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Acta Crystallogr Sect E Struct Rep Online. 2009 September 1; 65(Pt 9): o2291.
Published online 2009 August 29. doi:  10.1107/S1600536809033637
PMCID: PMC2969980

2-[(2,4-Dimethyl­phen­yl)imino­meth­yl]-6-methyl­phenol

Abstract

The title compound, C16H17NO, is a Schiff base which adopts the phenol–imine tautomeric form in the solid state. The mol­ecule is almost planar, with a dihedral angle of 4.61 (4)° between the aromatic rings. The molecular structure is stabilized by an intramolecular O—H(...)N hydrogen bond which generates a six membered ring.

Related literature

For background to the properties and uses of Schiff bases, see: Aydoğan et al. (2001 [triangle]); Barton & Ollis (1979 [triangle]); Layer (1963 [triangle]); Ingold (1969 [triangle]); Cohen et al. (1964 [triangle]); Moustakali-Mavridis et al. (1978 [triangle]); Taggi et al. (2002 [triangle]). For hydrogen-bond motifs, see: Bernstein et al. (1995 [triangle]). For a related structure, see: Köysal et al. (2007 [triangle]).

An external file that holds a picture, illustration, etc.
Object name is e-65-o2291-scheme1.jpg

Experimental

Crystal data

  • C16H17NO
  • M r = 239.31
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-65-o2291-efi1.jpg
  • a = 18.1448 (11) Å
  • b = 4.7141 (3) Å
  • c = 15.7151 (8) Å
  • β = 99.646 (4)°
  • V = 1325.21 (13) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 0.07 mm−1
  • T = 296 K
  • 0.80 × 0.40 × 0.15 mm

Data collection

  • Stoe IPDS II diffractometer
  • Absorption correction: integration (X-RED32; Stoe & Cie, 2002 [triangle]) T min = 0.963, T max = 0.990
  • 18038 measured reflections
  • 2732 independent reflections
  • 1808 reflections with I > 2σ(I)
  • R int = 0.058

Refinement

  • R[F 2 > 2σ(F 2)] = 0.044
  • wR(F 2) = 0.120
  • S = 1.01
  • 2732 reflections
  • 169 parameters
  • H atoms treated by a mixture of independent and constrained refinement
  • Δρmax = 0.10 e Å−3
  • Δρmin = −0.14 e Å−3

Data collection: X-AREA (Stoe & Cie, 2002 [triangle]); cell refinement: X-AREA; data reduction: X-RED32 (Stoe & Cie, 2002 [triangle]); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 [triangle]); software used to prepare material for publication: WinGX (Farrugia, 1999 [triangle]).

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809033637/fl2259sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809033637/fl2259Isup2.hkl

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

Acknowledgments

This study was supported financially by the Research Center of Ondokuz Mayıs University (Project No. F-476). The authors acknowledge the Faculty of Arts and Sciences, Ondokuz Mayıs University, Turkey, for the use of the Stoe IPDS II diffractometer (purchased under grant No. F279 of the University Research Fund).

supplementary crystallographic information

Comment

Schiff bases, i.e., compounds having a double C=N bond, are used as starting materials in the synthesis of important drugs, such as antibiotics, antiallergic, antiphlogistic, and antitumor substances (Barton et al., 1979; Layer, 1963; Ingold 1969). They also have a wide ranage of industrial uses such as dyes and pigments (Taggi et al., 2002). Schiff bases have also been employed as ligands for the complexation of metal ions (Aydoğan et al., 2001). Two characteristic properties of Schiff bases, are photochromism and thermochromism (Cohen et al., 1964). In general, Schiff bases display two possible tautomeric forms, the phenol-imine (OH) and the keto-amine (NH) forms. Depending on the tautomers, two types of intramolecular hydrogen bonds are observed: O—H···N in the phenol-imines and N—H···O in keto-amine tautomers.

In the title compound (I, Fig. 1), the molecule is almost planar with a dihedral angle between the aromatic rings [C1/C6 and C9/C14] of 4.61 (4)°. The imino group is coplanar with the hydroxyphenyl ring as it is shown by the C2—C1—C8—N1 torsion angle of -0.9 (2)°. The O—H and C=N bond lengths confirm that (I) exhibits the enol-imine tautomer. The length of the C8=N1 double bond is 1.272 (2) Å which is slightly shorter than the standard value of 1.28 Å but it is consistent with the related sturucture (Köysal et al., 2007). It is also known that Schiff bases may exhibit thermochromism depending on the planarity or non-planarity of the molecule, respectively (Moustakali-Mavridis et al., 1978). Therefore, the title compound may exhibit thermochromic properties.

