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Acta Cryst. (2008). E64, o1728    [ doi:10.1107/S1600536808024811 ]

N-(2,6-Diisopropylphenyl)formamide

J. M. Chitanda, J. W. Quail and S. R. Foley

Abstract top

The title compound, C13H19NO, exhibits a non-planar structure in which the 2,6-diisopropylphenyl ring is tilted at a dihedral angle of 77.4 (1)° with respect to the formamide group. This is the largest dihedral angle known among structurally characterized formamides. The molecules are linked via N-H...O hydrogen bonds, forming infinite chains which run along the b-axis directions.

Comment top

As part of the ongoing research in our laboratory directed at the synthesis substituted iminoisoindolines (Chitanda et al., 2008), the title compound was obtained as a by-product and then purposefully synthesized in 92% yield. N-(2,6-diisopropylphenyl)formamide has been previously reported (Krishnamurthy, 1982), however no X-ray structure nor NMR data has been previously published. We have now determined the single-crystal X-ray structure of the title compound, (I).

The 1H NMR (CDCl3) spectra of I is a mixture of two carbon-nitrogen bond rotomers, where the ratio of the major rotomer to the minor rotomer is about 2:1. Upon crystallization however, the solid state structure shows exclusive formation of the cisoidal rotomer. As shown in Figure 1, the carbonyl group on the formamide moiety is positioned almost perpendicular to the plane of the aromatic ring, and is oriented cis to the aromatic group about the carbon-nitrogen bond. The dihedral angle between the plane of the aromatic ring and that formed by the N—C=O moiety is 77.4 (1)°, which is considerably larger than the corresponding angle in previously structurally characterized aryl-substituted formamides (Figure 3). This is attributed to the presence of the bulky isopropyl groups on the ortho positions of the phenyl ring which increases torsional strain between the two planes defining the dihedral angle. For example, in the less bulky analogue, N-(4-methoxyphenyl)formamide, the dihedral angle is only 8.0 (3)° (Figure 3, Cerecetto et al., 2004). The two isomers of the title compound arise due to hindered rotation about the amidic bond (LaPlanche et al., 1964). (I) crystallizes in the monoclinic space group P21/c. The molecules of (I) are linked to form infinite chains which run along the b axis direction via N—H···O hydrogen bonds (details in Table 3).

Related literature top

For related literature, see: Boeyens et al. (1988); Ferguson et al. (1998); Gowda et al. (2000); Krishnamurthy (1982); LaPlanche & Rogers (1964); Omondi et al. (2005); Cerecetto et al. (2004); Chitanda et al. (2008).

Experimental top

The refined procedure for the synthesis of (I) is as follows: A solution of 2,6-diisopropyl aniline (4.695 g, 26.5 mmol s) and formic acid (7.314 g, 159.0 mmol, 6eq.) in chloroform (20 ml) was refluxed with continuous stirring for 16 hrs. The colour of the solution changed from yellow to green to colorless over the course of the reaction. The solvent and excess formic acid were removed under vacuum to yield the title compound as a white solid. Needle-like single crystals suitable for X-ray analysis were obtained from slow evaporation of a chloroform solution (5.00 g, 92%). 1H-NMR (CDCl3, p.p.m.): Two rotomers observed in 2:1 ratio. Major Rotomer: δ 1.19 (d, J = 6.9 Hz, 12H, –CH(CH3)2), δ 3.08 (septet, J = 6.9 Hz, 2H, –CH(CH3)2) δ 6.64 (s(br), 1H, –NH–), δ 7.17 (m, 2H, aromatic), δ 7.30 (m, 1H, aromatic), δ 8.47 (s, 1H, –C(H)=O). 13C-NMR (CDCl3, p.p.m.): δ 23.74 (CH(CH3)2), d 28.9 (–CH(CH3)2), d 123.6, δ 128.7, δ 129.9, δ 146.2, δ 161.0 (–C(H)=O). Minor Rotomer: δ 1.20 (d, J = 6.9 Hz, 12H, –CH(CH3)2), δ 3.20 (septet, J = 6.9 Hz, 2H, –CH(CH3)2) δ 7.02 (d, J = 11.2 Hz, 1H, –NH–), δ 7.19 (m, 2H, aromatic), δ 7.30 (m, 1H, aromatic), δ 8.0 (d, J = 11.2 Hz, 1H, –C(H)=O). 13C-NMR (CDCl3, p.p.m.), Major Rotomer: δ 23.77 (–CH(CH3)2), δ 28.6 (–CH(CH3)2), δ 123.9, δ 129.0, δ 130.4, δ 146.9, δ 165.9 (–C(H)=O). ESI-MS (m/z): calcd. for C13H19NO; 205.1467, 206.1545 [M+H]+; found; 206.1546 [M+H]+.

