organic compounds
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In the structure of the 1:1 proton-transfer compound of 4-methylpyridine (γ-picoline) with 4,5-dichlorophthalic acid, C6H8N+·C8H3Cl2O4−·H2O, determined at 200 K, the 4,5-dichlorophthalate anions are bridged by the water molecule through O—HOcarboxyl hydrogen bonds, giving zigzag chains which extend along the c-axis direction. The 4-methylpyridinium cations are linked to the chains through single N—HOwater hydrogen bonds and occupy the voids within the chains in the one-dimensional structure. The anions have the common `planar' conformation with a short intramolecular O—HOcarboxyl hydrogen bond.