2-(PHOSPHONOMETHYL)ACRYLIC ACID HEMIHYDRATE AND AMMONIUM 2-(PHOSPHONOMETHYL)ACRYLATE - ANALOGS OF PHOSPHOENOLPYRUVATE (PEP)

The structures of hydrated 2-(phosphonomethyl)acrylic acid, C4H7O5P.0. 5H(2)O, (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 phosph onic group relative to the rest of the molecule. In both compounds, th e phosphonic group projects out the plane of the 2-methyleneacrylate s ystem. The carboxylic hydroxyl is trans planar to the terminal =CH2 gr oup in (II) but is syn planar in (I). In both crystals, all OH and NH groups are involved in intermolecular hydrogen bonds.