Crystal structure of 2,4-dinitrophenyl 4-methylbenzenesulfonate: a new polymorph

The title compound, C13H10N2O7S, was solved in the orthorhombic space group Pna21. The aromatic substituents on the sulfonate group are oriented gauche to one another with a C—O—S—C torsion angle of −62.0 (3)°. The supramolecular features that contribute to the crystal lattice are offset π-π and multiple C—H⋯O interactions.


Chemical context
Nucleophilic substitution reactions at the carbonyl carbon atom are an important class of reactions in biological processes. Analogous to the carbonyl group, nucleophilic substitution reactions of sulfonyl derivatives have also been reported (Castro et al., 2003;Terrier et al., 2003;Um et al., 2004Um et al., , 2013Qrareya et al., 2014). The mechanism of nucleophilic substitution reactions at the carbonyl group is well understood (Stefanidis et al., 1993;Lee et al., 2002). However, the mechanism for nucleophilic substitution reactions at the sulfonyl group is not fully understood (Morales-Rojas & Moss, 2002;Um et al., 2013).
A review of the current literature lends credence to both a concerted mechanism and a non-concerted mechanism (Guthrie, 1991;Colthurst & Williams, 1997;Spillane et al., 2001;Um et al., 2003Um et al., , 2004Um et al., , 2013. Using primary and secondary amines as nucleophiles, the factors influencing regioselectivity of nucleophilic substitution reactions at the sulfonyl group have been reported (Um et al., 2004). It has been demonstrated that the regioselectivity and S-O bondfission mechanism depends on the basicity of the amine and the electronic nature of the sulfonyl substituent. Based on the ISSN 2056-9890 current state of knowledge in the field, we have sought to capitalize on the chemistry learned on the mechanistic insight of S-O vs C-O bond fission by investigating the effect of different substituents on the reactivity of sulfonates. In our work, we are interested in using various sulfonate analogues ( Fig. 1) as electrophilic substrates in nucleophilic aromatic substitution (S N Ar) reactions similar to those reported by others (Qrareya et al., 2014). As the title compound is of interest in our ongoing effort on probing the mechanism of S N Ar reactions with sulfonate derivatives, we report here on the synthesis and crystal structure of a new polymorph of 2,4-dinitrophenyl 4-methylbenzenesulfonate (Fig. 2).
For comparison, the polymorph WUVYUH (Vembu et al., 2003a) has S O bond lengths of 1.4204 (10) and 1.4246 (10) Å , and the S-O bond length is 1.6195 (9) Å ( Fig. 2b). While the bond lengths of the two polymorphs agree within 0.01 Å of each other, there are some differences between bond angles. The aromatic rings in WUVYUH are in an anti orientation along the S-O bond, with a torsion angle of 141.02 (9) . The bond angle between the S O groups (O1-S1-O2) is 119.80 (6) , while that of the aromatic substituents (O3-S1-C5) is 98.17 (5) .

Figure 2
(a) The asymmetric unit of the title compound along with the atomnumbering scheme, showing displacement ellipsoids at the 50% probability level; (b) the structure and atom-numbering scheme of a polymorph of the title compound WUVYUH (Vembu, et al., 2003a). All hydrogen atoms have been omitted for clarity. Table 1 Hydrogen-bond geometry (Å , ).

Database survey
The The CSD contains three additional structures where the position ortho to the sulfonic ester bears a nitro group. In FAYBAJ (Manivannan et al., 2005), this o-nitro group is the only substituent. The aromatic ring in XIYZIP is part of a naphthalene system and also bears a 4-nitro group . The third structure in this set is a polymorph of the title compound (WUVYUH: Vembu et al., 2003a) that was solved in the orthorhombic space group Pbca. One significant difference between WUVYUH and the title compound is the orientation of the groups around the S-O bond (see the Structural commentary section for more details). A drawing of a selection of the C-HÁ Á ÁO interactions present in the crystal lattice using a ball and stick model. Symmetry codes: (i) Àx + 1, Ày + 1, z + 1 2 ; (ii) Àx + 3 2 , y + 1 2 , z À 1 2 ; (iii) Àx + 2, Ày + 2, z À 1 2 .

Figure 4
A drawing of the intermolecularstacking and nitro-sulfonic ester interactions present in the crystal using a ball and stick model. Symmetry code (v) Àx + 3 2 , y À 1 2 , z + 1 2 .

Synthesis and crystallization
The title compound was prepared by stirring 2,4-dinitrophenol (5 mmol), p-toluenesulfonyl chloride (5 mmol) and pyridine (3 mmol) in 10 mL of dichloromethane for 30 minutes at room temperature. The reaction was heated to 353 K for 30 minutes in a microwave reactor, then cooled to room temperature and stirred overnight in a fume hood. The reaction mixture was transferred to a scintillation vial where the pale yellow product crystallized upon standing after several days and was filtered from the mother liquor (m.p. 393.4-394.7 K).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. Hydrogen atoms were placed in calculated positions and constrained to ride on their parent atoms, with U iso (H) = 1.2U eq (C) for CH groups and U iso (H) = 1.5 U eq (C) for methyl groups.

Special details
Experimental. SADABS (Bruker, 2014) was used for absorption correction. wR2(int) was 0.0928 before and 0.0535 after correction. The Ratio of minimum to maximum transmission is 0.9202. The λ/2 correction factor is 0.00150. 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.