Redetermination of the β-polymorph of p-amino­benzoic acid

Single crystals of p-amino­benzoic acid, C₇H₇NO₂, were grown from water. In the structure, there is one mol­ecule of the acid present in the asymmetric unit. Hydrogen bonds between adjacent mol­ecules lead to the formation of a three-dimensional network.

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.050
• wR factor = 0.131
• Data-to-parameter ratio = 15.5

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT068_ALERT_1_C Reported F000 Differs from Calcd (or Missing)...          ?
PLAT351_ALERT_3_C Long    C-H Bond (0.96A)   C5     -   H5     ...       1.12 Ang.
PLAT355_ALERT_3_C Long    O-H Bond (0.82A)   O1     -   H1     ...       1.06 Ang.
PLAT417_ALERT_2_C Short Inter D-H..H-D       H1     ..  H1A     ..       2.13 Ang.
PLAT420_ALERT_2_C D-H Without Acceptor       N1     -   H1B    ...          ?

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   5 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   1 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   2 ALERT type 2 Indicator that the structure model may be wrong or deficient
   2 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion

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Computing details

Data collection: COLLECT (Nonius, 1999); cell refinement: SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO (Otwinowski & Minor, 1997) and SCALEPACK; program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: maXus (Mackay et al., 1999).

p-aminobenzoic acid

Crystal data

C7H7NO2	Z = 4
Mr = 137.14	Dx = 1.389 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 3547 reflections
a = 6.2782 (3) Å	θ = 4.1–26.4°
b = 8.5831 (4) Å	µ = 0.10 mm^−1
c = 12.3649 (6) Å	T = 298 K
β = 100.133 (2)°	Prism, colourless
V = 655.91 (5) Å^3	0.30 × 0.15 × 0.10 mm

Data collection

Nonius KappaCCD diffractometer	Rint = 0.061
Radiation source: fine-focus sealed tube	θmax = 26.4°, θmin = 4.1°
φ or ω? scans	h = −7→7
6455 measured reflections	k = −10→9
1329 independent reflections	l = −15→15
897 reflections with I > 2σ(I)

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)] = 0.050	H-atom parameters constrained
wR(F^2) = 0.131	w = 1/[σ^2(Fo^2) + (0.0559P)^2 + 0.2521P] where P = (Fo^2 + 2Fc^2)/3
S = 1.03	(Δ/σ)max = 0.001
1329 reflections	Δρmax = 0.14 e Å^−3
86 parameters	Δρmin = −0.19 e Å^−3
0 restraints

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	0.0521 (2)	0.3475 (2)	0.41032 (12)	0.0525 (5)
H1	0.1665	0.4157	0.3769	0.063*
C1	0.1787 (3)	0.3042 (3)	0.50338 (16)	0.0385 (5)
O2	0.3688 (2)	0.3385 (2)	0.52368 (14)	0.0561 (5)
C2	−0.1288 (3)	0.0330 (2)	0.72087 (16)	0.0361 (5)
C3	0.0669 (3)	0.2112 (2)	0.57709 (16)	0.0354 (5)
N1	−0.2305 (3)	−0.0504 (2)	0.79567 (14)	0.0445 (5)
H1A	−0.1295	−0.1007	0.8413	0.053*
H1B	−0.3421	−0.1194	0.7618	0.053*
C4	−0.1426 (3)	0.1544 (3)	0.54428 (17)	0.0393 (5)
H4	−0.2132	0.1803	0.4596	0.047*
C5	0.0778 (3)	0.0930 (3)	0.75496 (18)	0.0430 (5)
H5	0.1591	0.0741	0.8419	0.052*
C6	−0.2391 (3)	0.0649 (3)	0.61529 (17)	0.0406 (5)
H6	−0.3920	0.0099	0.5860	0.049*
C7	0.1743 (3)	0.1804 (3)	0.68364 (17)	0.0420 (5)
H7	0.3354	0.2227	0.7016	0.050*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0427 (9)	0.0723 (12)	0.0402 (9)	−0.0077 (8)	0.0008 (7)	0.0151 (8)
C1	0.0357 (11)	0.0430 (12)	0.0357 (11)	0.0022 (9)	0.0031 (9)	−0.0023 (9)
O2	0.0379 (9)	0.0735 (12)	0.0545 (10)	−0.0108 (8)	0.0016 (7)	0.0118 (8)
C2	0.0394 (11)	0.0336 (11)	0.0366 (11)	0.0008 (9)	0.0105 (9)	−0.0028 (9)
C3	0.0342 (10)	0.0374 (11)	0.0346 (11)	0.0013 (8)	0.0061 (8)	−0.0026 (9)
N1	0.0446 (10)	0.0460 (11)	0.0434 (11)	−0.0044 (8)	0.0093 (8)	0.0021 (9)
C4	0.0374 (12)	0.0466 (13)	0.0333 (11)	−0.0008 (9)	0.0045 (9)	−0.0038 (9)
C5	0.0413 (12)	0.0467 (13)	0.0383 (12)	−0.0016 (10)	−0.0003 (9)	0.0049 (10)
C6	0.0369 (11)	0.0453 (13)	0.0386 (12)	−0.0045 (9)	0.0044 (9)	−0.0053 (10)
C7	0.0366 (11)	0.0462 (13)	0.0412 (12)	−0.0028 (9)	0.0015 (9)	0.0024 (10)

Geometric parameters (Å, º)

O1—C1	1.331 (2)	N1—H1A	0.8837
O1—H1	1.0651	N1—H1B	0.9558
C1—O2	1.212 (2)	C4—C6	1.384 (3)
C1—C3	1.478 (3)	C4—H4	1.0862
C2—C5	1.390 (3)	C5—C7	1.377 (3)
C2—C6	1.393 (3)	C5—H5	1.1173
C2—N1	1.408 (3)	C6—H6	1.0737
C3—C4	1.395 (3)	C7—H7	1.0607
C3—C7	1.396 (3)
C1—O1—H1	98.5	C6—C4—C3	120.36 (19)
O2—C1—O1	121.8 (2)	C6—C4—H4	125.1
O2—C1—C3	124.09 (19)	C3—C4—H4	114.4
O1—C1—C3	114.08 (17)	C7—C5—C2	120.00 (19)
C5—C2—C6	119.63 (19)	C7—C5—H5	121.1
C5—C2—N1	119.74 (18)	C2—C5—H5	118.8
C6—C2—N1	120.48 (18)	C4—C6—C2	120.18 (19)
C4—C3—C7	118.85 (19)	C4—C6—H6	119.7
C4—C3—C1	122.35 (18)	C2—C6—H6	119.8
C7—C3—C1	118.79 (18)	C5—C7—C3	120.9 (2)
C2—N1—H1A	108.1	C5—C7—H7	124.3
C2—N1—H1B	114.2	C3—C7—H7	114.7
H1A—N1—H1B	111.4

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···N1^i	1.07	1.73	2.754 (2)	160
N1—H1A···O2^ii	0.88	2.19	3.045 (2)	164

Symmetry codes: (i) x+1/2, −y+1/2, z−1/2; (ii) −x+1/2, y−1/2, −z+3/2.