JOURNAL of the Tunisian Chemical Society

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Structural and physicochemical characterization of an organic dihydrogenodiphosphate: [(CH3)2 C(NH3) CH2OH]2 H2P2O7

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Chemical preparation, crystal structure, thermal behaviour and IR absorption spectrum are given for a new organic diphosphate: [(CH3)2C(NH3)CH2OH]2H2P2O7. The 2-ammonium 2-methyl propanol dihydrogenodiphosphate is monoclinic with unit cell dimensions: a=11.441(7), b=10.360(1), c=6.799(1) Å, β=98,42(1)°, V=797.2(6) Å3, ρcal.=1.351 ρmes.=1.34, µ(AgKα)= 1,635 mm-1 space group Pc and Z=2. As in all atomic arrangements including acidic diphosphate groups one observes the formation of an infinite network of anions connected by strong H-bonds [O–O=2.464 and 2.519 Å]; infinite (H2P2O7)n layers perpendicular to the a direction, for the present structure. The differential scanning calorimetric study reveals an irreversible weak phase transition. The anhydrous title compound melts and does not crystallise when cooled at room temperature but becomes a super cooled liquid. Apparently, the compound is polymerised and an amorphous phase, as confirmed by RX powder diffraction tests, is formed.

A. Gharbi, A. Jouini

Pages 813-826

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