1H-Pyrrole-2-carboxylic acid

Abstract

In the title compound, C₅H₅NO₂, the pyrrole ring and its carboxyl substituent are close to coplanar, with a dihedral angle of 11.7 (3)° between the planes. In the crystal structure, adjacent mol­ecules are linked by pairs of O—H⋯O hydrogen bonds to form inversion dimers. Additional N—H⋯O hydrogen bonds link these dimers into chains extending along the a axis.

Related literature

For pyrroles sourced from marine organisms, see: Faulkner (2002 ▶). For the bioactivity of pyrrole derivatives, see: Banwell et al. (2006 ▶); Sosa et al. (2002 ▶). For related structures, see: Zeng (2006 ▶); Zeng et al. (2007 ▶). For graph-set motifs, see: Bernstein et al. (1995 ▶).

Experimental

Crystal data

• C₅H₅NO₂

• M _r = 111.10

• Monoclinic,

• a = 14.080 (3) Å

• b = 5.0364 (10) Å

• c = 14.613 (3) Å

• β = 98.969 (3)°

• V = 1023.6 (3) ų

• Z = 8

• Mo Kα radiation

• μ = 0.11 mm⁻¹

• T = 173 K

• 0.42 × 0.40 × 0.37 mm

Data collection

• Bruker SMART 1K CCD area-detector diffractometer

• Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ▶) T _min = 0.954, T _max = 0.959

• 2277 measured reflections

• 1006 independent reflections

• 875 reflections with I > 2σ(I)

• R _int = 0.015

Refinement

• R[F ² > 2σ(F ²)] = 0.063

• wR(F ²) = 0.191

• S = 1.06

• 1006 reflections

• 74 parameters

• H-atom parameters constrained

• Δρ_max = 0.74 e Å⁻³

• Δρ_min = −0.73 e Å⁻³

Data collection: SMART (Bruker,1999 ▶); cell refinement: SAINT-Plus (Bruker, 1999 ▶); data reduction: SAINT-Plus; 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.

Supplementary Material

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1A⋯O1i	0.88	2.22	2.951 (3)	141
O2—H2A⋯O1ii	0.84	2.16	2.986 (3)	166

Symmetry codes: (i) ; (ii) .

supplementary crystallographic information

Comment

Pyrrole derivatives are well known in many marine organisms (Faulkner, 2002), some show important bioactivities, such as antitumor activity (Banwell et al., 2006) and protein kinase inhibiting activity (Sosa et al., 2002). This is the reason they have attracted our interest. This study is related to our previous structural investigations of methyl 2-(4,5-dibromo-1H-pyrrole-2-carboxamido)propionate (Zeng et al., 2007) and 3-bromo-1-methyl-6,7-dihydropyrrolo[2,3-c]azepine- 4,8(1H,5H)-dione (Zeng, 2006). In the crystal structure, molecules of the title compound are linked through N1—H1···O1ⁱ hydrogen bonds to form centrosymmetric dimers (Fig. 2) of graph-set motif R₂²(10) (Bernstein et al., 1995), which are linked by O2—H2···O1ⁱⁱ hydrogen bonds (another kind of centrosymmetric dimers of graph-set motif R₂²(8) are formed), generating chains extending to the a axis (also shown in Fig. 2).

Experimental

The commercially available 1H-pyrrole-2-carboxylic acid was dissolved in the mixture of EtOH (80%) and ethyl acetate (20%). Colorless monoclinic crystals suitable for X-ray analysis were obtained when the solution was exposed to the air at room temperature for about 5 d.

Refinement

All non-H atoms were refined with anisotropic displacement parameters. The H atoms were positioned geometrically [C—H = 0.95Å for CH, O—H = 0.84Å for OH, and N—H = 0.88 Å] and refined using a riding model, with U_iso = 1.2U_eq (1.5U_eq for the methyl group) of the parent atom. In the final difference Fourier map the highest peak (0.74 eÅ^-3) is 1.01Å from O2 and the deepest hole (-0.73 eÅ^-3) is 0.61Å from O2.

Figures

Fig. 1.

The molecular structure of the title compound, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.

Fig. 2.

Crystal packing of (I) showing the chains formed by hydrogen bonds (dashed lines).

Crystal data

C5H5NO2	F(000) = 464
Mr = 111.10	Dx = 1.442 Mg m−3
Monoclinic, C2/c	Melting point: 480 K
Hall symbol: -C 2yc	Mo Kα radiation, λ = 0.71073 Å
a = 14.080 (3) Å	Cell parameters from 1751 reflections
b = 5.0364 (10) Å	θ = 2.8–27.0°
c = 14.613 (3) Å	µ = 0.11 mm−1
β = 98.969 (3)°	T = 173 K
V = 1023.6 (3) Å3	Block, colorless
Z = 8	0.42 × 0.40 × 0.37 mm

