Crystal structure of iso­butyl­ammonium hydrogen oxalate hemihydrate

In the title hydrated mol­ecular salt, C₄H₁₂N⁺·C₂HO₄⁻·0.5H₂O, the O atom of the water mol­ecule lies on a crystallographic twofold axis. The dihedral angle between the CO₂ and CO₂H planes of the anion is 18.47 (8)°. In the crystal, the anions are connected to each other by strong near-linear O—H⋯O hydrogen bonds. The water mol­ecules are located between the chains of anions and iso­butyl­amine cations; their O atoms participate as donors and acceptors, respectively, in O—H⋯O and N—H⋯O hydrogen bonds, which form channels (dimensions = 4.615 and 3.387 Å) arranged parallel to [010].

1. Related literature

Structure versus properties research is an important area in material engineering, see: Desiraju (2010, 2013). For the crystal structures of oxalic acid salts with aliphatic amines, see: Dziuk et al. (2014a,b); Braga et al. (2012); Ejsmont (2006, 2007)); Ejsmont & Zaleski (2006a,b); MacDonald et al. (2001). For the characteristic structural motifs in ammonium di­carboxyl­ate salts, see: Ali et al. (2012). For motifs of hydrogen bonds containing carboxylate anions, see: Rodríguez-Cuamatzi et al. (2005).

2. Experimental

2.1. Crystal data

• 2C₄H₁₂N⁺·2C₂HO₄⁻·H₂O

• M_r = 344.36

• Monoclinic, C 2/c

• a = 21.2425 (9) Å

• b = 5.6341 (1) Å

• c = 16.5372 (6) Å

• β = 119.141 (5)°

• V = 1728.69 (10) ų

• Z = 4

• Mo Kα radiation

• μ = 0.11 mm⁻¹

• T = 100 K

• 0.30 × 0.17 × 0.16 mm

2.2. Data collection

• Oxford Diffraction Xcalibur diffractometer

• 5536 measured reflections

• 1696 independent reflections

• 1370 reflections with I > 2σ(I)

• R_int = 0.019

2.3. Refinement

• R[F² > 2σ(F²)] = 0.028

• wR(F²) = 0.070

• S = 1.03

• 1696 reflections

• 125 parameters

• H atoms treated by a mixture of independent and constrained refinement

• Δρ_max = 0.22 e Å⁻³

• Δρ_min = −0.20 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1A⋯O8	0.959 (15)	1.963 (15)	2.9111 (13)	169.2 (12)
N1—H1B⋯O9^i	0.877 (15)	2.031 (15)	2.8333 (13)	151.7 (12)
N1—H1B⋯O11^i	0.877 (15)	2.518 (14)	3.1968 (13)	134.8 (11)
N1—H1C⋯O12^ii	0.940 (15)	1.887 (16)	2.8202 (13)	171.4 (13)
O12—H12⋯O8	0.853 (15)	1.893 (15)	2.7423 (10)	173.0 (16)
O10—H10⋯O9^iii	0.988 (17)	1.577 (17)	2.5625 (11)	175.3 (17)
Symmetry codes: (i) -x, -y, -z+1; (ii) x, y-1, z; (iii) x, y+1, z.

Data collection: CrysAlis CCD (Oxford Diffraction, 2008); cell refinement: CrysAlis RED (Oxford Diffraction, 2008); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97.

Supporting information

S1. Comment

Hydrogen bonds are very important in designing new materials. The structure versus properties research is important area in material engineering (Desiraju, 2010, 2013). Carboxylic acid molecules interact in crystals by strong hydrogen bonds, forming different motives e.g. isolated oxalate monoanions, dimers or as in the case of dicarboxylic acids, linear chains (Dziuk et al., 2014a, 2014b; Braga et al., 2012; Ejsmont & Zaleski 2006a, 2006b; Ejsmont, 2006, 2007). The crystal structure of the title salt, (I), consists of isobutylammonium cations, hydrogen oxalate anions and water molecules (Fig. 1). The Cambridge Structural Database (CSD; CONQUEST Version 1.16) has almost 70 structures of oxalic acid salts with aliphatic amines. The geometrical parameters of the isobutylammonium cation (Table 1) are comparable with those found in other crystal structures. The oxalate anions are connected to each other by strong O—H···O hydrogen bonds along the b axis. The isobutylammonium cations form N–H···O type HBs with the anions and water molecules. The O–H···O and N–H···O hydrogen bonds form channels (dimensions = 4.615 Å and 3.387 Å) arranged parallel to [010] direction (Fig. 2 and Table 2).

Related literature

Structure versus properties research is important area in material engineering, see: Desiraju (2010, 2013). For the crystal structures of oxalic acid salts with aliphatic amines, see: Dziuk et al. (2014a,b); Braga et al. (2012); Ejsmont (2006, 2007)); Ejsmont & Zaleski (2006a,b); MacDonald et al. (2001). For the characteristic structural motifs in ammonium dicarboxylate salts, see: Ali et al. (2012). For related literature [on what subject?], see: Rodríguez-Cuamatzi et al. (2005).

