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

Hasan Tanak; Ferda Erşahin; Erbil Ağar; Metin Yavuz; Orhan Büyükgüngör

doi:10.1107/S1600536809033637

. 2009 Aug 29;65(Pt 9):o2291. doi: 10.1107/S1600536809033637

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

Hasan Tanak ^a,^*, Ferda Erşahin ^b, Erbil Ağar ^b, Metin Yavuz ^a, Orhan Büyükgüngör ^a

PMCID: PMC2969980 PMID: 21577683

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 ▶); Barton & Ollis (1979 ▶); Layer (1963 ▶); Ingold (1969 ▶); Cohen et al. (1964 ▶); Moustakali-Mavridis et al. (1978 ▶); Taggi et al. (2002 ▶). For hydrogen-bond motifs, see: Bernstein et al. (1995 ▶). For a related structure, see: Köysal et al. (2007 ▶).

Experimental

Crystal data

C₁₆H₁₇NO
M _r = 239.31
Monoclinic,
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 ▶) 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
Δρ_max = 0.10 e Å⁻³
Δρ_min = −0.14 e Å⁻³

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

Supplementary Material

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

e-65-o2291-sup1.cif^{(18.5KB, cif)}

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

e-65-o2291-Isup2.hkl^{(131.4KB, hkl)}

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

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1⋯N1	0.98 (2)	1.65 (2)	2.5883 (16)	157.3 (18)

Open in a new tab

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).