N,N′-Bis­[tris­(hydroxy­methyl)­methyl]­ethanedi­amide: six O—H...O hydrogen bonds generate only a two-­dimensional structure

Molecules of the title compound, C₁₀H₂₀N₂O₈, adopt a conformation which is almost centrosymmetric. The mol­ecules are disordered over two sets of sites with an occupancy ratio of 0.94:0.06. In the major form, there are two intramolecular O—H...O hydrogen bonds [O...O 2.756 (4) and 2.765 (4) Å; O—H...O 144 and 146°], in which the two amidic O atoms act as acceptors. In addition, there are four intermolecular O—H...O hydrogen bonds [O...O 2.650 (3)–2.666 (3) Å; O—H...O 158–171°]; these link each mol­ecule to six others in a continuous sheet structure which contains five distinct ring motifs, two of the S(7) type, two of the R(10) type and one of the R(22) type.