S2. Experimental

Colourless prisms of (I) were grown at room temperature by slow evaporation of an aqueous solution containing isobutylamine and oxalic acid in a 1:1 stoichiometric ratio.

S3. Refinement

All H atoms attached to atoms O and N were located in difference electron density maps and were freely refined with isotropic displacement factors [O–H = 0.853 (15) & 0.988 (17) and N–H = 0.877 (15) - 0.959 (15) Å]. The remaining H atoms were positioned geometrically and treated as riding on their parent C atoms, for methine group with distance of 0.98 Å and U_iso (H) = 1.2U_eq(C), for methylene group with distance of 0.97 Å and U_iso (H) = 1.2U_eq(C), for methyl group with distance of 0.96 Å and U_iso (H) = 1.5U_eq(C), no refinement of their parameters.

Computing details

Data collection: CrysAlis CCD (Oxford Diffraction, 2008); cell refinement: CrysAlis RED (Oxford Diffraction, 2008); data reduction: CrysAlis RED (Oxford Diffraction, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

Fig. 1. The molecular structure of (I), showing 50% displacement ellipsoids (arbitrary spheres for the H atoms). Hydrogen bonds are shown as dotted lines.

Fig. 2. The packing diagram of (I), viewed along the b axis, showing the intermolecular hydrogen-bonding scheme (dashed lines).

Isobutylammonium hydrogen oxalate hemihydrate

Crystal data

2C4H12N^+·2C2HO4^−·H2O	F(000) = 744
Mr = 344.36	Dx = 1.323 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 1696 reflections
a = 21.2425 (9) Å	θ = 3.8–26.0°
b = 5.6341 (1) Å	µ = 0.11 mm^−1
c = 16.5372 (6) Å	T = 100 K
β = 119.141 (5)°	Prism, colourless
V = 1728.69 (10) Å^3	0.30 × 0.17 × 0.16 mm
Z = 4

Data collection

Oxford Diffraction Xcalibur diffractometer	1370 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.019
Graphite monochromator	θmax = 26.0°, θmin = 3.8°
Detector resolution: 1024 x 1024 with blocks 2 x 2 pixels mm^-1	h = −26→26
ω scan	k = −5→6
5536 measured reflections	l = −20→20
1696 independent reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.028	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.070	H atoms treated by a mixture of independent and constrained refinement
S = 1.03	w = 1/[σ^2(Fo^2) + (0.0414P)^2 + 0.1361P] where P = (Fo^2 + 2Fc^2)/3
1696 reflections	(Δ/σ)max < 0.001
125 parameters	Δρmax = 0.22 e Å^−3
0 restraints	Δρmin = −0.20 e Å^−3

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
N1	−0.06332 (5)	−0.08724 (18)	0.31560 (7)	0.0152 (2)
H1A	−0.0236 (8)	0.019 (2)	0.3483 (9)	0.031 (4)*
H1B	−0.0747 (8)	−0.146 (2)	0.3559 (10)	0.030 (4)*
H1C	−0.0464 (8)	−0.208 (3)	0.2919 (10)	0.036 (4)*
C2	−0.12455 (6)	0.0404 (2)	0.23817 (8)	0.0165 (3)
H2A	−0.1056	0.1504	0.2102	0.020*
H2B	−0.1500	0.1319	0.2628	0.020*
C3	−0.17707 (6)	−0.1272 (2)	0.16433 (8)	0.0171 (3)
H3A	−0.1503	−0.2241	0.1421	0.021*
C4	−0.23158 (7)	0.0228 (2)	0.08384 (9)	0.0284 (3)
H4A	−0.2066	0.1251	0.0625	0.043*
H4B	−0.2589	0.1170	0.1041	0.043*
H4C	−0.2635	−0.0794	0.0343	0.043*
C5	−0.21430 (7)	−0.2922 (2)	0.20040 (9)	0.0247 (3)
H5A	−0.1788	−0.3842	0.2509	0.037*
H5B	−0.2461	−0.3966	0.1517	0.037*
H5C	−0.2416	−0.2002	0.2214	0.037*
C6	0.07522 (6)	0.27767 (19)	0.47629 (8)	0.0119 (2)
C7	0.08118 (6)	0.52879 (19)	0.51722 (7)	0.0119 (2)
O8	0.05406 (4)	0.25554 (13)	0.39204 (5)	0.0149 (2)
O9	0.09169 (4)	0.11123 (13)	0.53399 (5)	0.0180 (2)
O10	0.08298 (4)	0.69868 (14)	0.46405 (5)	0.0155 (2)
H10	0.0884 (9)	0.855 (3)	0.4940 (12)	0.057 (5)*
O11	0.08261 (4)	0.55763 (14)	0.59056 (5)	0.0169 (2)
O12	0.0000	0.5785 (2)	0.2500	0.0165 (3)
H12	0.0198 (9)	0.486 (3)	0.2967 (10)	0.048 (5)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0170 (5)	0.0171 (5)	0.0115 (5)	−0.0011 (4)	0.0070 (4)	0.0001 (4)
C2	0.0180 (6)	0.0156 (6)	0.0159 (6)	0.0012 (5)	0.0082 (5)	0.0039 (5)
C3	0.0170 (6)	0.0213 (6)	0.0130 (6)	0.0028 (5)	0.0073 (5)	−0.0003 (5)
C4	0.0218 (7)	0.0356 (8)	0.0207 (7)	0.0002 (6)	0.0048 (6)	0.0079 (6)
C5	0.0238 (7)	0.0195 (7)	0.0256 (7)	−0.0044 (5)	0.0080 (6)	0.0005 (5)
C6	0.0120 (6)	0.0123 (6)	0.0127 (6)	0.0000 (4)	0.0072 (5)	0.0004 (4)
C7	0.0098 (6)	0.0131 (6)	0.0117 (5)	0.0001 (4)	0.0043 (4)	0.0010 (4)
O8	0.0216 (4)	0.0129 (4)	0.0110 (4)	0.0002 (3)	0.0087 (4)	−0.0010 (3)
O9	0.0304 (5)	0.0111 (4)	0.0140 (4)	0.0002 (3)	0.0119 (4)	0.0015 (3)
O10	0.0248 (5)	0.0097 (4)	0.0137 (4)	−0.0006 (3)	0.0107 (4)	0.0008 (3)
O11	0.0252 (5)	0.0156 (4)	0.0119 (4)	−0.0009 (3)	0.0106 (4)	−0.0016 (3)
O12	0.0227 (7)	0.0142 (6)	0.0103 (6)	0.000	0.0062 (5)	0.000

