organic compounds
Benzylammonium heptanoate–heptanoic acid (1/1)
aBP Institute and Department of Chemistry, University of Cambridge, Cambridge CB3 0EZ, England
*Correspondence e-mail: stuart@bpi.cam.ac.uk
The title salt, C7H10N+·C7H13O2−·C7H14O2, is an unusual 2:1 stoichiometric combination of two carboxylic acid molecules and one amine. Although there are crystal structures of a number of 1:1 complexes reported in the literature, 2:1 acid amine complexes are rather uncommon. In this case, a proton is transferred between one acid molecule and the amine to give an acid anion and an ammonium cation whilst the other carboxylic acid remains protonated. The species interact strongly via electrostatic forces and hydrogen bonds. In addition we note that the N atom of the ammonium group makes four close contacts to surrounding O atoms. Three of these are hydrogen bonds with neighbouring acid anions while the fourth does not involve a hydrogen atom but is directed towards the carbonyl O atom of the protonated acid. Each of the acid anion O atoms accepts two hydrogen bonds from adjacent N atoms. There is also evidence of short C—H⋯O contacts. There is disorder (occupancy ratio 0.51:0.49) in the alkyl chain of one of the carboxylic acid molecules.
Related literature
For spectroscopic studies of acid–amine complexes, see: Karlsson 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 (2012a,b).
Experimental
Crystal data
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Refinement
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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., 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/S1600536813003012/mw2101sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536813003012/mw2101Isup2.hkl
Supporting information file. DOI: 10.1107/S1600536813003012/mw2101Isup3.cml
Heptanoic acid and benzylamine, with purities of 99.8% and 99.7% respectively (titration and GC), were obtained from Sigma Aldrich and used without further purification. A small volume (approximately 1 mL) of each material was placed into two small vials and placed inside a larger vial with an inert atmosphere of nitrogen for a number of weeks, during which numerous crystals grew, particularly on a sample of polypropylene included as a nucleating surface, and around the top of the outer vial. Reaction of the amine with atmospheric CO2, was prevented by the inert atmosphere (Sun et al. 2011). The samples were measured at a temperature of 180 K.
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).C7H10N+·C7H13O2−·C7H14O2 | F(000) = 1616 |
Mr = 367.52 | Dx = 1.079 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -C 2yc | Cell parameters from 15490 reflections |
