Gallic acid monohydrate

In the crystal structure of the title compound, 3,4,5-tri­hydroxy­benzoic acid monohydrate, C₇H₆O₅·H₂O, the gallic acid mol­ecule is essentially planar and has two intramolecular hydrogen bonds between hydroxyl groups. The H atoms of the three hydroxyl groups are oriented in the same direction around the ring, and form intra- and intermolecular hydrogen bonds. The crystal structure is stabilized by all available intermolecular hydrogen bonds, including also those involving the water mol­ecule.

Key indicators

• Single-crystal X-ray study
• T = 296 K
• Mean [sigma](C-C) = 0.005 Å
• R factor = 0.049
• wR factor = 0.188
• Data-to-parameter ratio = 15.0

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

---

S1. Comment

Gallic acid, 3,4,5-trihydroxybenzoic acid, is a naturally occurring plant phenol which has antitumor and anti-oxidative activity. It induces apotosis in the human myelogenenous leukemic cell line (Sakaguchi et al., 1999; Satoh & Sakagami, 1997). Therefore the determination of its crystal structure is important for the structural clarification of its biological function. For this reason, we intended to analyse its crystal structure. Recently, this was determined in a monohydrate form by Jiang et al. (2000). We have mow determined its structure as a different monohydrated form, (I).

The molecular structure of (I) is essentially planar as shown in Fig. 1. In the molecule, all the H atoms of the three hydroxyl groups are oriented in the same direction around the ring, forming two intramolecular hydrogen bonds between a pair of hydroxyl groups at positions 3 and 4, and at positions 4 and 5. The hydroxyl groups at positions 3 and 4 are also linked to the water-O atom and to the hydroxyl-O atom of a neighbouring molecule by a bifurcated hydrogen bond. This hydrogen-bonding scheme is different from that reported by Jiant et al. (2000), in which only one intramolecular hydrogen bond is present, and one of the three H atoms of the hydroxyl groups is oriented in the reverse direction to the others. Furthermore, a hydrogen bond is formed between the carboxyl groups in the previous structure, but this interaction is not present in the structure reported here. All of the possible hydrogen bonds are present as either intra- or intermolecular interactions, as shown in Table 2. The two different crystal structures and hydrogen-bonding schemes observed for gallic acid monohydrate may have a role in the biological function of this compound.

S2. Experimental

The crystal was obtained by slow evaporation of an ethanol solution.

S3. Refinement

All H atoms were located from difference Fourier maps and were not refined.

Computing details

Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation & Rigaku Corporation, 1999); cell refinement: MSC/AFC Diffractometer Control Software; data reduction: TEXSAN (Molecular Structure Corporation & Rigaku Corporation, 1999); program(s) used to solve structure: SIR88 (Burla et al., 1989) and DIRDIF94 (Beurskens et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: TEXSAN.

Figures

Fig. 1. ORTEPII (Johnson, 1976) drawing of the title compound with the atomic numbering scheme. Ellipsoids for non-H atoms correspond to 50% probability.

(I)

Crystal data

C7H6O5·H2O	F(000) = 392.0
Mr = 188.13	Dx = 1.636 Mg m^−3
Monoclinic, P2/n	Mo Kα radiation, λ = 0.7107 Å
a = 14.15 (1) Å	Cell parameters from 18 reflections
b = 3.622 (9) Å	θ = 10.0–14.3°
c = 15.028 (10) Å	µ = 0.15 mm^−1
β = 97.52 (7)°	T = 296 K
V = 764 (1) Å^3	Needle, colorless
Z = 4	0.50 × 0.10 × 0.03 mm

Data collection

Rigaku AFC-5R diffractometer	θmax = 27.5°, θmin = 4°
ω–2θ scans	h = 0→18
2109 measured reflections	k = −4→0
1766 independent reflections	l = −19→19
764 reflections with I > 2σ(I)	3 standard reflections every 150 reflections
Rint = 0.040	intensity decay: 0.1%

Refinement

Refinement on F^2	H-atom parameters not refined
R[F^2 > 2σ(F^2)] = 0.049	w = 1/[σ^2(Fo^2) + (0.1P)^2] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.188	(Δ/σ)max < 0.001
S = 0.91	Δρmax = 0.31 e Å^−3
1766 reflections	Δρmin = −0.31 e Å^−3
118 parameters

Special details

Refinement. Refinement using reflections with F² > -10.0 σ(F²). The weighted R-factor (wR) and goodness of fit (S) are based on F². R-factor (gt) are based on F. The threshold expression of F² > 2.0 σ(F²) is used only for calculating R-factor (gt).