The phenol H atom forms a strong intramolecular O1—H1···N1 hydrogen bond with the imine N atom. (Table 1, Fig. 1) which generates a six-membered ring, producing a S(6) ring motif (Bernstein et al., 1995), stabilizing the planarity of the molecular skeleton. A packing diagram for (I) with hydrogen bonding geometry is shown in figure 2.

Experimental

A solution of 3-methylsalicylaldehyde (0.0239 g, 0.1755 mmol) in ethanol (10 ml) was added to a solution of 2,4-dimethylaniline (0.02127 g, 0.1755 mmol) in ethanol (20 ml). The reaction mixture was stirred for 2 h under reflux. Single crystals suitable for X-ray analysis were obtained from ethyl alcohol by slow evaporation (yield 74%; m.p.386–388 K).

Refinement

C-bound H atoms were positioned geometrically and refined using a riding model, with C—H = 0.93–0.96 Å and Uiso(H) = 1.2–1.5Ueq(C). The C16-methyl group was refined as idealized disordered one with two positions rotated from each other by 60°. The position of the H1 atom was obtained from a difference map of the electron density in the unit-cell and was refined freely.

Figures

Fig. 1.
The molecular structure of the title compound, showing the atom-numbering scheme and 30% probability diplacement ellipsoids. The disordered hydrogens on C16 are also shown.
Fig. 2.
The crystal packing of the title compound. Intramolecular hydrogen bonds are shown as dashed lines.

Crystal data

C16H17NOF(000) = 512
Mr = 239.31Dx = 1.199 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 21940 reflections
a = 18.1448 (11) Åθ = 1.6–28.0°
b = 4.7141 (3) ŵ = 0.07 mm1
c = 15.7151 (8) ÅT = 296 K
β = 99.646 (4)°Prism, yellow
V = 1325.21 (13) Å30.80 × 0.40 × 0.15 mm
Z = 4

Data collection

Stoe IPDS II diffractometer2732 independent reflections
Radiation source: fine-focus sealed tube1808 reflections with I > 2σ(I)
graphiteRint = 0.058
Detector resolution: 6.67 pixels mm-1θmax = 26.5°, θmin = 2.3°
rotation method scansh = −22→22
Absorption correction: integration (X-RED32; Stoe & Cie, 2002)k = −5→5
Tmin = 0.963, Tmax = 0.990l = −19→19
18038 measured reflections

Refinement

Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.044Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.120H atoms treated by a mixture of independent and constrained refinement
S = 1.01w = 1/[σ2(Fo2) + (0.0631P)2] where P = (Fo2 + 2Fc2)/3
2732 reflections(Δ/σ)max < 0.001
169 parametersΔρmax = 0.10 e Å3
0 restraintsΔρmin = −0.14 e Å3

Special details

Experimental. 359 frames, detector distance = 100 mm
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)

