Molecular packing modes. Part XI. Crystal structures of the 2:1 complexes of benzamide with succinic acid and furamide with oxalic acid

The benzamide–succinic acid adduct (I) crystallises in space group P21/c, with Z= 2 in a unit cell of dimensions: a= 9·194, b= 5·116, c= 19·480 Å, β= 105·66°. The structure was refined from three-dimensional film data to R 0·10 (1441 reflections). The furamide–oxalic acid adduct (II) crystallises in space group P, with Z= 1 in a unit cell of dimensions: a= 7·459, b= 6·579, c= 8·064 Å, α= 92·19, β= 95·60, γ= 120·29°. The structure was refined from three-dimensional counter data to R= 0·015 (1451 reflections).Both (I) and (II) form 2:1 molecular-complex units in which the amide and carboxy-groups are linked by cyclic hydrogen-bonded (asymmetric) pairs [(I) : O–H ⋯ O 2·60, N–H ⋯ O 2·98; (II) : O–H ⋯ O 2·53, N–H ⋯ O 2·92 Å]. The units of (I) are interlinked, along the 5 Å axis, by amide–amide hydrogen bonds (N–H ⋯ O 3·02 Å). Those of (II) are joined, along the 6·6 Å axis, by bifurcated N–H ⋯ O bonds [N–H ⋯ O(hydroxy) 3·10, N–H ⋯ O(carbonyl) 2·94 Å] between the furamide and oxalic acid fragments.