a = 25.5516 (5) Å | θ = 1.0–27.5° |
b = 6.3250 (1) Å | µ = 0.07 mm−1 |
c = 27.9899 (6) Å | T = 180 K |
β = 90.639 (1)° | Block, colourless |
V = 4523.27 (15) Å3 | 0.23 × 0.05 × 0.05 mm |
Z = 8 |
Nonius KappaCCD diffractometer | 2353 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.060 |
Thin slice ω and ϕ scans | θmax = 27.5°, θmin = 1.6° |
Absorption correction: multi-scan (SORTAV; Blessing, 1995) | h = −32→32 |
Tmin = 0.910, Tmax = 1.000 | k = −8→8 |
22723 measured reflections | l = −34→36 |
5085 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)] = 0.068 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.238 | H-atom parameters constrained |
S = 0.98 | w = 1/[σ2(Fo2) + (0.1334P)2] where P = (Fo2 + 2Fc2)/3 |
5085 reflections | (Δ/σ)max < 0.001 |
232 parameters | Δρmax = 0.29 e Å−3 |
10 restraints | Δρmin = −0.20 e Å−3 |
C7H10N+·C7H13O2−·C7H14O2 | V = 4523.27 (15) Å3 |
Mr = 367.52 | Z = 8 |
Monoclinic, C2/c | Mo Kα radiation |
a = 25.5516 (5) Å | µ = 0.07 mm−1 |
b = 6.3250 (1) Å | T = 180 K |
c = 27.9899 (6) Å | 0.23 × 0.05 × 0.05 mm |
β = 90.639 (1)° |
Nonius KappaCCD diffractometer | 5085 independent reflections |
Absorption correction: multi-scan (SORTAV; Blessing, 1995) | 2353 reflections with I > 2σ(I) |
Tmin = 0.910, Tmax = 1.000 | Rint = 0.060 |
22723 measured reflections |
R[F2 > 2σ(F2)] = 0.068 | 10 restraints |
wR(F2) = 0.238 | H-atom parameters constrained |
S = 0.98 | Δρmax = 0.29 e Å−3 |
5085 reflections | Δρmin = −0.20 e Å−3 |
232 parameters |
Experimental. Part of the C7H14O2 molecule is disordered over two sites. In the refinement, the disordered carbon atoms were assigned common isotropic displacement parameters and geometric constraints. |
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. Part of the C7H14O2 molecule is disordered over two sites. In the refinement, the disordered carbon atoms were assigned common isotropic displacement parameters and geometric constraints. The dataset presented is one of a number of separate datasets collected from different crystals. Even so, the crystal diffracted very poorly, a fact reflected in the low percentage of observed structure factors, the use of common isotropic displacement parameters for the disordered parts, and the 'unreasonable' bond lengths. The SORTAV process was found to make no significant difference in this case which can be attributed to the Mo radiation and such a small crystal, the tiny mount and minimal oil, as one would expect. The SORTAV process was run as a check and to ensure that the equivalent reflections have been measured correctly - routine in our laboratory. The