xyzUiso*/UeqOcc. (<1)
C10.35139 (7)0.4131 (3)0.57205 (9)0.0555 (3)
C20.33187 (7)0.3180 (3)0.64973 (9)0.0568 (4)
C30.37660 (8)0.1210 (3)0.70152 (10)0.0639 (4)
C40.43983 (8)0.0228 (4)0.67355 (10)0.0716 (5)
H40.4698−0.10900.70720.086*
C50.46019 (9)0.1133 (4)0.59720 (11)0.0766 (5)
H50.50330.04360.58000.092*
C60.41638 (8)0.3062 (4)0.54709 (10)0.0704 (4)
H60.43000.36720.49560.084*
C70.35539 (10)0.0258 (5)0.78536 (11)0.0943 (6)
H7A0.3059−0.05320.77480.113*
H7B0.35650.18510.82360.113*
H7C0.3902−0.11550.81130.113*
C80.30616 (8)0.6172 (3)0.51840 (9)0.0588 (4)
H80.32140.67700.46770.071*
C90.20053 (7)0.9169 (3)0.48548 (8)0.0538 (3)
C100.13929 (8)1.0247 (3)0.51850 (9)0.0573 (4)
C110.09298 (8)1.2164 (3)0.46860 (9)0.0614 (4)
H110.05221.28820.49040.074*
C120.10427 (8)1.3069 (3)0.38793 (9)0.0602 (4)
C130.16527 (8)1.1959 (3)0.35699 (10)0.0662 (4)
H130.17451.25160.30300.079*
C140.21240 (8)1.0049 (4)0.40465 (9)0.0659 (4)
H140.25300.93350.38230.079*
C150.12371 (9)0.9339 (4)0.60573 (10)0.0764 (5)
H15A0.16530.98430.64930.092*
H15B0.11640.73220.60610.092*
H15C0.07951.02740.61740.092*
C160.05261 (9)1.5162 (4)0.33607 (10)0.0731 (4)
H16A0.01391.56900.36780.110*0.50
H16B0.03071.43130.28220.110*0.50
H16C0.08031.68180.32510.110*0.50
H16D0.06941.55240.28230.110*0.50
H16E0.05261.69010.36780.110*0.50
H16F0.00291.43950.32500.110*0.50
N10.24618 (6)0.7186 (3)0.53786 (7)0.0577 (3)
O10.27017 (6)0.4153 (3)0.67706 (8)0.0781 (4)
H10.2494 (11)0.542 (5)0.6293 (15)0.128 (8)*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
C10.0539 (7)0.0570 (9)0.0546 (8)−0.0013 (6)0.0063 (6)−0.0050 (6)
C20.0524 (7)0.0602 (9)0.0571 (8)−0.0024 (7)0.0075 (6)−0.0035 (7)
C30.0651 (8)0.0648 (10)0.0588 (8)0.0001 (7)0.0017 (7)−0.0014 (7)
C40.0717 (9)0.0697 (11)0.0674 (10)0.0120 (8)−0.0063 (8)−0.0044 (8)
C50.0661 (9)0.0924 (13)0.0707 (10)0.0237 (9)0.0096 (7)−0.0075 (9)
C60.0661 (9)0.0841 (12)0.0623 (9)0.0124 (8)0.0147 (7)0.0001 (8)
C70.0993 (13)0.1095 (16)0.0736 (12)0.0156 (11)0.0130 (10)0.0261 (11)
C80.0604 (8)0.0627 (10)0.0545 (8)0.0005 (7)0.0127 (6)0.0018 (7)
C90.0549 (7)0.0532 (9)0.0533 (7)−0.0002 (6)0.0091 (6)−0.0012 (6)
C100.0584 (8)0.0607 (9)0.0533 (8)−0.0004 (7)0.0104 (6)−0.0045 (7)
C110.0584 (8)0.0647 (10)0.0609 (8)0.0074 (7)0.0095 (6)−0.0068 (7)
C120.0645 (8)0.0519 (9)0.0614 (8)−0.0012 (7)0.0030 (6)−0.0043 (7)
C130.0730 (9)0.0673 (10)0.0597 (8)0.0018 (8)0.0153 (7)0.0089 (8)
C140.0664 (9)0.0715 (11)0.0635 (9)0.0094 (8)0.0216 (7)0.0067 (8)
C150.0705 (9)0.0992 (13)0.0635 (9)0.0151 (9)0.0227 (7)0.0053 (9)
C160.0745 (10)0.0645 (11)0.0758 (10)0.0069 (8)−0.0003 (8)0.0042 (8)
N10.0568 (7)0.0583 (8)0.0587 (7)0.0037 (5)0.0120 (5)0.0013 (6)
O10.0692 (6)0.0967 (9)0.0732 (7)0.0176 (6)0.0263 (5)0.0192 (7)

Geometric parameters (Å, °)