Refinement top

The hydrogen atoms in the ammonium ions in (II) and (IV) were all found in ΔF maps. The hydrogen atoms were placed in calculated tetrahedral positions on the N atoms (N—H = 0.95 Å). The Uiso of each H atom was assigned as equal to 1.5 times the Ueq of the attached N atom.

Computing details top

Data collection: COLLECT (Nonius, 1998); cell refinement: SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO and SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The molecular structure of (I), showing the atom-labeling scheme. Thermal ellipsoids are drawn at the 50% probability level.
[Figure 2] Fig. 2. The packing of (I), with hydrogen bonds shown as dashed lines. For clarity, H-atoms have been omitted.
[Figure 3] Fig. 3. Dihedral angle of previously characterized aryl-substituted formamides
N-(2,6-Diisopropylphenyl)formamide top
Crystal data top
C13H19NOF000 = 448
Mr = 205.29Dx = 1.137 Mg m−3
Monoclinic, P21/cMo Kα radiation
λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 5165 reflections
a = 8.9581 (15) Åθ = 1.0–27.5º
b = 8.7684 (15) ŵ = 0.07 mm−1
c = 15.840 (6) ÅT = 173 (2) K
β = 105.381 (10)ºRod, colourless
V = 1199.6 (5) Å30.25 × 0.05 × 0.05 mm
Z = 4
Data collection top
Nonius KappaCCD diffractometer2365 independent reflections
Radiation source: fine-focus sealed tube1556 reflections with I > 2σ(I)
Monochromator: horizonally mounted graphite crystalRint = 0.070
Detector resolution: 9 pixels mm-1θmax = 26.0º
T = 173(2) Kθmin = 2.4º
φ scans and ω scans with κ offsetsh = −11→11
Absorption correction: nonek = −10→10
7758 measured reflectionsl = −17→19
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.054H-atom parameters constrained
wR(F2) = 0.128  w = 1/[σ2(Fo2) + (0.0512P)2 + 0.2338P]
where P = (Fo2 + 2Fc2)/3
S = 1.05(Δ/σ)max < 0.001
2365 reflectionsΔρmax = 0.16 e Å−3
140 parametersΔρmin = −0.20 e Å−3
Primary atom site location: structure-invariant direct methodsExtinction correction: none
Crystal data top
C13H19NOV = 1199.6 (5) Å3
Mr = 205.29Z = 4
Monoclinic, P21/cMo Kα
a = 8.9581 (15) ŵ = 0.07 mm−1
b = 8.7684 (15) ÅT = 173 (2) K
c = 15.840 (6) Å0.25 × 0.05 × 0.05 mm
β = 105.381 (10)º
Data collection top
Nonius KappaCCD diffractometer2365 independent reflections
Absorption correction: none1556 reflections with I > 2σ(I)
7758 measured reflectionsRint = 0.070
Refinement top
R[F2 > 2σ(F2)] = 0.054140 parameters
wR(F2) = 0.128H-atom parameters constrained
S = 1.05Δρmax = 0.16 e Å−3
2365 reflectionsΔρmin = −0.20 e Å−3
Special details top

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 (Å2) top
xyzUiso*/Ueq
N10.51988 (18)0.05926 (16)0.22728 (10)0.0277 (4)
H10.5445−0.03800.22820.033*
O10.40304 (16)0.24069 (14)0.29095 (9)0.0385 (4)
C10.5662 (2)0.15772 (18)0.16592 (12)0.0253 (4)
C20.7219 (2)0.20161 (19)0.18370 (13)0.0276 (5)
C30.7655 (2)0.2939 (2)0.12239 (14)0.0311 (5)
H30.87010.32600.13290.037*
C40.6582 (2)0.3389 (2)0.04654 (14)0.0326 (5)
H40.68980.40120.00530.039*
C50.5059 (2)0.2940 (2)0.03028 (13)0.0319 (5)
H50.43370.3255−0.02230.038*
C60.4557 (2)0.20300 (19)0.08966 (12)0.0267 (4)
C70.2869 (2)0.1551 (2)0.06884 (13)0.0327 (5)
H70.27440.08660.11700.039*
C80.2398 (3)0.0654 (3)−0.01662 (16)0.0514 (7)
H8A0.13200.0322−0.02730.062*
H8B0.3069−0.0241−0.01250.062*
H8C0.25040.1304−0.06500.062*
C90.1804 (2)0.2920 (2)0.06525 (17)0.0460 (6)
H9A0.07360.25660.05640.055*
H9B0.18670.35870.01670.055*
H9C0.21250.34870.12040.055*
C100.8387 (2)0.1508 (2)0.26749 (14)0.0349 (5)
H100.81160.04410.28000.042*
C111.0061 (2)0.1496 (3)0.26122 (17)0.0505 (6)
H11A1.07270.10260.31400.061*
H11B1.04040.25450.25600.061*
H11C1.01250.09090.20970.061*
C120.8260 (3)0.2501 (3)0.34482 (15)0.0468 (6)
H12A0.89390.20920.39910.056*
H12B0.71870.24990.34880.056*
H12C0.85730.35480.33600.056*
C130.4417 (2)0.1082 (2)0.28273 (13)0.0309 (5)
H130.41310.03390.31920.037*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0361 (9)0.0177 (7)0.0303 (10)−0.0005 (6)0.0103 (8)0.0028 (6)
O10.0492 (9)0.0278 (7)0.0443 (9)−0.0025 (6)0.0228 (7)−0.0035 (6)
C10.0337 (11)0.0167 (8)0.0276 (11)−0.0004 (7)0.0120 (9)0.0001 (7)
C20.0339 (11)0.0187 (9)0.0328 (12)0.0019 (8)0.0134 (9)−0.0012 (7)
C30.0331 (11)0.0229 (9)0.0415 (13)−0.0020 (8)0.0171 (10)−0.0035 (8)
C40.0464 (13)0.0236 (9)0.0354 (12)0.0022 (9)0.0240 (10)0.0038 (8)
C50.0410 (12)0.0272 (10)0.0284 (11)0.0044 (8)0.0109 (9)0.0027 (8)
C60.0348 (11)0.0205 (9)0.0270 (11)0.0014 (8)0.0120 (9)−0.0018 (7)
C70.0339 (12)0.0314 (10)0.0312 (12)−0.0015 (8)0.0058 (9)0.0026 (8)
C80.0455 (14)0.0435 (13)0.0606 (17)−0.0008 (10)0.0062 (12)−0.0204 (11)
C90.0364 (13)0.0465 (13)0.0544 (16)0.0002 (10)0.0106 (11)−0.0147 (11)
C100.0342 (12)0.0284 (10)0.0394 (13)0.0004 (8)0.0050 (10)0.0049 (9)
C110.0374 (13)0.0464 (13)0.0636 (17)0.0068 (10)0.0065 (12)0.0032 (11)
C120.0397 (13)0.0600 (14)0.0379 (14)−0.0037 (11)0.0052 (11)−0.0007 (11)
C130.0361 (11)0.0271 (10)0.0305 (11)−0.0062 (8)0.0106 (9)0.0022 (8)
Geometric parameters (Å, °) top
N1—C131.331 (2)C7—H71.0000
N1—C11.441 (2)C8—H8A0.9800
N1—H10.8800C8—H8B0.9800
O1—C131.229 (2)C8—H8C0.9800