Geometric parameters (Å, º)

N1—C2	1.4921 (14)	C4—H4C	0.9600
N1—H1A	0.959 (15)	C5—H5A	0.9600
N1—H1B	0.877 (15)	C5—H5B	0.9600
N1—H1C	0.940 (15)	C5—H5C	0.9600
C2—C3	1.5167 (16)	C6—O8	1.2445 (13)
C2—H2A	0.9700	C6—O9	1.2599 (13)
C2—H2B	0.9700	C6—C7	1.5468 (15)
C3—C5	1.5181 (17)	C7—O11	1.2092 (13)
C3—C4	1.5249 (16)	C7—O10	1.3128 (13)
C3—H3A	0.9800	O10—H10	0.988 (17)
C4—H4A	0.9600	O12—H12	0.853 (15)
C4—H4B	0.9600
C2—N1—H1A	110.0 (8)	C3—C4—H4B	109.5
C2—N1—H1B	112.6 (9)	H4A—C4—H4B	109.5
H1A—N1—H1B	107.4 (12)	C3—C4—H4C	109.5
C2—N1—H1C	110.0 (9)	H4A—C4—H4C	109.5
H1A—N1—H1C	106.2 (12)	H4B—C4—H4C	109.5
H1B—N1—H1C	110.4 (12)	C3—C5—H5A	109.5
N1—C2—C3	112.53 (9)	C3—C5—H5B	109.5
N1—C2—H2A	109.1	H5A—C5—H5B	109.5
C3—C2—H2A	109.1	C3—C5—H5C	109.5
N1—C2—H2B	109.1	H5A—C5—H5C	109.5
C3—C2—H2B	109.1	H5B—C5—H5C	109.5
H2A—C2—H2B	107.8	O8—C6—O9	126.09 (10)
C2—C3—C5	112.62 (9)	O8—C6—C7	119.31 (9)
C2—C3—C4	107.83 (10)	O9—C6—C7	114.58 (9)
C5—C3—C4	111.28 (10)	O11—C7—O10	125.39 (10)
C2—C3—H3A	108.3	O11—C7—C6	121.24 (10)
C5—C3—H3A	108.3	O10—C7—C6	113.37 (9)
C4—C3—H3A	108.3	C7—O10—H10	110.3 (10)
C3—C4—H4A	109.5
N1—C2—C3—C5	63.80 (13)	O9—C6—C7—O11	−18.47 (15)
N1—C2—C3—C4	−173.04 (10)	O8—C6—C7—O10	−18.64 (14)
O8—C6—C7—O11	160.16 (10)	O9—C6—C7—O10	162.72 (9)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···O8	0.959 (15)	1.963 (15)	2.9111 (13)	169.2 (12)
N1—H1B···O9^i	0.877 (15)	2.031 (15)	2.8333 (13)	151.7 (12)
N1—H1B···O11^i	0.877 (15)	2.518 (14)	3.1968 (13)	134.8 (11)
N1—H1C···O12^ii	0.940 (15)	1.887 (16)	2.8202 (13)	171.4 (13)
O12—H12···O8	0.853 (15)	1.893 (15)	2.7423 (10)	173.0 (16)
O10—H10···O9^iii	0.988 (17)	1.577 (17)	2.5625 (11)	175.3 (17)

Symmetry codes: (i) −x, −y, −z+1; (ii) x, y−1, z; (iii) x, y+1, z.