low percentage of observed reflections is due to the strenuous efforts which were made to measure everything possible with this poor crystal. The theta limit which was set for the data collection (27.5°) was probably higher than ideal but did ensure that nothing was missed. Again this was due to the very small, very poorly diffracting crystal. |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
N1 | 0.25507 (7) | 0.5059 (3) | 0.03427 (7) | 0.0424 (5) | |
H1A | 0.2774 | 0.6144 | 0.0409 | 0.051* | |
H1B | 0.2501 | 0.4962 | 0.0021 | 0.051* | |
H1C | 0.2689 | 0.3828 | 0.0455 | 0.051* | |
C1 | 0.20393 (9) | 0.5458 (5) | 0.05763 (10) | 0.0527 (7) | |
H1D | 0.1792 | 0.4317 | 0.0487 | 0.063* | |
H1E | 0.1893 | 0.6809 | 0.0456 | 0.063* | |
C2 | 0.20856 (9) | 0.5559 (4) | 0.11088 (9) | 0.0473 (7) | |
C3 | 0.21988 (13) | 0.7431 (5) | 0.13377 (12) | 0.0727 (9) | |
H3A | 0.2256 | 0.8670 | 0.1154 | 0.087* | |
C4 | 0.22312 (17) | 0.7544 (8) | 0.18266 (15) | 0.0993 (13) | |
H4A | 0.2314 | 0.8851 | 0.1977 | 0.119* | |
C5 | 0.21472 (16) | 0.5823 (9) | 0.20932 (14) | 0.0980 (13) | |
H5A | 0.2161 | 0.5924 | 0.2432 | 0.118* | |
C6 | 0.20433 (14) | 0.3944 (8) | 0.18833 (14) | 0.0905 (12) | |
H6A | 0.1992 | 0.2723 | 0.2074 | 0.109* | |
C7 | 0.20111 (11) | 0.3793 (5) | 0.13874 (12) | 0.0645 (8) | |
H7A | 0.1938 | 0.2468 | 0.1241 | 0.077* | |
O1 | 0.33127 (6) | −0.1921 (3) | 0.05299 (7) | 0.0546 (5) | |
O2 | 0.28197 (6) | 0.0932 (3) | 0.05844 (6) | 0.0463 (5) | |
C8 | 0.32360 (9) | −0.0055 (4) | 0.06701 (8) | 0.0418 (6) | |
C9 | 0.36768 (10) | 0.1019 (4) | 0.09405 (10) | 0.0534 (7) | |
H9A | 0.3868 | −0.0068 | 0.1128 | 0.064* | |
H9B | 0.3924 | 0.1609 | 0.0705 | 0.064* | |
C10 | 0.35192 (10) | 0.2769 (5) | 0.12763 (10) | 0.0582 (8) | |
H10A | 0.3301 | 0.2162 | 0.1532 | 0.070* | |
H10B | 0.3302 | 0.3803 | 0.1098 | 0.070* | |
C11 | 0.39793 (11) | 0.3921 (5) | 0.15034 (11) | 0.0633 (8) | |
H11A | 0.4199 | 0.2876 | 0.1676 | 0.076* | |
H11B | 0.4195 | 0.4531 | 0.1246 | 0.076* | |
C12 | 0.38396 (13) | 0.5658 (5) | 0.18440 (12) | 0.0705 (9) | |
H12A | 0.3655 | 0.5034 | 0.2120 | 0.085* | |
H12B | 0.3594 | 0.6640 | 0.1682 | 0.085* | |
C13 | 0.43051 (13) | 0.6901 (6) | 0.20273 (12) | 0.0771 (10) | |
H13A | 0.4547 | 0.5922 | 0.2196 | 0.092* | |
H13B | 0.4494 | 0.7494 | 0.1751 | 0.092* | |
C14 | 0.41686 (16) | 0.8661 (7) | 0.23573 (15) | 0.1033 (13) | |
H14A | 0.4481 | 0.9514 | 0.2424 | 0.155* | |
H14B | 0.4036 | 0.8076 | 0.2657 | 0.155* | |
H14C | 0.3899 | 0.9551 | 0.2208 | 0.155* | |
O3 | 0.41440 (7) | −0.3928 (3) | 0.02418 (8) | 0.0701 (6) | |
H3 | 0.3877 | −0.3358 | 0.0358 | 0.105* | |
O4 | 0.35537 (7) | −0.5688 (3) | −0.01877 (8) | 0.0704 (6) | |
