Benzylammonium hepta­noate–hepta­noic acid (1/1)

Wood, M.H.; Clarke, S.M.

doi:10.1107/S1600536813003012

Volume 69
Part 3
Pages o346-o347
March 2013

Received 10 December 2012
Accepted 29 January 2013
Online 6 February 2013

Key indicators
Single-crystal X-ray study
T = 180 K
Mean (C-C) = 0.005 Å
Disorder in main residue
R = 0.068
wR = 0.238
Data-to-parameter ratio = 21.9
Details

Benzylammonium heptanoate-heptanoic acid (1/1)

Mary H. Wood ^a and Stuart M. Clarke ^a ^*

^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-HO 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

C₇H₁₀N⁺·C₇H₁₃O₂^-·C₇H₁₄O₂
M_r = 367.52
Monoclinic, C 2/c
a = 25.5516 (5) Å
b = 6.3250 (1) Å
c = 27.9899 (6) Å
= 90.639 (1)°
V = 4523.27 (15) Å³
Z = 8
Mo K radiation
= 0.07 mm^-1
T = 180 K
0.23 × 0.05 × 0.05 mm

Data collection

Nonius KappaCCD diffractometer
Absorption correction: multi-scan (SORTAV; Blessing, 1995) T_min = 0.910, T_max = 1.000
22723 measured reflections
5085 independent reflections
2353 reflections with I > 2(I)
R_int = 0.060

Refinement

R[F² > 2(F²)] = 0.068
wR(F²) = 0.238
S = 0.98
5085 reflections
232 parameters
10 restraints
H-atom parameters constrained
_max = 0.29 e Å^-3
_min = -0.20 e Å^-3

Table 1
Hydrogen-bond geometry (Å, °)

D-HA	D-H	HA	DA	D-HA
N1-H1AO1ⁱ	0.91	1.87	2.773 (3)	171
N1-H1BO2ⁱⁱ	0.91	1.96	2.823 (3)	158
N1-H1CO2	0.91	1.90	2.781 (3)	164
O3-H3O1	0.84	1.78	2.610 (3)	172
C1-H1DO4ⁱⁱⁱ	0.99	2.60	3.542 (4)	160
C3-H3AO2ⁱ	0.95	2.59	3.456 (4)	152
Symmetry codes: (i) x, y+1, z; (ii) $[-x+{\script{1\over 2}}, -y+{\script{1\over 2}}, -z]$ ; (iii) $[-x+{\script{1\over 2}}, -y-{\script{1\over 2}}, -z]$ .

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

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: MW2101 ).

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

Altomare, A., Cascarano, G., Giacovazzo, C., Guagliardi, A., Burla, M. C., Polidori, G. & Camalli, M. (1994). J. Appl. Cryst. 27, 435.
Blessing, R. H. (1995). Acta Cryst. A51, 33-38.
Jefferson, A. E., Sun, C., Bond, A. D. & Clarke, S. M. (2011). Acta Cryst. E67, o655.
Karlsson, S., Backlund, S. & Friman, R. (2000). Colloid Polym. Sci. 278, 8-14.
Klokkenburg, M., Hilhorst, J. & Erne, B. H. (2007). Vib. Spectrosc. 43, 243-248.
Kohler, F., Atrops, H., Kalali, H., Liebermann, E., Wilhelm, E., Ratkovics, F. & Salamon, T. (1981). J. Phys. Chem. 85, 2520-2524.
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.
Nonius, B. V. (1998). COLLECT. Nonius BV, Delft, The Netherlands.
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.
Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.
Smith, G., Wermuth, U. D., Bott, R. C., Healy, P. C. & White, J. M. (2002). Aust. J. Chem. 55, 349-356.
Smith, G., Wermuth, U. D., Bott, R. C., White, J. M. & Willis, A. C. (2001). Aust. J. Chem. 54, 165-170.
Sun, S., Bojdys, M. J., Clarke, S. M., Harper, L. D., Castro, M. A. & Medina, S. (2011). Langmuir, 27, 3626-3637.
Wood, M. H. & Clarke, S. M. (2012a). Acta Cryst. E68, o3004.
Wood, M. H. & Clarke, S. M. (2012b). Acta Cryst. E68, o3335.

organic compounds