5-Amino-1-phenyl-1H-pyrazole-4-carboxylic acid

In the mol­ecule of the title compound, C₁₀H₉N₃O₂, the pyrazole ring is approximately coplanar with the amino and carboxyl groups. The phenyl group is twisted by 48.13 (3)° relative to this plane. An intra­molecular N—H...O hydrogen bond stabilizes the planar conformation of the mol­ecule. The mol­ecules are linked into two-dimensional sheets by two strong inter­molecular N—H...N and O—H...O hydrogen bonds. The latter forms the classic carboxylic acid dimer motif.

Key indicators

• Single-crystal X-ray study
• T = 150 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.043
• wR factor = 0.117
• Data-to-parameter ratio = 19.3

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S1. Comment

Pyrazole and its derivatives are known as heterocyclic compounds, having a wide range of biological activities. Some pyrazoles have been reported to possess significant antiarrhythmic and sedative (Bruno et al., 1990), hypoglycemic (Cottineau et al., 2002), antiviral (Baraldi et al., 1998), and pesticidal (Londershausen,1996) activities. Some of their derivatives have also been successfully tested for their antifungal (Chen & Li, 1998), antihistaminic (Mishra et al., 1998) and anti-inflammatory (Smith et al., 2001) activities. In addition, they have also been used as ligands to investigate the structure–activity relationship of the active site of metalloproteins (Dardari et al., 2006) and for the preparation of some commercially important dyestuffs (Baroni & Kovyrzina, 1961; Neunhoeffer et al., 1959).

As part of our ongoing research on the synthesis and biological evaluation of heterocyclic compounds (Zia-ur-Rehman et al., 2005, 2006; Siddiqui et al., 2007), the crystal structure of the title compound, (I), was determined. In (I), the pyrazole ring is approximately co-planar with the amino and carboxylic acid groups. The C—N bond lengths in the pyrazole ring are 1.3146 (18) and 1.3530 (16) Å, which are shorter than a typical C—N single bond length of 1.443 Å, but longer than a typical C—N bond length of 1.269 Å (Jin et al., 2004), indicating electron delocalization. Most of the bond lengths and angles in N-phenylpyrazole group are in consistent with those in similar molecules (Li et al., 2006; Zhong et al., 2006). Each molecule exhibits an intramolecular N—H···O hydrogen bond which stabilizes the planar conformation and is linked to an adjacent one through head-to-tail pairs of O—H···O intermolecular interactions giving rise to dimeric motifs typical for carboxylic acids. Neighbouring dimers are further arranged into two-dimensional sheets in the (101) plane through N—H···N interactions (Fig.2).

Related literature

For related literature, see: Baroni & Kovyrzina (1961); Baraldi et al. (1998); Bruno et al. (1990); Chen & Li (1998); Cottineau et al. (2002); Dardari et al. (2006); Jin et al. (2004); Li et al. (2006); Londershausen (1996); Mishra et al. (1998); Neunhoeffer et al. (1959); Siddiqui et al. (2007); Smith et al. (2001); Zhong et al. (2006); Zia-ur-Rehman et al. (2005, 2006).

S2. Experimental

A mixture of 5-amino-1-phenyl-1H-pyrazole-4-carboxylic acid, ethyl ester (2.312 g; 10.0 mmoles), potassium hydroxide (1.12 g; 20 mmoles) and ethanol (25 ml) was refluxed for two hours. The reaction mixture was poured into ice cooled water and acidified with dilute hydrochloric acid to Congo Red. The precipitated solids were collected by filtration, washed and dried. Crystals suitable for single-crystal X-ray diffraction were grown by slow evaporation of solution of the title compound in a mixture of ethanol and water (85:15); m.p. 460 K; yield: 68%.

S3. Refinement

H atoms bound to C were placed in geometric positions (C—H distance = 0.95 Å) using a riding model. H atoms on N and O had coordinates freely refined. U_iso values were set to 1.2U_eq (1.5U_eq for OH).

Computing details

Data collection: APEX2 (Bruker, 2006); cell refinement: SAINT (Bruker, 2006); data reduction: SAINT (Bruker, 2006); 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: SHELXTL (Sheldrick, 2008) and local programs.

Figures

	Fig. 1. The asymmetric unit of the title compound. Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. Perspective view of the crystal packing showing hydrogen-bond interactions (dashed lines). H atoms not involved in hydrogen bonding have been omitted for clarity.

