DL-Valinium tri­chloro­acetate at 123 K

In the title compound, C₅H₁₂NO₂⁺·C₂Cl₃O₂⁻, the valine mol­ecule is in a cationic state and the tri­chloro­acetic acid is in the anionic state. In the crystal, the intermolecular N—H...O and O—H...O hydrogen bonds link the mol­ecules to form an infinite two-dimensional network parallel to (001).

Key indicators

• Single-crystal X-ray study
• T = 123 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.033
• wR factor = 0.083
• Data-to-parameter ratio = 19.2

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

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S1. Comment

In our laboratory, we have been elucidating the crystal structures of proton-transfer complexes of the type A·B, where A is a amino acid and B is a carboxylic acid which is believed to have existed in the pre-biotic earth (Miller & Orgel, 1974; Kvenvolden et al., 1971). A brief survey on the Cambridge structural Database Database (Allen & Kennard, 1993) revealed scarcity of precise crystallographic data on amino acid–halogeno acetic acid complexes. We report here, the crystal structure of a complex of DL-valine with trichloroacetic acid, namely, DL-valinium trichloroacetate, (I). Systematic X-ray investigation, on such compounds are expected to throw light on the importance of halogen–halogen interactions on biomolecular aggregation patterns. The crystal structure of a complex of a dipeptide with trichloroacetic acid, L-phenylalanylglycine trichloroaceteate is already reported (Mitra & Subramanian, 1993). The crystal structure of trichloroacetic acid still remains unknown.

In (I), the valine molecule is in a cationic state with a positively charged amino group and an uncharged carboxylic acid group. The trichloroacetic acid exists in the anionic state with a negatively charged carboxylate group (Fig. 1). The carboxylate group of valine is planar and the amino nitrogen deviates from this plane by 0.528 (1) Å leading to the twisting of the C—N bond out of the plane of the carboxyl group by 21.9 (1)°. The conformation of the valine molecule determined by the internal rotation angles ψ² [-22.4 (2)], χ¹¹ [-162.9 (1)] and χ¹² [70.9 (1)°] agree well with the values observed for the monoclinic form of DL-valine (Mallikarjunan & Rao, 1969) and for the triclinic form of DL-valine (Dalhus & Görbitz, 1996). However, in DL-valinium maleate (Alagar et al., 2001), χ¹¹ [57.1 (2)°] deviates siginificantly from that observed in the present study. In the crystal, the valine and the trichloroacetic acid molecules are alteratively linked by O—H···O and N—H···O hydrogen bonds to form infinte one-dimensional chains along [110]. The inversion related chains are interlinked by N—H···O hydrogen bonds to form infinite two-dimensional network parallel to (001). In this network, the D and L isomers exist as centrosymmetrically hydrogen-bonded dimers (Table 2).

S2. Experimental

Single crystals of (I) were grown from a saturated aqueous solution containing DL-valine and trichloroacetic acid in stoichiometric ratio.

S3. Refinement

All the H atoms were located from a difference Fourier map and were included in the refinement with isotropic displacement parameters. The range of C—H and N—H bond lengths are 0.96 (3)–0.98 (2) Å and 0.84 (2)–0.90 (2) Å, respectively, and the O—H distance is 0.89 (3) Å.

Computing details

Data collection: SMART-NT (Bruker, 1999); cell refinement: SMART-NT; data reduction: SAINT-NT (Bruker, 1999); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 1999); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The molecular structure of (I) with the atom-numbering scheme and 50% probability displacement ellipsoids.
	Fig. 2. Packing of the molecules of (I) viewed down the a axis.

DL-valinium trichloroacetate

Crystal data

C5H12NO2^+·C2Cl3O2^−	Z = 2
Mr = 280.53	F(000) = 288
Triclinic, P1	Dx = 1.578 Mg m^−3 Dm = 1.60 Mg m^−3 Dm measured by floatation in bromoform and xylene
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 7.2380 (14) Å	Cell parameters from 1024 reflections
b = 8.4150 (17) Å	θ = 2.5–23.0°
c = 10.303 (2) Å	µ = 0.77 mm^−1
α = 106.50 (3)°	T = 123 K
β = 97.50 (3)°	Prismatic, colourless
γ = 95.80 (3)°	0.50 × 0.40 × 0.15 mm
V = 590.2 (2) Å^3

