Crystal structure of the diglycidyl ether of eugenol

The diepoxy monomer (DGE-Eu) was synthesized from eugenol by a three-step reaction. It consists of a 1,2,4-trisubstituted benzene ring substituted by diglycidyl ether, a methoxy group and a methyloxirane group. The three-membered oxirane rings are inclined to the benzene ring by 61.0 (3) and 27.9 (3)°. In the crystal, molecules are linked by C—H⋯O hydrogen bonds, forming layers parallel to the ab plane.


Chemical context
The past two decades have witnessed an increasing interest in the environmental quest for the replacement of petroleumbased chemicals by monomers from renewable resources. Advances in particular in the catalytic conversion of biomass have led to a wide range of useful platform molecules (Besson et al., 2014). This sustainable approach is also strongly considered in the field of polymer synthesis (Gandini et al., 2016). In the specific domain of epoxy thermosets, numerous studies have been conducted in order to find alternatives to the diglycidyl ether of bisphenol A (BADGE), which is the main building-block used for formulation resins (Auvergne et al., 2014). Classically, the synthetic approach is based on the functionalization of bio-sourced molecules by the grafting of glycidyl ether groups. In this context and in our ongoing studies on the chemical modification of bio-based building blocks for material applications (Mhanna et al., 2014;Bigot et al., 2016;François et al., 2016), we report herein on the synthesis and crystal structure of the diglycidyl ether of eugenol (DGE-Eu), prepared from eugenol in a three-step synthesis (Qin et al., 2014).

Supramolecular features
The crystal packing of DGE-Eu viewed along the c-axis is depicted in Fig. 2. All oxygen atoms of DGE-Eu are involved in C-HÁ Á ÁO hydrogen bonds with surrounding molecules, forming layers lying parallel to the ab plane ( Fig. 2 and Table 1). In addition, the layers are linked C-HÁ Á Á interactions, with the C7-H7A group positioned almost orthogonally to the benzene ring, so forming a three-dimensional network (Table 1 and Fig. 3).
Cg is the centroid of the benzene ring (C1-C6).

Figure 3
Crystal packing of DGE-Eu, viewed along the a axis, showing the layerlike C-HÁ Á ÁO hydrogen-bonded networks linked by C-HÁ Á Á interactions (dashed lines and blue arrows, respectively; see Table 1). For clarity, only H atoms H7B, H11C, H12A, H13B and H7A (grey ball) have been included. Only the major component of atom C12 (C12A) is shown.

Figure 1
A view of the molecular structure of the title compound (DGE-Eu), with the atom labelling. Displacement ellipsoids are drawn at the 50% probability level. The major and minor components of atom C12 (C12A/ C12B) are shown.
(LIPSOS: Cho et al., 1999). In some of these compounds, an epoxy ring is disordered, which is also observed for the title compound DGE-Eu. In terms of application, these compounds are used as precursors of thermosetting resins. The polymerization process involving the epoxy rings occurs in the presence of amines and acid anhydrides and leads to cross-linked rigid materials.

Synthesis and crystallization
The title compound was prepared from a commercial source of eugenol (Sigma-Aldrich), according to a three-step procedure previously reported in the literature (Qin et al., 2014). The details of the synthesis of the title compound are summarized in Fig. 4. Following purification by silica gel column chromatography, colourless prismatic crystals were obtained by slow evaporation of an ethyl acetate solution, and were finally characterized as DGE-Eu.

Refinement details
Crystal data, data collection and structure refinement details are summarized in Table 2. The H atoms were placed at calculated positions and refined using a riding model: C-H = 0.95-1.00 Å with U iso (H) = 1.5U eq (C-methyl) and 1.2U eq (C) for other H atoms. Atom C12 atom of the epoxypropane (oxirane) group (C11/C12/O3) was found to be disordered over two positions with a refined occupancy ratio of 0.69 (1)    program(s) used to solve structure: SHELXT2015 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2015 (Sheldrick, 2015b); molecular graphics: OLEX2 (Dolomanov et al., 2009) and Mercury (Macrae et al., 2008); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (