N-(4-Fluoro­phen­yl)acetamide

The title compound, C₈H₈FNO, is an important medicinal inter­mediate. Inter­molecular hydrogen bonds are formed between the NH group and the carbonyl O atom of an adjacent mol­ecule.

Key indicators

• Single-crystal X-ray study
• T = 294 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.027
• wR factor = 0.078
• Data-to-parameter ratio = 7.6

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT089_ALERT_3_C Poor Data / Parameter Ratio (Zmax .LT. 18) .....       7.58

Alert level G
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           26.42
           From the CIF: _reflns_number_total                796
           Count of symmetry unique reflns          801
           Completeness (_total/calc)             99.38%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured         0
           Fraction of Friedel pairs measured     0.000
           Are heavy atom types Z>Si present         no

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

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

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S1. Comment

N-(4-Fluorophenyl)acetamide is a useful building block for pharmaceuticals. It was prepared by the reaction of acetic anhydride and 4-fluoroaniline in the presence of triethylamine (Goundwater et al., 1996).

The X-ray crystal structure of the title compound, (I), was carried out in order to elucidate the structure, and the results are presented here. The molecular structure of (I) and the atom-numbering scheme are shown in Fig. 1. In the molecular structure of (I), the N1—C7 bond length [1.338 (3) Å] is longer than that (1.32 Å) for a peptide linkage. The N1—C1 bond length [1.414 (3) Å] is shorter than a normal C—N single bond and longer than a normal C═N double bond, probably as a result of sp²-hybridization between C1 and N1, suggesting that the C1—N1 bond participates in the conjugated system of the benzene ring (Taira et al., 1988).

Intermolecular hydrogen bonds are formed between the NH group and the carbonyl O atom of an adjacent molecule.

S2. Experimental

Acetic anhydride (23.2 ml) was added slowly with stirring to a solution of 4-fluoroaniline (25.0 g) in the presence of triethylamine (25.3 g) at 273 K. The mixture was stirred at room temperature for 3 h. The precipitate formed were filtered off and washed with water three times. A colorless solid (yield 30 g, 86%) was obtained, and single crystals suitable for crystallographic analysis were obtained by slow evaporation of ethyl acetate [m.p. 426 (2) K]. IR (KBr, cm⁻¹): ν 1702. Analysis required for C₈H₈FNO: C 62.7, H 5.3, N 9.2%; found: C 63.0, H 5.4, N 9.3%.

S3. Refinement

All C-bound H atoms were positioned geometrically and refined as riding (C—H = 0.93–0.96 Å). For the CH groups, U_iso(H) values were set equal to 1.2U_eq(carrier atom) and for the methyl groups they were set equal to 1.5U_eq(carrier atom). Treatment of NH group? In the absence of anomalous dispersion effects, the Friedel pairs were merged.

Computing details

Data collection: SMART (Bruker, 1997); cell refinement: SMART; data reduction: SAINT (Bruker, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1997); software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. View of the molecule of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 35% probability level.
	Fig. 2. The intermolecular N—H···O hydrogen bond. [Symmetry codes: (BB) x, y, z; (BA) x, y, z − 1.]

N-(4-Fluorophenyl)acetamide

Crystal data

C8H8FNO	F(000) = 320
Mr = 153.15	Dx = 1.310 Mg m^−3
Monoclinic, Cc	Melting point: 426(2) K
Hall symbol: C -2yc	Mo Kα radiation, λ = 0.71073 Å
a = 4.7307 (15) Å	Cell parameters from 1238 reflections
b = 17.067 (5) Å	θ = 2.4–25.8°
c = 9.634 (3) Å	µ = 0.10 mm^−1
β = 92.871 (5)°	T = 294 K
V = 776.8 (4) Å^3	Prism, colourless
Z = 4	0.24 × 0.20 × 0.14 mm

Data collection

Bruker SMART CCD area-detector diffractometer	796 independent reflections
Radiation source: fine-focus sealed tube	681 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.018
ϕ and ω scans	θmax = 26.4°, θmin = 2.4°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −5→5
Tmin = 0.963, Tmax = 0.986	k = −21→20
2137 measured reflections	l = −12→9

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)] = 0.027	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.078	H atoms treated by a mixture of independent and constrained refinement
S = 1.04	w = 1/[σ^2(Fo^2) + (0.0419P)^2 + 0.1195P] where P = (Fo^2 + 2Fc^2)/3
796 reflections	(Δ/σ)max = 0.002
105 parameters	Δρmax = 0.09 e Å^−3
8 restraints	Δρmin = −0.10 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 > 2σ(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
F1	1.0201 (4)	0.21729 (10)	0.6452 (3)	0.1040 (7)
N1	0.2536 (4)	0.45829 (11)	0.69842 (18)	0.0472 (4)
O1	0.1838 (4)	0.50743 (13)	0.48266 (18)	0.0804 (7)
C1	0.4496 (4)	0.39733 (12)	0.6780 (2)	0.0440 (5)
H1	0.207 (6)	0.4652 (16)	0.782 (3)	0.062 (8)*
C2	0.5455 (5)	0.35617 (14)	0.7945 (3)	0.0573 (6)
H2	0.4808	0.3694	0.8810	0.069*
C3	0.7373 (6)	0.29523 (18)	0.7837 (3)	0.0699 (7)
H3	0.8007	0.2671	0.8619	0.084*
C4	0.8305 (5)	0.27759 (15)	0.6561 (3)	0.0670 (8)
C5	0.7410 (6)	0.31689 (18)	0.5394 (3)	0.0682 (7)
H5	0.8092	0.3033	0.4538	0.082*
C6	0.5485 (5)	0.37702 (16)	0.5488 (3)	0.0589 (6)
H6	0.4847	0.4039	0.4694	0.071*
C7	0.1352 (5)	0.50850 (14)	0.6060 (2)	0.0518 (6)
C8	−0.0605 (6)	0.56781 (15)	0.6638 (3)	0.0700 (7)
H8A	0.0273	0.6185	0.6637	0.105*
H8B	−0.1004	0.5537	0.7573	0.105*
H8C	−0.2337	0.5692	0.6076	0.105*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
F1	0.0839 (12)	0.0771 (12)	0.151 (2)	0.0294 (10)	0.0111 (12)	−0.0181 (12)
N1	0.0578 (10)	0.0535 (10)	0.0307 (8)	0.0032 (9)	0.0062 (7)	−0.0003 (8)
O1	0.1056 (16)	0.0953 (14)	0.0411 (10)	0.0158 (12)	0.0120 (9)	0.0196 (10)
C1	0.0454 (11)	0.0457 (11)	0.0410 (12)	−0.0052 (9)	0.0036 (9)	−0.0047 (9)
C2	0.0634 (15)	0.0601 (14)	0.0487 (12)	0.0057 (12)	0.0060 (11)	0.0050 (11)
C3	0.0702 (17)	0.0656 (17)	0.0734 (18)	0.0078 (14)	0.0005 (14)	0.0115 (14)
C4	0.0518 (15)	0.0538 (14)	0.095 (2)	0.0054 (12)	0.0055 (14)	−0.0109 (14)
C5	0.0626 (16)	0.0749 (17)	0.0682 (16)	0.0000 (13)	0.0147 (13)	−0.0242 (14)
C6	0.0633 (15)	0.0712 (16)	0.0424 (13)	0.0025 (13)	0.0057 (11)	−0.0064 (12)
C7	0.0559 (13)	0.0535 (13)	0.0457 (13)	−0.0053 (11)	−0.0010 (10)	0.0063 (10)
C8	0.0726 (19)	0.0601 (15)	0.0772 (18)	0.0105 (14)	0.0011 (14)	0.0080 (14)

Geometric parameters (Å, º)

F1—C4	1.373 (3)	C3—H3	0.93
O1—C7	1.222 (3)	C4—C5	1.358 (4)
N1—C7	1.338 (3)	C5—C6	1.378 (4)
N1—C1	1.414 (3)	C5—H5	0.93
N1—H1	0.85 (3)	C6—H6	0.93
C1—C2	1.381 (3)	C7—C8	1.498 (4)
C1—C6	1.395 (3)	C8—H8A	0.96
C2—C3	1.388 (4)	C8—H8B	0.96
C2—H2	0.93	C8—H8C	0.96
C3—C4	1.360 (4)
C7—N1—C1	129.36 (19)	C4—C5—C6	119.5 (2)
C7—N1—H1	114.8 (19)	C4—C5—H5	120.2
C1—N1—H1	115.8 (19)	C6—C5—H5	120.2
C2—C1—C6	119.2 (2)	C5—C6—C1	119.7 (2)
C2—C1—N1	116.89 (18)	C5—C6—H6	120.1
C6—C1—N1	123.95 (19)	C1—C6—H6	120.1
C1—C2—C3	120.7 (2)	O1—C7—N1	123.0 (2)
C1—C2—H2	119.7	O1—C7—C8	121.4 (2)
C3—C2—H2	119.7	N1—C7—C8	115.5 (2)
C4—C3—C2	118.4 (3)	C7—C8—H8A	109.5
C4—C3—H3	120.8	C7—C8—H8B	109.5
C2—C3—H3	120.8	H8A—C8—H8B	109.5
C5—C4—C3	122.5 (3)	C7—C8—H8C	109.5
C5—C4—F1	119.0 (3)	H8A—C8—H8C	109.5
C3—C4—F1	118.5 (3)	H8B—C8—H8C	109.5
C7—N1—C1—C2	177.6 (2)	C3—C4—C5—C6	0.0 (4)
C7—N1—C1—C6	−2.6 (3)	F1—C4—C5—C6	179.3 (2)
C6—C1—C2—C3	−0.1 (3)	C4—C5—C6—C1	0.6 (4)
N1—C1—C2—C3	179.8 (2)	C2—C1—C6—C5	−0.5 (3)
C1—C2—C3—C4	0.6 (4)	N1—C1—C6—C5	179.6 (2)
C2—C3—C4—C5	−0.6 (4)	C1—N1—C7—O1	0.7 (4)
C2—C3—C4—F1	−180.0 (2)	C1—N1—C7—C8	−178.5 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O1^i	0.85 (3)	2.00 (3)	2.835 (3)	167 (3)

Symmetry code: (i) x, −y+1, z+1/2.