Data collection

Bruker SMART CCD diffractometer	3537 independent reflections
Radiation source: fine-focus sealed tube	3204 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.019
Detector resolution: 8 pixels mm^-1	θmax = 30.7°, θmin = 2.6°
ω scans	h = −9→10
Absorption correction: empirical (using intensity measurements) (SADABS; Bruker, 1998)	k = −11→12
Tmin = 0.68, Tmax = 0.89	l = −14→14
7923 measured 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)] = 0.033	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.083	All H-atom parameters refined
S = 1.04	w = 1/[σ^2(Fo^2) + (0.0346P)^2 + 0.3602P] where P = (Fo^2 + 2Fc^2)/3
3537 reflections	(Δ/σ)max < 0.001
184 parameters	Δρmax = 0.61 e Å^−3
0 restraints	Δρmin = −0.59 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
Cl1	0.30543 (4)	0.87106 (4)	0.82868 (4)	0.03004 (9)
Cl2	0.55245 (5)	1.08232 (6)	0.73112 (7)	0.05368 (15)
Cl3	0.47752 (6)	0.72657 (7)	0.59258 (4)	0.05099 (13)
O1	0.40290 (13)	0.45980 (12)	0.79978 (11)	0.0270 (2)
O2	0.23758 (14)	0.54991 (11)	0.97001 (10)	0.02560 (19)
O3	0.65035 (13)	0.72929 (12)	0.89273 (11)	0.0263 (2)
O4	0.83858 (13)	0.92835 (12)	0.85109 (12)	0.0294 (2)
N	0.03102 (15)	0.24810 (14)	0.91265 (12)	0.0222 (2)
C1	0.26405 (16)	0.44550 (15)	0.86814 (13)	0.0207 (2)
C2	0.13296 (17)	0.28081 (15)	0.80351 (13)	0.0214 (2)
C3	−0.00515 (18)	0.28336 (17)	0.67831 (14)	0.0261 (2)
C4	0.0915 (3)	0.2638 (3)	0.55220 (18)	0.0449 (4)
C5	−0.1044 (2)	0.4382 (2)	0.70797 (17)	0.0352 (3)
C6	0.68459 (17)	0.84578 (14)	0.84195 (13)	0.0202 (2)
C7	0.51198 (17)	0.88333 (16)	0.75411 (14)	0.0241 (2)
H10	0.475 (4)	0.559 (3)	0.835 (3)	0.056 (7)*
H1N	0.116 (3)	0.251 (2)	0.984 (2)	0.035 (5)*
H2N	−0.033 (3)	0.153 (3)	0.885 (2)	0.032 (5)*
H3N	−0.042 (3)	0.328 (2)	0.9425 (19)	0.030 (5)*
H2	0.206 (3)	0.192 (2)	0.7769 (18)	0.023 (4)*
H3	−0.101 (3)	0.181 (2)	0.659 (2)	0.032 (5)*
H41	0.182 (4)	0.360 (3)	0.565 (3)	0.057 (7)*
H42	−0.002 (4)	0.248 (3)	0.470 (3)	0.067 (8)*
H43	0.160 (3)	0.169 (3)	0.535 (2)	0.045 (6)*
H51	−0.195 (3)	0.438 (3)	0.631 (2)	0.051 (6)*
H52	−0.016 (3)	0.537 (3)	0.724 (2)	0.047 (6)*
H53	−0.169 (3)	0.456 (3)	0.788 (2)	0.047 (6)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.02090 (14)	0.02902 (16)	0.0465 (2)	0.00414 (11)	0.01287 (13)	0.01786 (14)
Cl2	0.02408 (17)	0.0534 (3)	0.1099 (4)	0.00881 (16)	0.0161 (2)	0.0630 (3)
Cl3	0.0367 (2)	0.0797 (3)	0.02576 (18)	0.0071 (2)	−0.00067 (14)	0.00196 (19)
O1	0.0187 (4)	0.0204 (4)	0.0395 (5)	−0.0041 (3)	0.0067 (4)	0.0069 (4)
O2	0.0247 (4)	0.0199 (4)	0.0297 (5)	−0.0032 (3)	0.0026 (3)	0.0067 (3)
O3	0.0211 (4)	0.0214 (4)	0.0364 (5)	−0.0032 (3)	−0.0021 (4)	0.0138 (4)
O4	0.0190 (4)	0.0226 (4)	0.0448 (6)	−0.0060 (3)	−0.0015 (4)	0.0132 (4)
N	0.0190 (5)	0.0177 (5)	0.0296 (5)	−0.0031 (4)	0.0012 (4)	0.0100 (4)
C1	0.0159 (5)	0.0169 (5)	0.0294 (6)	−0.0006 (4)	0.0001 (4)	0.0098 (4)
C2	0.0165 (5)	0.0166 (5)	0.0301 (6)	−0.0015 (4)	0.0041 (4)	0.0069 (4)
C3	0.0211 (5)	0.0283 (6)	0.0245 (6)	−0.0049 (5)	0.0019 (4)	0.0049 (5)
C4	0.0385 (9)	0.0610 (12)	0.0300 (8)	−0.0066 (8)	0.0092 (6)	0.0086 (7)
C5	0.0322 (7)	0.0387 (8)	0.0327 (7)	0.0059 (6)	−0.0069 (6)	0.0127 (6)
C6	0.0180 (5)	0.0153 (5)	0.0248 (5)	−0.0006 (4)	0.0012 (4)	0.0043 (4)
C7	0.0173 (5)	0.0262 (6)	0.0324 (6)	0.0014 (4)	0.0050 (4)	0.0146 (5)

