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organic compounds
Molecules in the title compound, C11H10O4, occur as centrosymmetric dimers, which lie in parallel planes separated by about 1 Å. Both intra- and intermolecular hydrogen bonding occurs across the –OHO=C groups of the dimer, in a rhombic arrangement. The non-H atoms are effectively planar in each momomeric unit, with the ethyl groups lying in an extended trans-configuration. A theoretical study of the equilibrium structures of both the monomeric and dimeric units was made by SCF (self-consistent field) methods with a double-ζ basis set. The monomeric and dimeric structures obtained are very similar to each other, and to the observed structure.