Propyl gallate dihydrate

In the crystal structure of the title compound, C₁₀H₁₂O₅·2H₂O, the mol­ecule of n-propyl 3,4,5-tri­hydroxy­benzoate adopts an essentially planar conformation with a fully extended trans zigzag propyl ester group. The gallate residue has two intramolecular hydrogen bonds between the hydroxyl groups. The crystal structure is stabilized by hydrogen-bonding interactions, utilizing all available sites, and hydro­phobic interactions involving the propyl groups.

Key indicators

• Single-crystal X-ray study
• T = 296 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.046
• wR factor = 0.175
• Data-to-parameter ratio = 15.6

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

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S1. Comment

Gallic acid (3,4,5-trihydroxybenzoic acid) is a naturally occurring plant phenol having antitumor and antioxidative activity. It induces apotosis in human myelogenenous leukemic cell line (Sakaguchi et al., 1999; Satoh & Sakagami, 1997) and it is suggested that the hydroxyl substituent plays an important role in its biological activity. We intend to study the structural characteristics of gallic acid derivatives with amphiphili characteristic by systematically adding alkyl groups. The structure of the n-propyl ester of gallic acid (propyl gallate) as its dihydrate, (I), is reported here. The structure of the closely related gallic acid octyl ester (octyl gallate) with long alkyl group has been determined (Jeffrey & Yeon, 1990).

The molecular structure of (I) is essentially planar with a fully extended trans-zigzag propyl ester group, as shown in Fig. 1. In the molecule, all H atoms of the three hydroxy groups are oriented in the same direction, forming two intramolecular hydrogen bonds between a pair of hydroxyl groups at the 3- and 4-positions, and at the 4- and 5-positions. This intramolecular hydrogen-bonding scheme resembles that found in gallic acid monohydrate (Okabe et al., 2001), but is different from that in its polymorphic form (Jiang et al., 2000). In the latter, one of the three H atoms of the hydroxy groups is oriented in the opposite direction to the others so that only one intramolecular hydrogen bond is present.

In the crystal packing, the methyl groups of the propyl ester regions interact with each other (Fig. 2). The interactions between the methyl groups of the short alkyl groups is different from the interdigitizing interaction with long alkyl chains of octyl gallate (Jeffrey & Yeon, 1990). There are no stacking interactions between the phenyl rings. The benzene ring is shifted slightly towards the ester bond, as reflected by the C1···C1ⁱ separation [symmetry code: (i) 1 - x, 1 - y, -z] of 3.542 (5) Å and the separations O2···C3ⁱ of 3.580 (4) Å and O1···C5ⁱ of 3.492 (3) Å. All of the available hydrogen bonds are present as intra- and intermolecular interactions and are detailed in Table 2.

S2. Experimental

Colorless needles were obtained by slow evaporation from an ethanol solution of the compound.

S3. Refinement

The C-bound H atoms were placed in geometrically calculated positions and included in the final refinement in the riding-model approximation with an overall U_iso value of 1 × U_iso for phenyl H atoms and 1.25 × U_iso for methylene H atoms. The H atoms bound to O atoms were located from a difference map but were included in idealized positions.

Computing details

Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation and Rigaku Corporation, 1999a); cell refinement: MSC/AFC Diffractometer Control Software; data reduction: TEXSAN (Molecular Structure Corporation and Rigaku Corporation, 1999b); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); software used to prepare material for publication: TEXSAN.

Figures

	Fig. 1. ORTEPII (Johnson, 1976) drawing of the title compound showing the atomic numbering scheme. Ellipsoids for non-H atoms correspond to 50% probability ellipsoids.
	Fig. 2. Crystal packing viewed down the c axis indicating the hydrogen bonds (fine lines) and interactions between the propyl groups.

