | 108.7 | C9—C10—H10B | 109.0 |
N1—C1—H1E | 108.7 | H10A—C10—H10B | 107.8 |
C2—C1—H1E | 108.7 | C12—C11—C10 | 113.17 (14) |
H1D—C1—H1E | 107.6 | C12—C11—H11A | 108.9 |
C7—C2—C3 | 118.30 (14) | C10—C11—H11A | 108.9 |
C7—C2—C1 | 123.43 (13) | C12—C11—H11B | 108.9 |
C3—C2—C1 | 118.25 (14) | C10—C11—H11B | 108.9 |
C4—C3—C2 | 120.71 (16) | H11A—C11—H11B | 107.8 |
C4—C3—H3 | 119.6 | C11—C12—C13 | 113.06 (16) |
C2—C3—H3 | 119.6 | C11—C12—H12A | 109.0 |
C5—C4—C3 | 120.39 (16) | C13—C12—H12A | 109.0 |
C5—C4—H4 | 119.8 | C11—C12—H12B | 109.0 |
C3—C4—H4 | 119.8 | C13—C12—H12B | 109.0 |
C6—C5—C4 | 119.57 (15) | H12A—C12—H12B | 107.8 |
C6—C5—H5 | 120.2 | C14—C13—C12 | 113.9 (2) |
C4—C5—H5 | 120.2 | C14—C13—H13A | 108.8 |
C5—C6—C7 | 120.24 (16) | C12—C13—H13A | 108.8 |
C5—C6—H6 | 119.9 | C14—C13—H13B | 108.8 |
C7—C6—H6 | 119.9 | C12—C13—H13B | 108.8 |
C2—C7—C6 | 120.78 (15) | H13A—C13—H13B | 107.7 |
C2—C7—H7 | 119.6 | C13—C14—H14A | 109.5 |
C6—C7—H7 | 119.6 | C13—C14—H14B | 109.5 |
O1—C8—O2 | 122.39 (13) | H14A—C14—H14B | 109.5 |
O1—C8—C9 | 117.80 (12) | C13—C14—H14C | 109.5 |
O2—C8—C9 | 119.80 (12) | H14A—C14—H14C | 109.5 |
C8—C9—C10 | 112.28 (12) | H14B—C14—H14C | 109.5 |
C8—C9—H9A | 109.1 |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···O2 | 0.99 (2) | 1.80 (2) | 2.7802 (17) | 168.7 (19) |
N1—H1B···O1i | 0.98 (2) | 1.73 (2) | 2.6993 (17) | 169 (2) |
N1—H1C···O2ii | 1.00 (2) | 1.87 (2) | 2.8590 (18) | 167 (2) |
C1—H1E···O1iii | 0.99 | 2.40 | 3.280 (2) | 148 |
C7—H7···O2 | 0.95 | 2.52 | 3.3528 (19) | 146 |
Symmetry codes: (i) x+1, y, z; (ii) −x+1, −y, −z; (iii) −x+1, −y+1, −z. |
Experimental details
Crystal data | |
Chemical formula | C7H10N+·C7H13O2− |
Mr | 237.33 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 180 |
a, b, c (Å) | 5.7379 (2), 7.7338 (3), 17.1670 (7) |
α, β, γ (°) | 97.887 (2), 92.864 (2), 107.340 (2) |
V (Å3) | 716.96 (5) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.07 |
Crystal size (mm) | 0.46 × 0.07 × 0.05 |
Data collection | |
Diffractometer | Nonius KappaCCD |
Absorption correction | Multi-scan (SORTAV; Blessing, 1995) |
Tmin, Tmax | 0.874, 0.999 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 8415, 3253, 2308 |
Rint | 0.043 |
(sin θ/λ)max (Å−1) | 0.649 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.054, 0.141, 1.03 |
No. of reflections | 3253 |
No. of parameters | 164 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.32, −0.19 |
Computer programs: COLLECT (Nonius, 1998), SCALEPACK (Otwinowski & Minor 1997), DENZO and SCALEPACK (Otwinowski & Minor, 1997), SIR92 (Altomare et al. , 1993), SHELXL97 (Sheldrick, 2008), Mercury (Macrae et al., 2008).
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···O2 | 0.99 (2) | 1.80 (2) | 2.7802 (17) | 168.7 (19) |
N1—H1B···O1i | 0.98 (2) | 1.73 (2) | 2.6993 (17) | 169 (2) |
N1—H1C···O2ii | 1.00 (2) | 1.87 (2) | 2.8590 (18) | 167 (2) |
C1—H1E···O1iii | 0.99 | 2.40 | 3.280 (2) | 148 |
C7—H7···O2 | 0.95 | 2.52 | 3.3528 (19) | 146 |
Symmetry codes: (i) x+1, y, z; (ii) −x+1, −y, −z; (iii) −x+1, −y+1, −z. |
Acknowledgements
We thank the Department of Chemistry, the BP Institute and the Oppenheimer Trust for financial and technical assistance, and Dr J. E. Davies and Dr A. D. Bond for assistance in collecting and analysing the X-ray data.