C15 | 0.40002 (10) | −0.5389 (5) | −0.00680 (11) | 0.0555 (7) | |
C16 | 0.44577 (11) | −0.6652 (6) | −0.02485 (12) | 0.0709 (9) | |
H16A | 0.4710 | −0.5666 | −0.0395 | 0.085* | |
H16B | 0.4636 | −0.7324 | 0.0028 | 0.085* | |
C17 | 0.43247 (12) | −0.8326 (6) | −0.06032 (14) | 0.0839 (11) | 0.49 |
H17A | 0.4200 | −0.7641 | −0.0901 | 0.101* | 0.49 |
H17B | 0.4033 | −0.9183 | −0.0478 | 0.101* | 0.49 |
C18 | 0.4783 (3) | −0.9817 (12) | −0.0724 (2) | 0.0717 (14)* | 0.49 |
H18A | 0.4777 | −1.1102 | −0.0522 | 0.086* | 0.49 |
H18B | 0.5124 | −0.9096 | −0.0680 | 0.086* | 0.49 |
C19 | 0.4670 (3) | −1.0438 (12) | −0.1319 (3) | 0.0877 (15)* | 0.49 |
H19A | 0.4450 | −0.9367 | −0.1483 | 0.105* | 0.49 |
H19B | 0.4999 | −1.0645 | −0.1496 | 0.105* | 0.49 |
C20 | 0.4385 (3) | −1.2460 (14) | −0.1242 (3) | 0.0993 (19)* | 0.49 |
H20A | 0.4595 | −1.3307 | −0.1013 | 0.119* | 0.49 |
H20B | 0.4053 | −1.2108 | −0.1082 | 0.119* | 0.49 |
C21 | 0.4256 (5) | −1.3835 (17) | −0.1646 (4) | 0.106 (2)* | 0.49 |
H21A | 0.4101 | −1.5150 | −0.1528 | 0.159* | 0.49 |
H21B | 0.4574 | −1.4159 | −0.1823 | 0.159* | 0.49 |
H21C | 0.4005 | −1.3117 | −0.1857 | 0.159* | 0.49 |
C17' | 0.43247 (12) | −0.8326 (6) | −0.06032 (14) | 0.0839 (11) | 0.51 |
H17C | 0.4058 | −0.7777 | −0.0831 | 0.101* | 0.51 |
H17D | 0.4172 | −0.9554 | −0.0435 | 0.101* | 0.51 |
C18' | 0.4805 (3) | −0.9045 (10) | −0.0879 (3) | 0.0717 (14)* | 0.51 |
H18C | 0.5128 | −0.8886 | −0.0684 | 0.086* | 0.51 |
H18D | 0.4842 | −0.8238 | −0.1179 | 0.086* | 0.51 |
C19' | 0.4673 (3) | −1.1640 (12) | −0.0990 (2) | 0.0877 (15)* | 0.51 |
H19C | 0.4995 | −1.2507 | −0.1003 | 0.105* | 0.51 |
H19D | 0.4429 | −1.2248 | −0.0754 | 0.105* | 0.51 |
C20' | 0.4422 (3) | −1.1380 (14) | −0.1470 (3) | 0.0993 (19)* | 0.51 |
H20C | 0.4650 | −1.0449 | −0.1662 | 0.119* | 0.51 |
H20D | 0.4087 | −1.0625 | −0.1426 | 0.119* | 0.51 |
C21' | 0.4310 (5) | −1.3384 (17) | −0.1765 (4) | 0.106 (2)* | 0.51 |
H21D | 0.4203 | −1.2983 | −0.2090 | 0.159* | 0.51 |
H21E | 0.4028 | −1.4191 | −0.1615 | 0.159* | 0.51 |
H21F | 0.4627 | −1.4255 | −0.1777 | 0.159* | 0.51 |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.0403 (11) | 0.0341 (11) | 0.0527 (12) | 0.0018 (9) | −0.0060 (9) | −0.0029 (10) |
C1 | 0.0403 (14) | 0.0564 (17) | 0.0615 (17) | 0.0019 (12) | 0.0005 (12) | −0.0009 (14) |
C2 | 0.0397 (13) | 0.0473 (16) | 0.0549 (16) | 0.0021 (11) | −0.0005 (12) | 0.0002 (14) |
C3 | 0.088 (2) | 0.058 (2) | 0.072 (2) | −0.0087 (17) | 0.0125 (18) | −0.0083 (18) |
C4 | 0.115 (3) | 0.110 (3) | 0.074 (3) | −0.019 (3) | 0.005 (2) | −0.032 (3) |
C5 | 0.090 (3) | 0.145 (4) | 0.059 (2) | 0.008 (3) | 0.000 (2) | −0.007 (3) |