Geometric parameters (Å, º)

Cl1—C7	1.7747 (14)	C2—C3	1.5320 (19)
Cl2—C7	1.7580 (14)	C2—H2	0.957 (18)
Cl3—C7	1.7749 (17)	C3—C5	1.525 (2)
O1—C1	1.3150 (16)	C3—C4	1.531 (2)
O1—H10	0.89 (3)	C3—H3	1.00 (2)
O2—C1	1.2136 (17)	C4—H41	0.96 (3)
O3—C6	1.2538 (15)	C4—H42	0.98 (3)
O4—C6	1.2300 (15)	C4—H43	0.97 (2)
N—C2	1.4953 (17)	C5—H51	0.96 (2)
N—H1N	0.89 (2)	C5—H52	0.96 (2)
N—H2N	0.84 (2)	C5—H53	0.98 (2)
N—H3N	0.90 (2)	C6—C7	1.5578 (18)
C1—C2	1.5197 (17)
C1—O1—H10	111.8 (16)	C3—C4—H41	110.6 (15)
C2—N—H1N	108.5 (13)	C3—C4—H42	110.3 (17)
C2—N—H2N	110.6 (14)	H41—C4—H42	110 (2)
H1N—N—H2N	108.0 (18)	C3—C4—H43	112.7 (13)
C2—N—H3N	111.8 (12)	H41—C4—H43	106 (2)
H1N—N—H3N	106.9 (18)	H42—C4—H43	107 (2)
H2N—N—H3N	110.8 (18)	C3—C5—H51	112.5 (14)
O2—C1—O1	125.57 (11)	C3—C5—H52	110.3 (14)
O2—C1—C2	122.27 (11)	H51—C5—H52	104.8 (19)
O1—C1—C2	112.15 (11)	C3—C5—H53	114.8 (13)
N—C2—C1	107.11 (11)	H51—C5—H53	107.3 (19)
N—C2—C3	111.25 (10)	H52—C5—H53	106.5 (19)
C1—C2—C3	112.46 (10)	O4—C6—O3	127.11 (12)
N—C2—H2	107.2 (11)	O4—C6—C7	117.64 (11)
C1—C2—H2	109.2 (11)	O3—C6—C7	115.22 (11)
C3—C2—H2	109.5 (11)	C6—C7—Cl2	112.03 (9)
C5—C3—C4	111.94 (15)	C6—C7—Cl1	111.82 (9)
C5—C3—C2	112.10 (11)	Cl2—C7—Cl1	108.40 (8)
C4—C3—C2	111.28 (13)	C6—C7—Cl3	105.78 (9)
C5—C3—H3	108.9 (11)	Cl2—C7—Cl3	109.62 (8)
C4—C3—H3	107.7 (11)	Cl1—C7—Cl3	109.13 (8)
C2—C3—H3	104.5 (11)
O2—C1—C2—N	−22.42 (16)	C1—C2—C3—C4	76.93 (16)
O1—C1—C2—N	158.59 (10)	O4—C6—C7—Cl2	−20.09 (16)
O2—C1—C2—C3	100.10 (14)	O3—C6—C7—Cl2	161.92 (10)
O1—C1—C2—C3	−78.89 (13)	O4—C6—C7—Cl1	−142.02 (11)
N—C2—C3—C5	70.86 (14)	O3—C6—C7—Cl1	40.00 (14)
C1—C2—C3—C5	−49.30 (15)	O4—C6—C7—Cl3	99.30 (12)
N—C2—C3—C4	−162.91 (13)	O3—C6—C7—Cl3	−78.68 (12)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H10···O3	0.89 (3)	1.72 (3)	2.601 (2)	169 (2)
N—H2N···O4^i	0.84 (2)	1.93 (2)	2.761 (2)	169.6 (19)
N—H1N···O3^ii	0.89 (2)	1.94 (2)	2.804 (2)	163.6 (19)
N—H3N···O2^iii	0.90 (2)	2.00 (2)	2.871 (2)	162.5 (17)

Symmetry codes: (i) x−1, y−1, z; (ii) −x+1, −y+1, −z+2; (iii) −x, −y+1, −z+2.