2-(Phosphonomethyl)acrylic Acid Hemihydrate and Ammonium 2-(Phosphonomethyl)acrylate: Analogues of Phosphoenolpyruvate (PEP)

The structures of hydrated 2-(phosphonomethyl)acrylic acid, C₄H₇O₅P.0.5H₂O, (I) and its ammonium salt, [NH₄]⁺.(C₄H₆O₅P)^-, (II), are described. In (I), the two crystallographically independent 2-(phosphonomethyl)acrylic acid residues differ slightly in the orientation of the phosphonic group relative to the rest of the molecule. In both compounds, the phosphonic groups projects out the plane of the 2-methyleneacrylate system. The carboxylic hydroxyl is trans planar to the terminal =CH₂ group in (II) but is syn planar in (I). In both crystals, all OH and NH groups are involved in intermolecular hydrogen bonds.

-1