C6 | 0.083 (2) | 0.113 (3) | 0.077 (3) | 0.031 (2) | 0.017 (2) | 0.043 (2) |
C7 | 0.0605 (18) | 0.0527 (18) | 0.081 (2) | 0.0095 (13) | 0.0092 (16) | 0.0057 (17) |
O1 | 0.0454 (10) | 0.0379 (11) | 0.0804 (13) | 0.0005 (8) | −0.0072 (9) | −0.0089 (10) |
O2 | 0.0420 (10) | 0.0388 (10) | 0.0579 (11) | 0.0010 (7) | −0.0100 (8) | −0.0012 (8) |
C8 | 0.0416 (14) | 0.0351 (14) | 0.0485 (15) | −0.0015 (11) | −0.0029 (11) | 0.0009 (12) |
C9 | 0.0452 (14) | 0.0510 (17) | 0.0637 (17) | 0.0000 (12) | −0.0121 (13) | −0.0049 (14) |
C10 | 0.0517 (16) | 0.0588 (18) | 0.0637 (18) | −0.0013 (13) | −0.0142 (13) | −0.0090 (15) |
C11 | 0.0556 (17) | 0.0654 (19) | 0.0686 (19) | −0.0050 (14) | −0.0186 (14) | −0.0105 (16) |
C12 | 0.071 (2) | 0.071 (2) | 0.069 (2) | 0.0005 (16) | −0.0136 (16) | −0.0146 (17) |
C13 | 0.078 (2) | 0.081 (2) | 0.072 (2) | −0.0093 (18) | −0.0075 (17) | −0.0231 (19) |
C14 | 0.106 (3) | 0.101 (3) | 0.103 (3) | −0.017 (2) | −0.001 (2) | −0.037 (2) |
O3 | 0.0422 (11) | 0.0786 (15) | 0.0893 (15) | −0.0003 (9) | −0.0027 (10) | −0.0185 (12) |
O4 | 0.0377 (11) | 0.0696 (14) | 0.1039 (17) | 0.0009 (9) | −0.0006 (10) | −0.0212 (12) |
C15 | 0.0392 (15) | 0.0550 (18) | 0.0724 (19) | −0.0002 (13) | 0.0030 (14) | 0.0057 (16) |
C16 | 0.0455 (16) | 0.087 (2) | 0.080 (2) | 0.0089 (15) | 0.0068 (15) | 0.0007 (19) |
C17 | 0.0503 (18) | 0.082 (2) | 0.119 (3) | 0.0050 (16) | 0.0091 (18) | −0.026 (2) |
C17' | 0.0503 (18) | 0.082 (2) | 0.119 (3) | 0.0050 (16) | 0.0091 (18) | −0.026 (2) |
N1—C1 | 1.489 (3) | C14—H14B | 0.9800 |
N1—H1A | 0.9100 | C14—H14C | 0.9800 |
N1—H1B | 0.9100 | O3—C15 | 1.317 (3) |
N1—H1C | 0.9100 | O3—H3 | 0.8400 |
C1—C2 | 1.495 (4) | O4—C15 | 1.200 (3) |
C1—H1D | 0.9900 | C15—C16 | 1.508 (4) |
C1—H1E | 0.9900 | C16—C17 | 1.488 (5) |
C2—C3 | 1.375 (4) | C16—H16A | 0.9900 |
C2—C7 | 1.377 (4) | C16—H16B | 0.9900 |
C3—C4 | 1.372 (5) | C17—C18 | 1.544 (8) |
C3—H3A | 0.9500 | C17—H17A | 0.9900 |
C4—C5 | 1.338 (6) | C17—H17B | 0.9900 |
C4—H4A | 0.9500 | C18—C19 | 1.732 (10) |
C5—C6 | 1.351 (6) | C18—H18A | 0.9900 |
C5—H5A | 0.9500 | C18—H18B | 0.9900 |
C6—C7 | 1.393 (5) | C19—C20 | 1.489 (10) |
C6—H6A | 0.9500 | C19—H19A | 0.9900 |
C7—H7A | 0.9500 | C19—H19B | 0.9900 |
O1—C8 | 1.260 (3) | C20—C21 | 1.461 (11) |
O2—C8 | 1.254 (3) | C20—H20A | 0.9900 |
C8—C9 | 1.511 (4) | C20—H20B | 0.9900 |
C9—C10 | 1.510 (4) | C21—H21A | 0.9800 |
C9—H9A | 0.9900 | C21—H21B | 0.9800 |
C9—H9B | 0.9900 | C21—H21C | 0.9800 |
C10—C11 | 1.517 (4) | C18'—C19' | 1.704 (9) |
C10—H10A | 0.9900 | C18'—H18C | 0.9900 |
C10—H10B | 0.9900 | C18'—H18D | 0.9900 |
C11—C12 | 1.500 (4) | C19'—C20' | 1.489 (10) |
C11—H11A | 0.9900 | C19'—H19C | 0.9900 |
C11—H11B | 0.9900 | C19'—H19D | 0.9900 |
