2,4-Dichlorobenzaldehyde

In the crystal structure of the title compound, C7H4Cl2O, the molecules form a network of weak C—H⋯O interactions involving the aldehyde O atom and the ortho-H atom on the benzene ring together with C—H⋯O interactions between the formyl groups. Together, these connect the molecules into (10) layers, which are stabilized additionally by π–π stacking interactions of the benzene rings [centroid–centroid distance = 3.772 (1) Å]. The aldehyde group is twisted relative to the benzene ring by 7.94 (13)°.

In the crystal structure of the title compound, C 7 H 4 Cl 2 O, the molecules form a network of weak C-HÁ Á ÁO interactions involving the aldehyde O atom and the ortho-H atom on the benzene ring together with C-HÁ Á ÁO interactions between the formyl groups. Together, these connect the molecules into (101) layers, which are stabilized additionally bystacking interactions of the benzene rings [centroid-centroid distance = 3.772 (1) Å ]. The aldehyde group is twisted relative to the benzene ring by 7.94 (13) .
This work was supported by contract GI11496 from HKL Research, Inc.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: GK2246). Comment 2,4-Dichlorobenzaldehyde is primarily used in the preparation of dyes, insecticides, herbicides, antiseptics and disinfectants (Wang et al., 2004). It is also used as an intermediate of organic synthesis of fungicide diniconazole (Katagi, 1988).
The change of the position of chlorine atom causes that interactions in which chlorine atoms are involved in 2,4-dichlorobenzaldehyde and 2,6-dichlorobenzaldehyde differ significantly. In the case of 2,6-dichlorobenzaldehyde Cl2 was involved in weak interaction with hydrogen atom from neighboring benzene ring, while in 2,4-dichlorobenzaldehyde structure such interactions are not observed for any of the chlorine atoms. However, in the case of 2,4-dichlorobenzaldehyde, the chlorine atoms from neighboring molecules form short contacts with Cl1···Cl2 (1/2 + x,1/2 -y,1/2 + z) distance being 3.442Å (Fig. 2).

Refinement
All hydrogen atoms were localized using the difference density Fourier map. Their positions and isotropic displacement parameters were refined.