Crystal packing in the structures of diethanolamine derivatives

Four distinct hydrogen‐bonding topologies were observed in the structures of six diethanolamine ligands. These compounds are (1R*,2R*)‐2‐(2‐hydroxyethyl)(methyl)amino]‐1,2‐diphenylethanol, C₁₇H₂₁NO₂, (I), 1‐(2S)‐2‐(hydroxydiphenylmethyl)pyrrolidin‐1‐yl]‐2‐methylpropan‐2‐ol, C₂₁H₂₇NO₂, (II), 2‐(2‐hydroxyethyl)(methyl)amino]‐1,1‐diphenylethanol, C₁₇H₂₁NO₂, (III), 1‐{(2‐hydroxy‐2‐methylpropyl)(1S)‐1‐phenylethyl]amino}‐2‐methylpropan‐2‐ol, C₁₆H₂₇NO₂, (IV), 1‐{(2R)‐2‐hydroxy‐2‐phenylethyl](1S)‐1‐phenylethyl]amino}‐2‐methylpropan‐2‐ol, C₂₀H₂₇NO₂, (V), and (1R*,2S*)‐2‐(2‐hydroxyethyl)(methyl)amino]‐1,2‐diphenylethanol, C₁₇H₂₁NO₂, (VI). In each compound, all `active' hydroxy H atoms are engaged in hydrogen bonding, but the N atoms are not involved in intermolecular hydrogen bonding. In the structures of (I), (II) and (IV)–(VI), molecules are linked into chains by intermolecular O—H...O interactions. These chains are organized in such a way as to hide the hydrophilic groups inside, and so the outer surfaces of the chains are hydrophobic. The structure of (VI) contains two distinct non‐equivalent systems of intermolecular O—H...O hydrogen bonds formed by disordered hydroxy H atoms.