Data collection

Bruker SMART 1K CCD area-detector diffractometer	1006 independent reflections
Radiation source: fine-focus sealed tube	875 reflections with I > 2σ(I)
graphite	Rint = 0.015
φ and ω scans	θmax = 26.0°, θmin = 2.8°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −17→13
Tmin = 0.954, Tmax = 0.959	k = −6→6
2277 measured reflections	l = −14→18

Refinement

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.063	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.191	H-atom parameters constrained
S = 1.06	w = 1/[σ2(Fo2) + (0.1108P)2 + 3.3345P] where P = (Fo2 + 2Fc2)/3
1006 reflections	(Δ/σ)max = 0.001
74 parameters	Δρmax = 0.74 e Å−3
0 restraints	Δρmin = −0.73 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
O1	0.12435 (12)	1.1503 (3)	0.53422 (12)	0.0223 (5)
C4	0.23786 (16)	0.8483 (5)	0.61313 (15)	0.0176 (6)
O2	0.07382 (14)	0.7350 (4)	0.56343 (15)	0.0373 (6)
H2A	0.0220	0.7923	0.5336	0.056*
N1	0.31542 (14)	1.0100 (4)	0.61094 (15)	0.0216 (6)
H1A	0.3144	1.1614	0.5808	0.026*
C3	0.26837 (17)	0.6325 (5)	0.66849 (17)	0.0208 (6)
H3	0.2299	0.4879	0.6828	0.025*
C5	0.14189 (16)	0.9228 (5)	0.56657 (15)	0.0173 (6)
C2	0.36767 (18)	0.6681 (5)	0.69974 (17)	0.0245 (6)
H2	0.4085	0.5521	0.7393	0.029*
C1	0.39405 (17)	0.9010 (6)	0.66242 (18)	0.0251 (6)
H1	0.4570	0.9740	0.6712	0.030*

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
O1	0.0198 (9)	0.0190 (10)	0.0273 (10)	−0.0004 (7)	0.0008 (7)	0.0048 (7)
C4	0.0184 (12)	0.0182 (12)	0.0167 (11)	−0.0004 (9)	0.0039 (9)	−0.0005 (9)
O2	0.0298 (11)	0.0331 (12)	0.0472 (13)	−0.0029 (9)	0.0002 (10)	0.0044 (10)
N1	0.0191 (10)	0.0196 (11)	0.0253 (11)	−0.0027 (8)	0.0013 (8)	0.0062 (8)
C3	0.0210 (12)	0.0198 (12)	0.0216 (12)	0.0003 (9)	0.0035 (9)	0.0020 (9)
C5	0.0192 (12)	0.0164 (11)	0.0167 (11)	−0.0002 (9)	0.0042 (9)	−0.0008 (9)
C2	0.0220 (13)	0.0291 (14)	0.0215 (12)	0.0052 (10)	0.0009 (9)	0.0038 (10)
C1	0.0174 (12)	0.0318 (14)	0.0256 (13)	−0.0013 (10)	0.0019 (9)	0.0030 (11)

Geometric parameters (Å, °)

O1—C5	1.250 (3)	N1—H1A	0.8800
C4—N1	1.367 (3)	C3—C2	1.413 (3)
C4—C3	1.383 (3)	C3—H3	0.9500
C4—C5	1.464 (3)	C2—C1	1.369 (4)
O2—C5	1.342 (3)	C2—H2	0.9500
O2—H2A	0.8400	C1—H1	0.9500
N1—C1	1.354 (3)
N1—C4—C3	107.8 (2)	O1—C5—O2	122.4 (2)
N1—C4—C5	121.3 (2)	O1—C5—C4	121.6 (2)
C3—C4—C5	130.8 (2)	O2—C5—C4	116.0 (2)
C5—O2—H2A	109.5	C1—C2—C3	107.2 (2)
C1—N1—C4	109.4 (2)	C1—C2—H2	126.4
C1—N1—H1A	125.3	C3—C2—H2	126.4
C4—N1—H1A	125.3	N1—C1—C2	108.6 (2)
C4—C3—C2	106.9 (2)	N1—C1—H1	125.7
C4—C3—H3	126.5	C2—C1—H1	125.7
C2—C3—H3	126.5
C3—C4—N1—C1	0.7 (3)	N1—C4—C5—O2	171.9 (2)
C5—C4—N1—C1	177.3 (2)	C3—C4—C5—O2	−12.3 (4)
N1—C4—C3—C2	−0.2 (3)	C4—C3—C2—C1	−0.3 (3)
C5—C4—C3—C2	−176.4 (2)	C4—N1—C1—C2	−0.9 (3)
N1—C4—C5—O1	−10.0 (3)	C3—C2—C1—N1	0.7 (3)
C3—C4—C5—O1	165.7 (2)

Hydrogen-bond geometry (Å, °)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···O1i	0.88	2.22	2.951 (3)	141
O2—H2A···O1ii	0.84	2.16	2.986 (3)	166

Symmetry codes: (i) −x+1/2, −y+5/2, −z+1; (ii) −x, −y+2, −z+1.