Monoclinic form of ethyl 4-amino­benzoate (benzocaine)

The structure of the title compound, C₉H₁₁NO₂, (I), comprises a flat mol­ecule arranged, head-to-tail, in linear ribbon arrays via a N—H...O=C association. These ribbons end-on form a herring-bone structure interconnected via N—H...N association. The structure was first determined in 1987 [Sinha & Pattabhi (1987). Proc. Indian Acad. Sci. Chem. Sci. 98, 229–234] in the orthorhombic space group P2₁2₁2₁, with R = 0.120, whereas similar cell dimensions and an increased β angle in the present study resulted in monoclinic space group P2₁/c, with R = 0.065.

Key indicators

• Single-crystal X-ray study
• T = 120 K
• Mean [sigma](C-C) = 0.005 Å
• R factor = 0.065
• wR factor = 0.181
• Data-to-parameter ratio = 12.3

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level B:



REFLT_03
         From the CIF: _diffrn_reflns_theta_max           24.99
         From the CIF: _reflns_number_total               1352
         TEST2: Reflns within _diffrn_reflns_theta_max
         Count of symmetry unique reflns         1542
         Completeness (_total/calc)             87.68%
          Alert B: < 90% complete (theta max?)


 0 Alert Level A = Potentially serious problem

 1 Alert Level B = Potential problem

 0 Alert Level C = Please check

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Computing details

Data collection: DENZO (Otwinowski & Minor, 1997) and COLLECT (Hooft, 1998); cell refinement: DENZO and COLLECT; data reduction: DENZO and COLLECT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON97 (Spek, 1997); software used to prepare material for publication: SHELXL97.

Ethyl 4-aminobenzoate

Crystal data

C9H11NO2	F(000) = 352
Mr = 165.19	Dx = 1.259 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 8.198 (2) Å	Cell parameters from 3445 reflections
b = 5.430 (1) Å	θ = 1.0–27.5°
c = 19.592 (5) Å	µ = 0.09 mm^−1
β = 91.350 (6)°	T = 120 K
V = 871.8 (4) Å^3	Block, colourless
Z = 4	0.10 × 0.08 × 0.03 mm

Data collection

Bruker–Nonius KappaCCD area-detector diffractometer	1352 independent reflections
Radiation source: Bruker–Nonius FR591 rotating anode	686 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.097
Detector resolution: 9.091 pixels mm^-1	θmax = 25.0°, θmin = 2.1°
φ and ω scans	h = −9→9
Absorption correction: multi-scan (SORTAV; Blessing, 1995)	k = −6→5
Tmin = 0.991, Tmax = 0.997	l = −21→23
3445 measured reflections

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)] = 0.065	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.181	H-atom parameters constrained
S = 1.03	w = 1/[σ^2(Fo^2) + (0.0712P)^2] where P = (Fo^2 + 2Fc^2)/3
1352 reflections	(Δ/σ)max < 0.001
110 parameters	Δρmax = 0.22 e Å^−3
0 restraints	Δρmin = −0.24 e Å^−3

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

	x	y	z	Uiso*/Ueq
O1	0.7720 (3)	0.4029 (5)	0.3662 (1)	0.0403 (9)
O2	0.6328 (3)	0.6836 (5)	0.4257 (1)	0.0364 (8)
N1	0.0252 (4)	0.1297 (6)	0.2947 (2)	0.0384 (10)
H11	−0.0644	0.2087	0.3054	0.048*
H12	0.0190	−0.0053	0.2699	0.048*
C1	0.4808 (4)	0.3984 (7)	0.3602 (2)	0.0284 (10)
C2	0.4679 (5)	0.1868 (7)	0.3205 (2)	0.0323 (11)
H2	0.5643	0.1024	0.3081	0.040*
C3	0.3180 (4)	0.0967 (7)	0.2987 (2)	0.0321 (11)
H3	0.3124	−0.0476	0.2714	0.040*
C4	0.1747 (5)	0.2170 (7)	0.3168 (2)	0.0287 (10)
C5	0.1861 (5)	0.4297 (8)	0.3560 (2)	0.0340 (11)
H5	0.0896	0.5142	0.3682	0.042*
C6	0.3370 (4)	0.5200 (7)	0.3775 (2)	0.0322 (11)
H6	0.3428	0.6658	0.4042	0.040*
C7	0.6417 (5)	0.4910 (7)	0.3831 (2)	0.0331 (11)
C8	0.7868 (5)	0.7847 (8)	0.4499 (2)	0.0404 (12)
H71	0.8485	0.8526	0.4113	0.050*
H72	0.8538	0.6557	0.4727	0.050*
C9	0.7458 (5)	0.9862 (7)	0.4998 (2)	0.0401 (12)
H73	0.6718	1.1048	0.4775	0.050*
H74	0.8462	1.0702	0.5148	0.050*
H75	0.6928	0.9141	0.5394	0.050*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0234 (19)	0.047 (2)	0.050 (2)	0.0006 (15)	0.0047 (14)	−0.0056 (15)
O2	0.0260 (17)	0.0366 (18)	0.0464 (19)	−0.0046 (13)	−0.0018 (13)	−0.0087 (15)
N1	0.023 (2)	0.041 (2)	0.050 (2)	0.0043 (16)	−0.0014 (16)	−0.0106 (18)
C1	0.022 (2)	0.027 (3)	0.036 (3)	0.0003 (18)	0.0008 (18)	0.0029 (19)
C2	0.026 (3)	0.038 (3)	0.032 (3)	0.006 (2)	0.0066 (18)	0.002 (2)
C3	0.025 (3)	0.030 (3)	0.041 (3)	−0.0025 (19)	0.001 (2)	−0.0021 (19)
C4	0.022 (2)	0.028 (3)	0.036 (3)	−0.0027 (19)	−0.0016 (18)	0.002 (2)
C5	0.025 (3)	0.031 (3)	0.045 (3)	0.0020 (19)	0.002 (2)	−0.001 (2)
C6	0.026 (3)	0.028 (3)	0.043 (3)	0.0013 (19)	−0.0011 (19)	−0.0017 (19)
C7	0.028 (3)	0.033 (3)	0.038 (3)	−0.003 (2)	0.001 (2)	0.001 (2)
C8	0.023 (3)	0.053 (3)	0.045 (3)	−0.010 (2)	0.001 (2)	−0.001 (2)
C9	0.029 (3)	0.045 (3)	0.047 (3)	−0.004 (2)	−0.005 (2)	−0.005 (2)