(I)

Crystal data

C10H12O5·2H2O	F(000) = 528.0
Mr = 248.23	Dx = 1.423 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.7107 Å
Hall symbol: -P 2ybc	Cell parameters from 25 reflections
a = 7.872 (2) Å	θ = 13.7–14.7°
b = 7.560 (2) Å	µ = 0.12 mm^−1
c = 19.836 (2) Å	T = 296 K
β = 101.03 (1)°	Plate, colorless
V = 1158.7 (4) Å^3	0.30 × 0.30 × 0.20 mm
Z = 4

Data collection

Rigaku AFC-5R diffractometer	θmax = 27.5°, θmin = 4°
ω–2θ scans	h = 0→10
3072 measured reflections	k = 0→9
2660 independent reflections	l = −25→25
1259 reflections with I > 2σ(I)	3 standard reflections every 150 reflections
Rint = 0.029	intensity decay: 0.8%

Refinement

Refinement on F^2	H-atom parameters not refined
R[F^2 > 2σ(F^2)] = 0.046	w = 1/[σ^2(Fo^2) + (0.1P)^2] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.175	(Δ/σ)max = 0.001
S = 0.92	Δρmax = 0.25 e Å^−3
2660 reflections	Δρmin = −0.33 e Å^−3
170 parameters

Special details

Refinement. Refinement using reflections with F² > 0.0 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	0.1926 (3)	0.4697 (3)	0.07910 (9)	0.0393 (5)
O2	0.1930 (3)	0.2208 (3)	0.0177 (1)	0.0489 (6)
O3	0.3694 (3)	0.9591 (3)	−0.0636 (1)	0.0466 (6)
O4	0.4363 (3)	0.7937 (2)	−0.17767 (9)	0.0384 (5)
O5	0.3947 (3)	0.4404 (3)	−0.19476 (9)	0.0389 (5)
O6	0.5779 (3)	0.1108 (3)	−0.1840 (1)	0.0447 (6)
O7	0.8956 (4)	0.0726 (3)	−0.0936 (1)	0.0592 (7)
C1	0.2725 (3)	0.4944 (4)	−0.0280 (1)	0.0303 (6)
C2	0.2925 (3)	0.6771 (4)	−0.0181 (1)	0.0324 (6)
C3	0.3451 (4)	0.7785 (3)	−0.0677 (1)	0.0315 (6)
C4	0.3820 (3)	0.7012 (3)	−0.1273 (1)	0.0283 (6)
C5	0.3599 (3)	0.5196 (3)	−0.1373 (1)	0.0278 (6)
C6	0.3063 (4)	0.4162 (4)	−0.0877 (1)	0.0318 (6)
C7	0.2158 (4)	0.3802 (4)	0.0241 (1)	0.0324 (6)
C8	0.1394 (4)	0.3716 (4)	0.1347 (1)	0.0349 (6)
C9	0.1315 (4)	0.4998 (4)	0.1913 (1)	0.0415 (7)