References
Altomare, A., Cascarano, G., Giacovazzo, C. & Guagliardi, A. (1993). J. Appl. Cryst. 26, 343–350. CrossRef Web of Science IUCr Journals Google Scholar
Blessing, R. H. (1995). Acta Cryst. A51, 33–38. CrossRef CAS Web of Science IUCr Journals Google Scholar
Etter, M. C., MacDonald, J. C. & Bernstein, J. (1990). Acta Cryst. B46, 256–262. CrossRef CAS Web of Science IUCr Journals Google Scholar
Gilli, G. & Gilli, P. (2009). The Nature of the Hydrogen Bond. Outline of a Comprehensive Hydrogen Bond Theory. International Union of Crystallography. Oxford Science Publications. p. 61. New York, Oxford: Oxford University Press, Inc. Google Scholar
Jefferson, A. E., Sun, C., Bond, A. D. & Clarke, S. M. (2011). Acta Cryst. E67, o655. Web of Science CSD CrossRef IUCr Journals Google Scholar
Karlsson, S., Backlund, S. & Friman, R. (2000). Colloid Polym. Sci. 278, 8–14. Web of Science CrossRef CAS Google Scholar
Kohler, F., Atrops, H., Kalali, H., Liebermann, E., Wilhelm, E., Ratkovics, F. & Salamon, T. (1981). J. Phys. Chem. 85, 2520–2524. CrossRef CAS Web of Science Google Scholar
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. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Nonius (1998). COLLECT. Nonius BV, Delft, The Netherlands. Google Scholar
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. Google Scholar
Paivarinta, J., Karlsson, S., Hotokka, M. & Poso, A. (2000). Chem. Phys. Lett. 327, 420–424. CAS Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Smith, G., Wermuth, U. D., Bott, R. C., Healy, P. C. & White, J. M. (2002). Aust. J. Chem. 55, 349–356. Web of Science CSD CrossRef CAS Google Scholar
Smith, G., Wermuth, U. D., Bott, R. C., White, J. M. & Willis, A. C. (2001). Aust. J. Chem. 54, 165–170. Web of Science CSD CrossRef CAS Google Scholar
Sun, S., Bojdys, M. J., Clarke, S. M., Harper, L. D., Castro, M. A. & Medina, S. (2011). Langmuir, 27, 3626–3637. Web of Science CrossRef CAS PubMed Google Scholar
Wood, M. H. & Clarke, S. M. (2012a). Acta Cryst. E68, o3004. CSD CrossRef IUCr Journals Google Scholar
Wood, M. H. & Clarke, S. M. (2012b). Acta Cryst. E68, o3335. CSD CrossRef IUCr Journals Google Scholar
Wood, M. H. & Clarke, S. M. (2013). Acta Cryst. E69, o346–o347. CSD CrossRef CAS IUCr Journals Google Scholar
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.
There exist in the literature a number of examples of complexes formed between alkyl amines and carboxylic acids. These have been identified by a number of experimental methods, such as NMR and IR spectroscopy (e. g. Karlsson et al., 2000; Paivarinta et al. (2000); Smith et al. (2001, 2002)). Unfortunately, the atomic details of the materials and hence the nature of the bonding that can be obtained from single-crystal diffraction has only been determined in a few cases. This is partly due to the challenges in growing crystals large enough to be suitable for single-crystal diffraction. Some crystals of sufficient size have been grown (e. g. Jefferson et al. (2011); Wood & Clarke, 2012a, 2012b). Of the stoichiometic combinations reported to date, the majority have been 1:1 complexes, though some 2:1 and even 3:1 examples have been reported by calorimetry and NMR spectroscopy, generally when the environment is acid-rich (e. g. Kohler et al., 1981; Sun et al., 2011), and very recently using single-crystal diffraction (Wood & Clarke, 2013).
Here we report growth of a suitable crystal for single-crystal X-ray diffraction of a 1:1 complex formed between heptanoic acid and benzylamine (Figs. 1 and 2). This work follows a previous publication (Wood & Clarke, 2013) in which an acid-rich 2:1 complex formed between these two species is described. In the previous work, one acid molecule donates its proton to the amine group and one acid group retains its proton. The hydrogen bonding extends across both the ions and the neutral acid molecule.
As described below, the sample of the present study was grown by vapour phase condensation. Each preparation resulted in a batch of several crystals. The crystal used in this present study was taken from a different region of the same batch of samples as for the 2:1 combination (Wood & Clarke, 2013). We attribute the combination of compositions to the concentration gradients across the vapour streams in the preparation.
In the crystal structure of the 1:1 complex (Figs. 1 and 2), each acid anion is involved in N-H···O hydrogen bonds of moderate strength (Gilli & Gilli, 2009) with three surrounding amine molecules (Table 1; Fig. 2), and vice versa each benzylammonium group donates its hydrogen to three different heptanoate molecules. The most important graph set motifs are R24(8) (Etter et al., 1990) - see Fig.3. (In this motif the donated atoms are H1a and H1c and the acceptors are the O2 atoms.) The other important motif is R44(12) with donated hydrogens H1b and H1c and accepting oxygens O1 and O2 (Fig. 3.). Moreover, there are also weak C-H···O interactions present in the structure (Table 1).