5-Amino-1-phenyl-1H-pyrazole-4-carboxylic acid

Crystal data

C10H9N3O2	F(000) = 424
Mr = 203.20	Dx = 1.476 Mg m^−3
Monoclinic, P21/n	Melting point: 460 K
Hall symbol: -P 2yn	Mo Kα radiation, λ = 0.71073 Å
a = 3.7937 (5) Å	Cell parameters from 2299 reflections
b = 21.613 (3) Å	θ = 3.4–29.6°
c = 11.1580 (16) Å	µ = 0.11 mm^−1
β = 92.170 (2)°	T = 150 K
V = 914.2 (2) Å^3	Block, colourless
Z = 4	0.28 × 0.10 × 0.07 mm

Data collection

Bruker APEXII CCD diffractometer	2800 independent reflections
Radiation source: fine-focus sealed tube	1967 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.034
ω rotation with narrow frames scans	θmax = 30.6°, θmin = 1.9°
Absorption correction: multi-scan (SADABS; Sheldrick, 2007)	h = −5→5
Tmin = 0.971, Tmax = 0.993	k = −30→30
10482 measured reflections	l = −15→15

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)] = 0.043	Hydrogen site location: geom except NH & OH coords freely refined
wR(F^2) = 0.116	H atoms treated by a mixture of independent and constrained refinement
S = 1.02	w = 1/[σ^2(Fo^2) + (0.0521P)^2 + 0.3077P] where P = (Fo^2 + 2Fc^2)/3
2800 reflections	(Δ/σ)max < 0.001
145 parameters	Δρmax = 0.34 e Å^−3
0 restraints	Δρmin = −0.27 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
C1	0.0569 (4)	0.34024 (6)	−0.20989 (12)	0.0196 (3)
H1	−0.0345	0.3206	−0.2807	0.023*
C2	0.0428 (4)	0.40410 (7)	−0.19887 (13)	0.0242 (3)
H2	−0.0548	0.4284	−0.2628	0.029*
C3	0.1711 (4)	0.43247 (7)	−0.09461 (14)	0.0262 (3)
H3	0.1623	0.4762	−0.0873	0.031*
C4	0.3122 (4)	0.39693 (7)	−0.00110 (13)	0.0235 (3)
H4C	0.3958	0.4165	0.0707	0.028*
C5	0.3323 (4)	0.33300 (6)	−0.01161 (12)	0.0196 (3)
H5	0.4313	0.3087	0.0522	0.024*
C6	0.2054 (3)	0.30513 (6)	−0.11682 (11)	0.0168 (3)
N2	0.2312 (3)	0.23989 (5)	−0.13188 (9)	0.0172 (2)
N3	0.3587 (3)	0.21589 (5)	−0.23810 (10)	0.0205 (3)
C7	0.3374 (4)	0.15556 (6)	−0.22523 (12)	0.0200 (3)
H7	0.4084	0.1268	−0.2839	0.024*
C8	0.1976 (4)	0.13829 (6)	−0.11488 (11)	0.0175 (3)
C9	0.1300 (3)	0.19438 (6)	−0.05734 (11)	0.0163 (3)
N4	−0.0209 (3)	0.20277 (6)	0.04849 (10)	0.0221 (3)
H4A	−0.068 (5)	0.1668 (8)	0.0857 (15)	0.027*
H4B	−0.028 (5)	0.2377 (8)	0.0881 (16)	0.027*
C10	0.1212 (4)	0.07860 (6)	−0.06630 (12)	0.0198 (3)
O3	−0.0099 (3)	0.07239 (4)	0.03332 (9)	0.0247 (2)
O4	0.1962 (3)	0.03107 (5)	−0.13546 (9)	0.0289 (3)
H4	0.132 (5)	−0.0050 (10)	−0.0983 (17)	0.043*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0207 (7)	0.0229 (7)	0.0153 (6)	0.0004 (5)	0.0039 (5)	0.0023 (5)
C2	0.0263 (7)	0.0229 (7)	0.0239 (7)	0.0054 (6)	0.0068 (6)	0.0071 (5)
C3	0.0298 (8)	0.0172 (6)	0.0324 (8)	−0.0002 (6)	0.0113 (6)	−0.0003 (5)
C4	0.0257 (7)	0.0229 (7)	0.0222 (7)	−0.0043 (5)	0.0052 (5)	−0.0049 (5)
C5	0.0210 (7)	0.0208 (6)	0.0171 (6)	−0.0009 (5)	0.0011 (5)	−0.0005 (5)
C6	0.0183 (6)	0.0163 (6)	0.0161 (6)	−0.0002 (5)	0.0046 (5)	0.0009 (5)
N2	0.0238 (6)	0.0162 (5)	0.0119 (5)	−0.0004 (4)	0.0040 (4)	0.0001 (4)
N3	0.0285 (6)	0.0208 (6)	0.0126 (5)	0.0010 (5)	0.0069 (4)	−0.0007 (4)
C7	0.0266 (7)	0.0192 (6)	0.0144 (6)	0.0006 (5)	0.0042 (5)	−0.0011 (5)
C8	0.0227 (6)	0.0164 (6)	0.0136 (6)	−0.0001 (5)	0.0029 (5)	0.0000 (4)
C9	0.0195 (6)	0.0164 (6)	0.0133 (6)	−0.0004 (5)	0.0013 (5)	0.0009 (4)
N4	0.0348 (7)	0.0168 (5)	0.0153 (5)	−0.0022 (5)	0.0095 (5)	−0.0009 (4)
C10	0.0256 (7)	0.0173 (6)	0.0165 (6)	−0.0001 (5)	0.0034 (5)	−0.0009 (5)
O3	0.0384 (6)	0.0179 (5)	0.0185 (5)	−0.0016 (4)	0.0096 (4)	0.0006 (4)
O4	0.0493 (7)	0.0158 (5)	0.0228 (5)	−0.0021 (5)	0.0157 (5)	−0.0022 (4)