C10	0.0713 (5)	0.4107 (5)	0.2512 (2)	0.0510 (9)
H2	0.2704	0.7293	0.0218	0.0405*
H3	0.3252	0.9987	−0.0325	0.0698*
H4	0.4596	0.8953	−0.1646	0.0576*
H5	0.4102	0.5163	−0.2225	0.0583*
H6	0.2928	0.2948	−0.0941	0.0398*
H8A	0.2221	0.2785	0.1508	0.0436*
H8B	0.0269	0.3181	0.1190	0.0436*
H9A	0.0525	0.5950	0.1740	0.0518*
H9B	0.2452	0.5508	0.2070	0.0518*
H10A	−0.0400	0.3576	0.2355	0.0638*
H10B	0.0628	0.4972	0.2859	0.0638*
H10C	0.1530	0.3211	0.2702	0.0638*
H14	0.542 (5)	0.216 (3)	−0.188 (2)	0.0765*
H15	0.674 (4)	0.117 (5)	−0.156 (2)	0.0765*
H16	0.981 (4)	0.125 (5)	−0.069 (2)	0.0765*
H17	0.884 (5)	−0.021 (4)	−0.070 (2)	0.0765*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.056 (1)	0.037 (1)	0.0301 (10)	−0.0032 (10)	0.0212 (9)	0.0034 (9)
O2	0.076 (2)	0.036 (1)	0.041 (1)	−0.012 (1)	0.027 (1)	−0.0013 (9)
O3	0.078 (2)	0.026 (1)	0.040 (1)	−0.006 (1)	0.024 (1)	−0.0075 (9)
O4	0.060 (1)	0.0259 (10)	0.0329 (10)	−0.0054 (10)	0.0189 (9)	−0.0012 (8)
O5	0.063 (1)	0.0275 (10)	0.033 (1)	−0.0008 (9)	0.0243 (10)	−0.0016 (8)
O6	0.067 (2)	0.027 (1)	0.042 (1)	−0.004 (1)	0.016 (1)	0.0005 (9)
O7	0.079 (2)	0.046 (1)	0.052 (1)	−0.010 (1)	0.009 (1)	0.003 (1)
C1	0.033 (1)	0.032 (1)	0.027 (1)	−0.001 (1)	0.008 (1)	0.003 (1)
C2	0.036 (2)	0.036 (1)	0.027 (1)	−0.001 (1)	0.010 (1)	−0.003 (1)
C3	0.038 (2)	0.025 (1)	0.031 (1)	−0.002 (1)	0.005 (1)	−0.004 (1)
C4	0.031 (1)	0.028 (1)	0.027 (1)	−0.001 (1)	0.007 (1)	0.002 (1)
C5	0.031 (1)	0.027 (1)	0.026 (1)	0.003 (1)	0.007 (1)	−0.001 (1)
C6	0.037 (2)	0.025 (1)	0.035 (1)	−0.003 (1)	0.009 (1)	−0.001 (1)
C7	0.034 (2)	0.036 (2)	0.029 (1)	−0.003 (1)	0.008 (1)	0.003 (1)
C8	0.042 (2)	0.037 (1)	0.029 (1)	−0.002 (1)	0.016 (1)	0.005 (1)
C9	0.054 (2)	0.042 (2)	0.031 (1)	−0.007 (1)	0.014 (1)	0.001 (1)
C10	0.066 (2)	0.057 (2)	0.034 (2)	0.001 (2)	0.021 (2)	0.005 (1)