C12—C13 | 1.511 (4) | C20'—C21' | 1.538 (11) |
C12—H12A | 0.9900 | C20'—H20C | 0.9900 |
C12—H12B | 0.9900 | C20'—H20D | 0.9900 |
C13—C14 | 1.491 (5) | C21'—H21D | 0.9800 |
C13—H13A | 0.9900 | C21'—H21E | 0.9800 |
C13—H13B | 0.9900 | C21'—H21F | 0.9800 |
C14—H14A | 0.9800 | ||
C1—N1—H1A | 109.5 | H13A—C13—H13B | 107.6 |
C1—N1—H1B | 109.5 | C13—C14—H14A | 109.5 |
H1A—N1—H1B | 109.5 | C13—C14—H14B | 109.5 |
C1—N1—H1C | 109.5 | H14A—C14—H14B | 109.5 |
H1A—N1—H1C | 109.5 | C13—C14—H14C | 109.5 |
H1B—N1—H1C | 109.5 | H14A—C14—H14C | 109.5 |
N1—C1—C2 | 112.6 (2) | H14B—C14—H14C | 109.5 |
N1—C1—H1D | 109.1 | C15—O3—H3 | 109.5 |
C2—C1—H1D | 109.1 | O4—C15—O3 | 123.5 (3) |
N1—C1—H1E | 109.1 | O4—C15—C16 | 124.1 (3) |
C2—C1—H1E | 109.1 | O3—C15—C16 | 112.4 (2) |
H1D—C1—H1E | 107.8 | C17—C16—C15 | 115.4 (3) |
C3—C2—C7 | 117.7 (3) | C17—C16—H16A | 108.4 |
C3—C2—C1 | 121.0 (3) | C15—C16—H16A | 108.4 |
C7—C2—C1 | 121.3 (3) | C17—C16—H16B | 108.4 |
C4—C3—C2 | 121.3 (3) | C15—C16—H16B | 108.4 |
C4—C3—H3A | 119.3 | H16A—C16—H16B | 107.5 |
C2—C3—H3A | 119.3 | C16—C17—C18 | 114.4 (4) |
C5—C4—C3 | 120.4 (4) | C16—C17—H17A | 108.7 |
C5—C4—H4A | 119.8 | C18—C17—H17A | 108.7 |
C3—C4—H4A | 119.8 | C16—C17—H17B | 108.7 |
C4—C5—C6 | 120.3 (4) | C18—C17—H17B | 108.7 |
C4—C5—H5A | 119.8 | H17A—C17—H17B | 107.6 |
C6—C5—H5A | 119.8 | C17—C18—C19 | 103.4 (5) |
C5—C6—C7 | 120.2 (4) | C17—C18—H18A | 111.1 |
C5—C6—H6A | 119.9 | C19—C18—H18A | 111.1 |
C7—C6—H6A | 119.9 | C17—C18—H18B | 111.1 |
C2—C7—C6 | 120.1 (3) | C19—C18—H18B | 111.1 |
C2—C7—H7A | 120.0 | H18A—C18—H18B | 109.1 |
C6—C7—H7A | 120.0 | C20—C19—C18 | 97.6 (6) |
O2—C8—O1 | 122.8 (2) | C20—C19—H19A | 112.3 |
O2—C8—C9 | 119.9 (2) | C18—C19—H19A | 112.3 |
O1—C8—C9 | 117.3 (2) | C20—C19—H19B | 112.3 |
C10—C9—C8 | 116.0 (2) | C18—C19—H19B | 112.3 |
C10—C9—H9A | 108.3 | H19A—C19—H19B | 109.8 |
C8—C9—H9A | 108.3 | C21—C20—C19 | 120.4 (8) |
C10—C9—H9B | 108.3 | C21—C20—H20A | 107.2 |
C8—C9—H9B | 108.3 | C19—C20—H20A | 107.2 |
H9A—C9—H9B | 107.4 | C21—C20—H20B | 107.2 |
C9—C10—C11 | 113.7 (2) | C19—C20—H20B | 107.2 |
C9—C10—H10A | 108.8 | H20A—C20—H20B | 106.9 |
C11—C10—H10A | 108.8 | C19'—C18'—H18C | 111.2 |
C9—C10—H10B | 108.8 | C19'—C18'—H18D | 111.2 |
C11—C10—H10B | 108.8 | H18C—C18'—H18D | 109.1 |
H10A—C10—H10B | 107.7 | C20'—C19'—C18' | 98.1 (6) |
C12—C11—C10 | 115.4 (2) | C20'—C19'—H19C | 112.1 |
C12—C11—H11A | 108.4 | C18'—C19'—H19C | 112.1 |
C10—C11—H11A | 108.4 | C20'—C19'—H19D | 112.1 |
C12—C11—H11B | 108.4 | C18'—C19'—H19D | 112.1 |
C10—C11—H11B | 108.4 | H19C—C19'—H19D | 109.8 |
H11A—C11—H11B | 107.5 | C19'—C20'—C21' | 117.9 (8) |
C11—C12—C13 | 113.9 (3) | C19'—C20'—H20C | 107.8 |
