STRUCTURE OF PHOSPHOGLYCOLATE (PG) IN DIFFERENT IONIZATION STATES - STRUCTURE OF PHOSPHOGLYCOLIC ACID (H3PG) AND ITS SALTS - KH2PG, NAH2PG,K3H3(PG)2, NA2HPG.0.5H2O, NA5H(PG)2.4H2O AND NA3PG.4H2O

Crystalline phosphoglycolic acid and its sodium and potassium salts in different ionization states have been prepared and analyzed by X-ray diffraction. Phosphoglycolic acid, C2H5O6P (f), M(r) = 156.03, monocli nic, P2(1)/c, a = 14.860 (5), b = 4.850 (2), c = 8.221 (4) angstrom, b eta = 105.58 (4)degrees, V = 570.7 (5) angstrom3, Z = 4, D(x) = 1.816 (2) g cm-3, lambda(Mo Kalpha) = 0.71069 angstrom, mu = 4.3 cm-1, F(000 ) = 320, T = 295(2)K, final R = 0.0254 for 1152 observed reflections. Potassium phosphoglycolate, K+ .C2H4O6P- (II), M(r) = 194.12, monoclin ic, P2(1), a = 10.570 (6), b = 4.588 (3), c = 7.935 (4) angstrom, beta = 126.92 (4)degrees, V = 307.6 (4) angstrom3, Z = 2, D(m) = 2.07, D(x ) = 2.095 (3) g cm-3, mu(Mo Kalpha) = 10.8 cm-1, F(000) = 196, T = 300 (2) K, final R = 0.026 for 1818 observed (hkl and hklBAR) reflections . Sodium phosphoglycolate, Na+.C2H4O6P (III), M(r) = 178.01, monoclini c, P2/n, a = 9.782 (6), b = 5.366 (3), c = 11.175 (9) angstrom, beta = 91.39 (6)degrees, V = 586.4 (7) angstrom3, Z = 4, D(m) = 1.98, D(x) = 2.016 (3) g cm-3, mu(Mo Kalpha) = 4.9 cm-1, F(000) = 360, T = 301 (2) K, final R = 0.031 for 1051 observed reflections. Tripotassium bis(ph osphoglycolate), 3K+.(C2H3O6P...H...C2H3O6P)3- (IV), M(r) = 426.34, tr iclinic, P1BAR, a = 8.643 (6), b = 9.013 (7), c = 9.907 (7) angstrom, alpha = 113.97 (6), beta = 95.41 (6), gamma = 95.01 (6)degrees, V = 69 5.3 (9) angstrom3, Z = 2, D(m) = 2.03, D(x) = 2.036 (4) g cm-3, mu(Mo Kalpha) = 12.6 cm-1, F(000) = 428, T = 296 (2) K, final R = 0.034 for 2112 observed reflections. Disodium phosphoglycolate hemihydrate, 2Na.(C2H3O6P)2-.0.5H2O (V), M(r) = 209.00, orthorhombic, P2(1)2(1)2, a = 10. 520 (6), b = 13.442 (6), c = 8.996 (5) angstrom, V = 1272.1 (12) a ngstrom3, Z = 8, D(m) = 2.13, D(x) = 2.182 (3) g cm-3, mu(Mo Kalpha) = 5.4 cm-1, F(000) = 840, T = 299 (3) K, final R = 0.0303 for 2409 obse rved (hkl and hklBAR) reflections. Pentasodium bis(phosphoglycolate) t etrahydrate, 5Na+.-(C2H2O6P...H...C2H2O6P)5-.4H2O M(r) = 494.04, monoc linic, C2/c, a = 6.960 (4), b = 17.793 (12), c = 13.151 (9) angstrom, beta = 96.88 (5)degrees, V = 1617 (2) angstrom3, Z = 4, D(m) = 1.98, D (x) = 2.029(3) g cm-3, mu(Mo Kalpha) = 4.7 cm-1, F(000)= 1000, T = 301 (2) K, final R = 0.0281 for 1189 observed reflections. Trisodium phos phoglycolate tetrahydrate, 3Na+.(C2H2O6P)3-.4H2O (VII), M(r) = 294.04, orthorhombic, Pbcn, a = 10.617 (9), b = 6.977 (8), c = 27.65 (2) angs trom, V = 2048 (4) angstrom3, Z = 8, D(x) = 1.907 (4) g cm-3, lambda(C u Kalpha) = 1.5418 angstrom, mu = 41.2 cm-1, F(000) = 1200, T = 295 (2 ) K, final R = 0.030 for 1567 non-zero reflections. Trisodium phosphog lycolate tetrahydrate, 3Na+.-(C2H2O6P)3-.4H2O (VIII), M(r) = 294.04, m onoclinic, P2(1)/n, a = 6.243 (6), b = 26.08 (2), c = 6.763 (7) angstr om, beta = 115.29 (9)degrees, V = 995.6 (18) angstrom3, Z = 4, D(m) = 1.98, D(x) = 1.962 (4) g cm-3, mu(Cu Kalpha) = 42.4 cm-1, F(000) = 600 , T = 296 (2) K, final R = 0.0264 for 1467 non-zero reflections. The o rientation of the phosphate group relative to the glycolate moiety is different in each compound and suggests conformational flexibility aro und the C-O(ester) bond in water solutions. There is a tendency for th e ester O atom to lie in the plane of the acetate group. The P-O(ester ) bond length changes slowly and irregularly with the protonation leve l, from 1.566 (2) angstrom in H3PG (I) to 1.635 (2) angstrom in the tr ianion (VIII).