The crystal structures of four dimethoxybenzaldehyde isomers

The crystal structures of four dimethoxybenzaldehyde (C9H10O3) isomers, namely the 2,3-, 2,4-, 2,5- and 3,5- isomers, are reported and compared to the previously reported crystal structures of 3,4-dimethoxybenzaldehyde and 2,6-dimethoxybenzaldehyde. All dimethoxybenzaldehyde molecules in the crystal structures are nearly planar. The largest deviation (1.2 Å) from the aromatic plane is found for one of the methoxy groups of 2,3-dimethoxybenzaldehyde. Upon rapid cooling of 3,4-dimethoxybenzaldehyde and 3,5-dimethoxybenzaldehyde, a metastable polymorph is formed. The crystal studied for the 3,5- isomer was refined as a two-component twin