C11—C12—H12A | 108.8 | C21'—C20'—H20C | 107.8 |
C13—C12—H12A | 108.8 | C19'—C20'—H20D | 107.8 |
C11—C12—H12B | 108.8 | C21'—C20'—H20D | 107.8 |
C13—C12—H12B | 108.8 | H20C—C20'—H20D | 107.2 |
H12A—C12—H12B | 107.7 | C20'—C21'—H21D | 109.5 |
C14—C13—C12 | 114.2 (3) | C20'—C21'—H21E | 109.5 |
C14—C13—H13A | 108.7 | H21D—C21'—H21E | 109.5 |
C12—C13—H13A | 108.7 | C20'—C21'—H21F | 109.5 |
C14—C13—H13B | 108.7 | H21D—C21'—H21F | 109.5 |
C12—C13—H13B | 108.7 | H21E—C21'—H21F | 109.5 |
C1—C2—C3—C4 | 178.6 (3) | C8—C9—C10—C11 | −174.7 (2) |
C7—C2—C3—C4 | −0.7 (5) | C9—C10—C11—C12 | −179.4 (2) |
C1—C2—C7—C6 | −178.3 (3) | C10—C11—C12—C13 | −174.6 (3) |
C3—C2—C7—C6 | 1.0 (4) | C11—C12—C13—C14 | 178.7 (3) |
C2—C3—C4—C5 | −0.7 (6) | C16—C17—C18—C19 | −146.8 (4) |
C3—C4—C5—C6 | 1.8 (7) | C17—C18—C19—C20 | −95.3 (6) |
C4—C5—C6—C7 | −1.5 (7) | C18—C19—C20—C21 | −171.6 (8) |
C5—C6—C7—C2 | 0.1 (6) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···O1i | 0.91 | 1.87 | 2.773 (3) | 171 |
N1—H1B···O2ii | 0.91 | 1.96 | 2.823 (3) | 158 |
N1—H1C···O2 | 0.91 | 1.90 | 2.781 (3) | 164 |
O3—H3···O1 | 0.84 | 1.78 | 2.610 (3) | 172 |
C1—H1D···O4iii | 0.99 | 2.60 | 3.542 (4) | 160 |
C3—H3A···O2i | 0.95 | 2.59 | 3.456 (4) | 152 |
Symmetry codes: (i) x, y+1, z; (ii) −x+1/2, −y+1/2, −z; (iii) −x+1/2, −y−1/2, −z. |
Experimental details
Crystal data | |
Chemical formula | C7H10N+·C7H13O2−·C7H14O2 |
Mr | 367.52 |
Crystal system, space group | Monoclinic, C2/c |
Temperature (K) | 180 |
a, b, c (Å) | 25.5516 (5), 6.3250 (1), 27.9899 (6) |
β (°) | 90.639 (1) |
V (Å3) | 4523.27 (15) |
Z | 8 |
Radiation type | Mo Kα |
µ (mm−1) | 0.07 |
Crystal size (mm) | 0.23 × 0.05 × 0.05 |
Data collection | |
Diffractometer | Nonius KappaCCD diffractometer |
Absorption correction | Multi-scan (SORTAV; Blessing, 1995) |
Tmin, Tmax | 0.910, 1.000 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 22723, 5085, 2353 |
Rint | 0.060 |
(sin θ/λ)max (Å−1) | 0.649 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.068, 0.238, 0.98 |
No. of reflections | 5085 |
No. of parameters | 232 |
No. of restraints | 10 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.29, −0.20 |
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···O1i | 0.91 | 1.87 | 2.773 (3) | 171 |
N1—H1B···O2ii | 0.91 | 1.96 | 2.823 (3) | 158 |
N1—H1C···O2 | 0.91 | 1.90 | 2.781 (3) | 164 |
O3—H3···O1 | 0.84 | 1.78 | 2.610 (3) | 172 |
C1—H1D···O4iii | 0.99 | 2.60 | 3.542 (4) | 160 |
C3—H3A···O2i | 0.95 | 2.59 | 3.456 (4) | 152 |
Symmetry codes: (i) x, y+1, z; (ii) −x+1/2, −y+1/2, −z; (iii) −x+1/2, −y−1/2, −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 for collecting and analysing the X-ray data.