Geometric parameters (Å, º)

O1—C7	1.223 (4)	C3—H3	0.95
O2—C7	1.341 (5)	C4—C5	1.389 (5)
O2—C8	1.446 (4)	C5—C6	1.387 (5)
N1—C4	1.374 (4)	C5—H5	0.95
N1—H11	0.88	C6—H6	0.95
N1—H12	0.88	C8—C9	1.511 (5)
C1—C2	1.389 (5)	C8—H71	0.99
C1—C6	1.400 (5)	C8—H72	0.99
C1—C7	1.472 (5)	C9—H73	0.98
C2—C3	1.381 (5)	C9—H74	0.98
C2—H2	0.95	C9—H75	0.98
C3—C4	1.397 (5)
C7—O2—C8	116.1 (3)	C5—C6—C1	120.6 (4)
C4—N1—H11	120.0	C5—C6—H6	119.7
C4—N1—H12	120.0	C1—C6—H6	119.7
H11—N1—H12	120.0	O1—C7—O2	122.2 (4)
C2—C1—C6	118.2 (3)	O1—C7—C1	124.5 (4)
C2—C1—C7	120.6 (4)	O2—C7—C1	113.3 (4)
C6—C1—C7	121.2 (4)	O2—C8—C9	106.3 (3)
C3—C2—C1	121.4 (4)	O2—C8—H71	110.5
C3—C2—H2	119.3	C9—C8—H71	110.5
C1—C2—H2	119.3	O2—C8—H72	110.5
C2—C3—C4	120.3 (4)	C9—C8—H72	110.5
C2—C3—H3	119.9	H71—C8—H72	108.7
C4—C3—H3	119.9	C8—C9—H73	109.5
N1—C4—C5	120.6 (4)	C8—C9—H74	109.5
N1—C4—C3	120.5 (4)	H73—C9—H74	109.5
C5—C4—C3	118.8 (3)	C8—C9—H75	109.5
C6—C5—C4	120.7 (4)	H73—C9—H75	109.5
C6—C5—H5	119.7	H74—C9—H75	109.5
C4—C5—H5	119.7
C6—C1—C2—C3	−0.3 (5)	C7—C1—C6—C5	−179.5 (4)
C7—C1—C2—C3	179.8 (4)	C8—O2—C7—O1	1.1 (5)
C1—C2—C3—C4	−0.5 (6)	C8—O2—C7—C1	−179.6 (3)
C2—C3—C4—N1	179.3 (3)	C2—C1—C7—O1	4.8 (6)
C2—C3—C4—C5	0.9 (5)	C6—C1—C7—O1	−175.2 (4)
N1—C4—C5—C6	−179.1 (4)	C2—C1—C7—O2	−174.5 (3)
C3—C4—C5—C6	−0.7 (6)	C6—C1—C7—O2	5.5 (5)
C4—C5—C6—C1	0.0 (6)	C7—O2—C8—C9	−176.6 (3)
C2—C1—C6—C5	0.5 (6)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H11···O1^i	0.88	2.10	2.934 (4)	158
N1—H12···N1^ii	0.88	2.38	3.252 (3)	174

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