O- and m-Benzenedicarbaldehyde.

o-Benzenedicarbaldehyde (systematic name: benzene-1,2-dicarbaldehyde), C(8)H(6)O(2), exhibits a weak intramolecular hydrogen bond between an aldehyde H atom and the O atom of the adjacent aldehyde group, with a C.O distance of 2.852 (2) A. m-Benzenedicarbaldehyde (systematic name: benzene-1,3-dicarbaldehyde), C(8)H(6)O(2), occurs as two different isomorphs. In all three crystals, there are intermolecular C-H.O contacts involving both aldehyde and ring H atoms.