References
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Stable complexes formed between simple alkyl carboxylic acids and alkyl amines have been reported e.g. (Karlsson et al., 2000; Wood et al., 2012a; Wood et al., 2012b) most commonly from spectroscopic studies. Interestingly there also exist examples of 2:1 and 3:1 acid amine complexes, usually in an acid-rich environment (Sun et al., 2011; Kohler et al., 1981). No equivalent amine-rich complexes have yet been observed, although (Smith et al., 2001) and (Smith et al., 2002) have reported a diamine complex formed between methylamine and dnsa due to deprotonation of the phenolic group in the acid (Smith et al., 2002).
Such acid:amine complexes are generally considered to derive their stablity from the complete transfer of a proton from the acid to the amine with subsequent cation-anion electrostatic interaction and strong hydrogen-bond formation. In 2:1 or higher stoichiometry complexes, the hydrogen bond is considered to extend over the three (or more) species involved. However, because there are very limited single crystal diffraction data, the exact form of the interactions are not clear.
In this paper the crystal structure of the 2:1 complex formed by two heptanoic acid molecules and benzylamine is reported. This complex results from the donation of a proton from one acid to the base, forming a carboxylate anion and an ammonium cation. This pair of ions, along with an additional protonated acid molecule, forms the structure illustrated in Figure 1.
All these species interact strongly by electrostatic forces and hydrogen bonding. Figure 2 illustrates the non-covalent interactions around one ammonium ion. There are three hydrogen bonds around each ammonium group nitrogen atom (indicated by dotted black lines in the Figure). Unexpectedly, an additional short contact is observed between the carbonyl group of a protonated acid and the nitrogen atom of the ammonium ion with no hydrogen atom. This interaction is also indicated by a black dotted line in Figure 2.
Figure 3 illustrates the four hydrogen bonds around each carboxylate ion. Interestingly there are two hydrogen bonds evident for each oxygen (indicated by dotted black lines in the Figure).
An illustration of the two hydrogen bonds made by the protonated acid molecules is given in Figure 4. The non-protonated oxygen forms a hydrogen bond with an adjacent carboxylate ion. The other carbonyl group appears to interact with the nitrogen of an ammonium ion.
The alkyl chain of the protonated acid group shows a significant degree of conformational disorder. The chain is not all trans but shows gauche conformers.