C1—C61.401 (3)C9—H9A0.9800
C1—C21.402 (3)C9—H9B0.9800
C2—C31.397 (3)C9—H9C0.9800
C2—C101.522 (3)C10—C111.529 (3)
C3—C41.382 (3)C10—C121.532 (3)
C3—H30.9500C10—H101.0000
C4—C51.377 (3)C11—H11A0.9800
C4—H40.9500C11—H11B0.9800
C5—C61.396 (3)C11—H11C0.9800
C5—H50.9500C12—H12A0.9800
C6—C71.520 (3)C12—H12B0.9800
C7—C91.525 (3)C12—H12C0.9800
C7—C81.525 (3)C13—H130.9500
C13—N1—C1123.23 (15)C7—C8—H8C109.5
C13—N1—H1118.4H8A—C8—H8C109.5
C1—N1—H1118.4H8B—C8—H8C109.5
C6—C1—C2122.22 (17)C7—C9—H9A109.5
C6—C1—N1119.19 (16)C7—C9—H9B109.5
C2—C1—N1118.57 (17)H9A—C9—H9B109.5
C3—C2—C1117.78 (18)C7—C9—H9C109.5
C3—C2—C10121.42 (17)H9A—C9—H9C109.5
C1—C2—C10120.80 (16)H9B—C9—H9C109.5
C4—C3—C2120.77 (18)C2—C10—C11113.87 (18)
C4—C3—H3119.6C2—C10—C12110.56 (16)
C2—C3—H3119.6C11—C10—C12109.77 (18)
C5—C4—C3120.46 (18)C2—C10—H10107.5
C5—C4—H4119.8C11—C10—H10107.5
C3—C4—H4119.8C12—C10—H10107.5
C4—C5—C6121.17 (19)C10—C11—H11A109.5
C4—C5—H5119.4C10—C11—H11B109.5
C6—C5—H5119.4H11A—C11—H11B109.5
C5—C6—C1117.59 (18)C10—C11—H11C109.5
C5—C6—C7119.45 (17)H11A—C11—H11C109.5
C1—C6—C7122.95 (16)H11B—C11—H11C109.5
C6—C7—C9111.57 (15)C10—C12—H12A109.5
C6—C7—C8111.09 (17)C10—C12—H12B109.5
C9—C7—C8110.50 (18)H12A—C12—H12B109.5
C6—C7—H7107.8C10—C12—H12C109.5
C9—C7—H7107.8H12A—C12—H12C109.5
C8—C7—H7107.8H12B—C12—H12C109.5
C7—C8—H8A109.5O1—C13—N1125.92 (17)
C7—C8—H8B109.5O1—C13—H13117.0
H8A—C8—H8B109.5N1—C13—H13117.0
C13—N1—C1—C6−77.0 (2)N1—C1—C6—C5−177.80 (15)
C13—N1—C1—C2104.7 (2)C2—C1—C6—C7179.32 (16)
C6—C1—C2—C30.1 (3)N1—C1—C6—C71.1 (3)
N1—C1—C2—C3178.38 (15)C5—C6—C7—C9−64.7 (2)
C6—C1—C2—C10179.73 (16)C1—C6—C7—C9116.4 (2)
N1—C1—C2—C10−2.0 (2)C5—C6—C7—C859.1 (2)
C1—C2—C3—C4−0.5 (3)C1—C6—C7—C8−119.8 (2)
C10—C2—C3—C4179.90 (17)C3—C2—C10—C11−24.2 (3)
C2—C3—C4—C50.3 (3)C1—C2—C10—C11156.20 (17)
C3—C4—C5—C60.3 (3)C3—C2—C10—C1299.9 (2)
C4—C5—C6—C1−0.7 (3)C1—C2—C10—C12−79.7 (2)
C4—C5—C6—C7−179.57 (17)C1—N1—C13—O1−2.2 (3)
C2—C1—C6—C50.4 (3)
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
N1—H1···O1i0.882.042.910 (2)171
Symmetry codes: (i) −x+1, y−1/2, −z+1/2.
Table 1
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
N1—H1···O1i0.882.042.910 (2)171
Symmetry codes: (i) −x+1, y−1/2, −z+1/2.
Acknowledgements top

Financial assistance for this project was provided by the Natural Sciences and Engineering Research Council of Canada (NSERC) for an operating grant to SRF, and by the Canadian Government through the Commonwealth Scholarship fund for JMC.

references
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