Geometric parameters (Å, º)

C1—C2	1.387 (2)	N2—N3	1.3968 (15)
C1—C6	1.3883 (18)	N3—C7	1.3146 (18)
C1—H1	0.9500	C7—C8	1.4092 (17)
C2—C3	1.387 (2)	C7—H7	0.9500
C2—H2	0.9500	C8—C9	1.4001 (17)
C3—C4	1.387 (2)	C8—C10	1.4331 (18)
C3—H3	0.9500	C9—N4	1.3438 (16)
C4—C5	1.3891 (19)	N4—H4A	0.903 (18)
C4—H4C	0.9500	N4—H4B	0.876 (18)
C5—C6	1.3891 (18)	C10—O3	1.2423 (16)
C5—H5	0.9500	C10—O4	1.3221 (16)
C6—N2	1.4239 (16)	O4—H4	0.92 (2)
N2—C9	1.3530 (16)
C2—C1—C6	119.58 (13)	C9—N2—C6	128.69 (11)
C2—C1—H1	120.2	N3—N2—C6	119.69 (10)
C6—C1—H1	120.2	C7—N3—N2	104.53 (10)
C3—C2—C1	120.06 (13)	N3—C7—C8	112.64 (12)
C3—C2—H2	120.0	N3—C7—H7	123.7
C1—C2—H2	120.0	C8—C7—H7	123.7
C4—C3—C2	119.97 (13)	C9—C8—C7	104.64 (11)
C4—C3—H3	120.0	C9—C8—C10	124.25 (12)
C2—C3—H3	120.0	C7—C8—C10	131.08 (12)
C3—C4—C5	120.55 (13)	N4—C9—N2	125.61 (12)
C3—C4—H4C	119.7	N4—C9—C8	127.68 (12)
C5—C4—H4C	119.7	N2—C9—C8	106.64 (11)
C4—C5—C6	118.97 (13)	C9—N4—H4A	112.7 (11)
C4—C5—H5	120.5	C9—N4—H4B	125.6 (11)
C6—C5—H5	120.5	H4A—N4—H4B	120.0 (16)
C1—C6—C5	120.86 (13)	O3—C10—O4	122.72 (12)
C1—C6—N2	118.73 (12)	O3—C10—C8	121.96 (12)
C5—C6—N2	120.40 (12)	O4—C10—C8	115.31 (12)
C9—N2—N3	111.54 (10)	C10—O4—H4	109.2 (12)
C6—C1—C2—C3	−1.1 (2)	N3—C7—C8—C9	0.05 (16)
C1—C2—C3—C4	−0.3 (2)	N3—C7—C8—C10	178.11 (14)
C2—C3—C4—C5	1.2 (2)	N3—N2—C9—N4	−176.22 (12)
C3—C4—C5—C6	−0.7 (2)	C6—N2—C9—N4	0.3 (2)
C2—C1—C6—C5	1.6 (2)	N3—N2—C9—C8	0.98 (15)
C2—C1—C6—N2	−177.34 (12)	C6—N2—C9—C8	177.55 (13)
C4—C5—C6—C1	−0.7 (2)	C7—C8—C9—N4	176.51 (14)
C4—C5—C6—N2	178.20 (12)	C10—C8—C9—N4	−1.7 (2)
C1—C6—N2—C9	−130.01 (14)	C7—C8—C9—N2	−0.62 (15)
C5—C6—N2—C9	51.1 (2)	C10—C8—C9—N2	−178.85 (13)
C1—C6—N2—N3	46.33 (17)	C9—C8—C10—O3	−0.8 (2)
C5—C6—N2—N3	−132.62 (13)	C7—C8—C10—O3	−178.56 (14)
C9—N2—N3—C7	−0.93 (15)	C9—C8—C10—O4	178.38 (13)
C6—N2—N3—C7	−177.85 (12)	C7—C8—C10—O4	0.7 (2)
N2—N3—C7—C8	0.51 (16)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N4—H4A···O3	0.903 (18)	2.136 (18)	2.8233 (16)	132.3 (14)
N4—H4B···N3^i	0.876 (18)	2.239 (18)	3.0087 (17)	146.5 (15)
O4—H4···O3^ii	0.92 (2)	1.70 (2)	2.6189 (14)	178.4 (19)

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