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.3779 (2)	0.2043 (9)	0.7302 (2)	0.0449 (8)
O2	0.4899 (2)	0.4049 (9)	0.6523 (2)	0.0447 (9)
O3	0.1018 (2)	−0.1394 (8)	0.5049 (2)	0.0338 (7)
O4	0.1550 (2)	0.0075 (8)	0.3430 (2)	0.0334 (7)
O5	0.3351 (2)	0.2679 (8)	0.3286 (2)	0.0336 (7)
O6	0.5102 (2)	0.4879 (8)	0.1313 (2)	0.0370 (7)
C1	0.3455 (2)	0.175 (1)	0.5732 (2)	0.0243 (8)
C2	0.2535 (2)	0.044 (1)	0.5784 (2)	0.0253 (8)
C3	0.1931 (2)	−0.0162 (10)	0.5004 (2)	0.0230 (8)
C4	0.2207 (2)	0.0606 (10)	0.4172 (2)	0.0228 (8)
C5	0.3126 (2)	0.191 (1)	0.4124 (2)	0.0248 (8)
C6	0.3740 (2)	0.243 (1)	0.4905 (2)	0.0264 (8)
C7	0.4124 (3)	0.272 (1)	0.6544 (2)	0.0280 (9)
H1	0.4126	0.2858	0.7748	0.0464*
H2	0.2292	−0.0105	0.6347	0.0464*
H3	0.0777	−0.2436	0.4565	0.0464*
H4	0.1808	0.0710	0.2901	0.0464*
H5	0.3893	0.3730	0.3331	0.0473*
H6	0.4346	0.3306	0.4847	0.0464*
H7	0.4673	0.3675	0.1493	0.0556*
H8	0.5347	0.3636	0.0958	0.0556*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.043 (2)	0.070 (2)	0.021 (1)	−0.018 (2)	0.000 (1)	−0.006 (2)
O2	0.028 (1)	0.069 (2)	0.036 (2)	−0.022 (2)	0.000 (1)	0.002 (2)
O3	0.022 (1)	0.048 (2)	0.031 (1)	−0.012 (1)	0.002 (1)	0.000 (1)
O4	0.026 (1)	0.052 (2)	0.022 (1)	−0.010 (1)	0.0018 (10)	0.003 (1)
O5	0.028 (1)	0.050 (2)	0.024 (1)	−0.008 (1)	0.005 (1)	−0.002 (1)
O6	0.032 (1)	0.052 (2)	0.027 (1)	0.000 (1)	0.004 (1)	−0.009 (1)
C1	0.025 (2)	0.025 (2)	0.022 (2)	−0.002 (2)	0.002 (1)	−0.001 (2)
C2	0.026 (2)	0.025 (2)	0.026 (2)	−0.001 (2)	0.008 (1)	0.002 (2)
C3	0.020 (2)	0.023 (2)	0.027 (2)	−0.004 (2)	0.003 (1)	0.001 (2)
C4	0.022 (2)	0.023 (2)	0.022 (2)	−0.003 (2)	−0.001 (1)	0.000 (2)
C5	0.025 (2)	0.026 (2)	0.025 (2)	−0.001 (2)	0.007 (1)	0.001 (2)
C6	0.017 (2)	0.032 (2)	0.030 (2)	−0.008 (2)	0.002 (1)	−0.002 (2)
C7	0.027 (2)	0.031 (2)	0.025 (2)	−0.003 (2)	0.001 (1)	−0.001 (2)

Geometric parameters (Å, º)

