While the recognition of the zwitterion characteristics of OSAZ is new, similar structures have been seen in previous work . Table compares Si-O bond lengths of these similar structures to the bond lengths in this study. OSAZ has a superficial resemblance to mono-hydrated metasilicic acid H2O•(SiO(OH)2) with key differences. In OSAZ, four oxygens are covalently bonded around a silicon atom in a distorted tetrahedron, whereas in metasilicic acid, three covalently bonded oxygen atoms are trigonal planar with silicon . Interestingly, metasilicic acid is observed in gas phase ab initio studies, whereas OSAZ-like structures are observed when water molecules are explicitly added to simulations (for example, . Ab initio studies of gas phase metasilicic acid show a H2O-Si bond that is significantly longer (~1.9A) compared to OSAZ (~1.7A) for OSAZ. These seem to suggest that relaxation of the structure to a more tetrahedral geometry from a trigonal planar one is facilitated by the hydrogen bonds provided by water molecules surrounding the molecule.