C1—C61.3975 (19)C10—C111.385 (2)
C1—C21.4005 (19)C10—C151.5073 (19)
C1—C81.442 (2)C11—C121.385 (2)
C2—O11.3452 (17)C11—H110.9300
C2—C31.401 (2)C12—C131.384 (2)
C3—C41.376 (2)C12—C161.503 (2)
C3—C71.502 (2)C13—C141.374 (2)
C4—C51.381 (2)C13—H130.9300
C4—H40.9300C14—H140.9300
C5—C61.367 (2)C15—H15A0.9600
C5—H50.9300C15—H15B0.9600
C6—H60.9300C15—H15C0.9600
C7—H7A0.9600C16—H16A0.9600
C7—H7B0.9600C16—H16B0.9600
C7—H7C0.9600C16—H16C0.9600
C8—N11.2720 (17)C16—H16D0.9600
C8—H80.9300C16—H16E0.9600
C9—C141.3872 (18)C16—H16F0.9600
C9—C101.3985 (18)O1—H10.98 (2)
C9—N11.4172 (17)
C6—C1—C2118.54 (13)C13—C12—C16121.35 (14)
C6—C1—C8120.06 (13)C11—C12—C16121.60 (14)
C2—C1—C8121.40 (12)C14—C13—C12121.17 (14)
O1—C2—C1120.98 (13)C14—C13—H13119.4
O1—C2—C3118.21 (13)C12—C13—H13119.4
C1—C2—C3120.80 (13)C13—C14—C9121.15 (13)
C4—C3—C2118.06 (14)C13—C14—H14119.4
C4—C3—C7121.98 (15)C9—C14—H14119.4
C2—C3—C7119.96 (14)C10—C15—H15A109.5
C3—C4—C5122.17 (15)C10—C15—H15B109.5
C3—C4—H4118.9H15A—C15—H15B109.5
C5—C4—H4118.9C10—C15—H15C109.5
C6—C5—C4119.45 (14)H15A—C15—H15C109.5
C6—C5—H5120.3H15B—C15—H15C109.5
C4—C5—H5120.3C12—C16—H16A109.5
C5—C6—C1120.98 (15)C12—C16—H16B109.5
C5—C6—H6119.5H16A—C16—H16B109.5
C1—C6—H6119.5C12—C16—H16C109.5
C3—C7—H7A109.5H16A—C16—H16C109.5
C3—C7—H7B109.5H16B—C16—H16C109.5
H7A—C7—H7B109.5C12—C16—H16D109.5
C3—C7—H7C109.5H16A—C16—H16D141.1
H7A—C7—H7C109.5H16B—C16—H16D56.3
H7B—C7—H7C109.5H16C—C16—H16D56.3
N1—C8—C1122.44 (13)C12—C16—H16E109.5
N1—C8—H8118.8H16A—C16—H16E56.3
C1—C8—H8118.8H16B—C16—H16E141.1
C14—C9—C10119.08 (13)H16C—C16—H16E56.3
C14—C9—N1124.33 (12)H16D—C16—H16E109.5
C10—C9—N1116.59 (12)C12—C16—H16F109.5
C11—C10—C9118.14 (13)H16A—C16—H16F56.3
C11—C10—C15120.79 (13)H16B—C16—H16F56.3
C9—C10—C15121.07 (13)H16C—C16—H16F141.1
C10—C11—C12123.42 (13)H16D—C16—H16F109.5
C10—C11—H11118.3H16E—C16—H16F109.5
C12—C11—H11118.3C8—N1—C9123.26 (12)
C13—C12—C11117.05 (14)C2—O1—H1101.3 (12)
C6—C1—C2—O1179.58 (14)C14—C9—C10—C11−0.1 (2)
C8—C1—C2—O1−0.3 (2)N1—C9—C10—C11−179.26 (13)
C6—C1—C2—C30.3 (2)C14—C9—C10—C15179.56 (15)
C8—C1—C2—C3−179.57 (13)N1—C9—C10—C150.4 (2)
O1—C2—C3—C4−179.75 (14)C9—C10—C11—C12−0.1 (2)
C1—C2—C3—C4−0.4 (2)C15—C10—C11—C12−179.76 (15)
O1—C2—C3—C7−0.4 (2)C10—C11—C12—C130.2 (2)
C1—C2—C3—C7178.92 (15)C10—C11—C12—C16−179.85 (14)
C2—C3—C4—C50.4 (2)C11—C12—C13—C14−0.1 (2)
C7—C3—C4—C5−178.92 (17)C16—C12—C13—C14179.93 (14)
C3—C4—C5—C6−0.2 (3)C12—C13—C14—C90.0 (3)
C4—C5—C6—C10.0 (3)C10—C9—C14—C130.2 (2)
C2—C1—C6—C5−0.1 (2)N1—C9—C14—C13179.27 (14)
C8—C1—C6—C5179.76 (15)C1—C8—N1—C9−179.25 (13)
C6—C1—C8—N1179.29 (14)C14—C9—N1—C85.4 (2)
C2—C1—C8—N1−0.9 (2)C10—C9—N1—C8−175.44 (14)

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
O1—H1···N10.98 (2)1.65 (2)2.5883 (16)157.3 (18)

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: FL2259).

References

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