Geometric parameters (Å, º)

O1—C7	1.326 (3)	C2—C3	1.373 (4)
O1—C8	1.456 (4)	C2—H2	0.930
O2—C7	1.221 (4)	C3—C4	1.397 (4)
O3—C3	1.379 (3)	C4—C5	1.393 (4)
O3—H3	0.820	C5—C6	1.385 (4)
O4—C4	1.354 (3)	C6—H6	0.930
O4—H4	0.820	C8—C9	1.493 (4)
O5—C5	1.362 (3)	C8—H8A	0.970
O5—H5	0.820	C8—H8B	0.970
O6—H14	0.84 (2)	C9—C10	1.519 (4)
O6—H15	0.85 (4)	C9—H9A	0.970
O7—H16	0.85 (4)	C9—H9B	0.970
O7—H17	0.86 (3)	C10—H10A	0.960
C1—C2	1.400 (4)	C10—H10B	0.960
C1—C6	1.393 (4)	C10—H10C	0.960
C1—C7	1.480 (4)
O1···C5^i	3.491 (3)	O4···O6^vii	3.056 (3)
O1···C4^i	3.546 (3)	O4···O5^vii	3.270 (3)
O1···O7^i	3.552 (3)	O4···C8^i	3.514 (4)
O2···O7^ii	2.842 (3)	O4···C9^viii	3.545 (3)
O2···O3^iii	3.049 (3)	O5···O6^vii	2.773 (3)
O2···O7^iv	3.104 (3)	O7···C8^ii	3.454 (4)
O2···C3^i	3.581 (4)	O7···C2^i	3.456 (4)
O3···O3^v	2.997 (4)	C1···C1^i	3.543 (5)
O3···O6^vi	3.349 (3)	C2···C6^i	3.512 (4)
O3···C6^vi	3.511 (3)	C4···C7^i	3.481 (4)
O4···O6^vi	2.657 (3)
C7—O1—C8	117.9 (2)	C5—C6—H6	120.1
C3—O3—H3	109.5	O1—C7—O2	123.3 (3)
C4—O4—H4	109.5	O1—C7—C1	112.6 (2)
C5—O5—H5	109.5	O2—C7—C1	124.1 (3)
H14—O6—H15	104 (4)	O1—C8—C9	107.4 (2)
H16—O7—H17	103 (4)	O1—C8—H8A	110.3
C2—C1—C6	120.2 (2)	O1—C8—H8B	110.2
C2—C1—C7	121.2 (2)	C9—C8—H8A	110.2
C6—C1—C7	118.5 (2)	C9—C8—H8B	110.2
C1—C2—C3	119.5 (2)	H8A—C8—H8B	108.5
C1—C2—H2	120.3	C8—C9—C10	111.4 (3)
C3—C2—H2	120.3	C8—C9—H9A	109.3
O3—C3—C2	124.6 (2)	C8—C9—H9B	109.3
O3—C3—C4	114.6 (2)	C10—C9—H9A	109.3
C2—C3—C4	120.8 (2)	C10—C9—H9B	109.3
O4—C4—C3	123.7 (2)	H9A—C9—H9B	108.0
O4—C4—C5	116.9 (2)	C9—C10—H10A	109.5
C3—C4—C5	119.5 (2)	C9—C10—H10B	109.5
O5—C5—C4	120.9 (2)	C9—C10—H10C	109.5
O5—C5—C6	119.0 (2)	H10A—C10—H10B	109.5
C4—C5—C6	120.2 (2)	H10A—C10—H10C	109.5
C1—C6—C5	119.8 (2)	H10B—C10—H10C	109.5
C1—C6—H6	120.1
O1—C7—C1—C2	−1.6 (3)	O5—C5—C6—C1	179.1 (2)
O1—C7—C1—C6	178.2 (2)	C1—C2—C3—C4	−1.3 (4)
O1—C8—C9—C10	178.2 (2)	C1—C6—C5—C4	0.7 (4)
O2—C7—O1—C8	0.8 (4)	C1—C7—O1—C8	−179.0 (2)
O2—C7—C1—C2	178.6 (3)	C2—C1—C6—C5	0.0 (4)
O2—C7—C1—C6	−1.5 (4)	C2—C3—C4—C5	2.0 (4)
O3—C3—C2—C1	−179.9 (2)	C3—C2—C1—C6	0.2 (4)
O3—C3—C4—O4	−0.4 (4)	C3—C2—C1—C7	−179.9 (2)
O3—C3—C4—C5	−179.2 (2)	C3—C4—C5—C6	−1.7 (4)
O4—C4—C3—C2	−179.2 (2)	C5—C6—C1—C7	−179.8 (2)
O4—C4—C5—O5	1.0 (3)	C7—O1—C8—C9	177.1 (2)
O4—C4—C5—C6	179.4 (2)	C7—O1—C8—C9	177.1 (2)
O5—C5—C4—C3	180.0 (2)

Symmetry codes: (i) −x+1, −y+1, −z; (ii) −x+1, −y, −z; (iii) x, y−1, z; (iv) x−1, y, z; (v) −x+1, −y+2, −z; (vi) x, y+1, z; (vii) −x+1, y+1/2, −z−1/2; (viii) x, −y+3/2, z−1/2.

Hydrogen-bond geometry (º)

D—H···A	D—H···A
O4—H4···O3	113
O5—H5···O4	113
O3—H3···O2^vi	152
O5—H5···O6^vii	155
O6—H14···O5	168 (4)
O6—H15···O7	168 (4)
O7—H16···O2^ix	166 (4)
O7—H17···O2^ii	167

Symmetry codes: (ii) −x+1, −y, −z; (vi) x, y+1, z; (vii) −x+1, y+1/2, −z−1/2; (ix) x+1, y, z.