O1—C7	1.317 (5)	O6—H8	0.812
O1—H1	0.830	C1—C2	1.396 (5)
O2—C7	1.203 (5)	C1—C6	1.380 (5)
O3—C3	1.373 (4)	C1—C7	1.487 (5)
O3—H3	0.850	C2—C3	1.376 (4)
O4—C4	1.370 (4)	C2—H2	0.975
O4—H4	0.945	C3—C4	1.391 (5)
O5—C5	1.372 (4)	C4—C5	1.390 (5)
O5—H5	0.851	C5—C6	1.377 (4)
O6—H7	0.820	C6—H6	0.929
O1···O6^i	2.686 (4)	O3···O6^v	2.769 (4)
O1···O2^ii	3.576 (5)	O3···O3^vi	3.039 (5)
O2···O5^i	2.718 (4)	O3···C3^ii	3.432 (5)
O2···O6^i	3.275 (9)	O4···O5^vii	2.772 (4)
O2···C6^i	3.321 (5)	O4···O6^vii	2.977 (4)
O2···C7^iii	3.325 (5)	O5···C5^iii	3.602 (10)
O2···C5^i	3.410 (5)	O6···O3^viii	2.747 (4)
O2···C1^iii	3.569 (5)	O6···O4^vii	2.977 (4)
O3···O6^iv	2.747 (4)
C7—O1—H1	112.7	C2—C3—C4	121.0 (3)
C3—O3—H3	112.3	O4—C4—C3	117.4 (3)
C4—O4—H4	110.6	O4—C4—C5	123.2 (3)
C5—O5—H5	109.5	C3—C4—C5	119.3 (3)
H7—O6—H8	108.7	O5—C5—C4	116.8 (3)
C2—C1—C6	119.7 (3)	O5—C5—C6	124.0 (3)
C2—C1—C7	122.2 (3)	C4—C5—C6	119.6 (3)
C6—C1—C7	118.0 (3)	C1—C6—C5	121.0 (3)
C1—C2—C3	119.3 (3)	C1—C6—H6	121.8
C1—C2—H2	123.7	C5—C6—H6	117.2
C3—C2—H2	117.0	O1—C7—O2	122.6 (3)
O3—C3—C2	119.8 (3)	O1—C7—C1	113.5 (3)
O3—C3—C4	119.2 (3)	O2—C7—C1	123.8 (3)
O1—C7—C1—C2	2.7 (5)	O5—C5—C4—C3	−178.9 (3)
O1—C7—C1—C6	178.6 (3)	O5—C5—C6—C1	177.2 (3)
O2—C7—C1—C2	−175.3 (4)	C1—C2—C3—C4	−1.9 (6)
O2—C7—C1—C6	0.2 (6)	C1—C6—C5—C4	−1.5 (6)
O3—C3—C2—C1	−179.0 (3)	C2—C1—C6—C5	1.4 (6)
O3—C3—C4—O4	−0.2 (5)	C2—C3—C4—C5	1.8 (6)
O3—C3—C4—C5	179.0 (3)	C3—C2—C1—C6	0.3 (6)
O4—C4—C3—C2	−177.3 (3)	C3—C2—C1—C7	175.7 (4)
O4—C4—C5—O5	0.9 (5)	C3—C4—C5—C6	−0.1 (6)
O4—C4—C5—C6	178.9 (4)	C5—C6—C1—C7	−174.2 (4)

Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) x, y−1, z; (iii) x, y+1, z; (iv) x−1/2, −y, z+1/2; (v) −x+1/2, y−1, −z+1/2; (vi) −x, −y, −z+1; (vii) −x+1/2, y, −z+1/2; (viii) x+1/2, −y, z−1/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O3—H3···O4	0.850	2.328	2.692 (8)	106.3
O4—H4···O5	0.945	2.306	2.752 (8)	108.9
O3—H3···O6^v	0.850	1.949	2.770 (4)	161.6
O4—H4···O5^vii	0.945	1.907	2.767 (8)	150.0
O5—H5···O2^i	0.851	1.878	2.729 (4)	177.7
O6—H7···O4^vii	0.820	2.182	2.977 (4)	163.8
O6—H8···O3^viii	0.812	1.941	2.747 (4)	170.9
O1—H1···O6^i	0.830	1.859	2.686 (4)	174.2

Symmetry codes: (i) −x+1, −y+1, −z+1; (v) −x+1/2, y−1, −z+1/2; (vii) −x+1/2, y, −z+1/2; (viii) x+1/2, −y, z−1/2.