Dihydrogen phosphates, hydrogen bonding

Guidelines for the framework indicate that the phosphorus atom is in the middle, bonded to the four oxygen atoms. By recognizing the link between dihydrogen phosphate and phosphoric acid, we know that the hydrogen atoms bond to two of the oxygen atoms. 

A less well-documented effect is that of the phase-transition temperature of certain crystals which are very sensitive to deuteration. Some crystals of ferroelectric and antiferroelectric materials, and in particular dihydrogen phosphates and hydrogen selenites, which are extensively hydrogen bonded, display this effect (Blinc and Zeks, 1974). For some crystals, such as caesium... 

Hydrogen positions have been found in the tetragonal phase of ammonium dihydrogen phosphate, by neutron diffraction [6). The interesting feature of the O—H 0 bonds here is that the hydrogens do not lie on a line connecting the two O s. H-bond participation in the mechanism of the antiferroelectric transition at 148°K [7] is discussed. 

The quite different isotope effects in the dihydrogen salts of the phosphates and arsenates, shown in Fig. i, suggest that there hydrogen bonds are different in some way. It has been shown that the potential energy curve for the Ox—H 0IX bond in KH2P04 possesses two... 

Potassium dihydrogen phosphate is a particularly good example, since reliable data concerning the distances of the atoms in the hydrogen bonds ace available [11]. From Bacon and Pease s data, the distance between the minima of potential energy of the proton motion (if a double minimum potential curve is assumed) is between 0 3 and 0-5 A. 

Kondo, S., Hiraoka, Y., Kurumatani, N., Yano, Y., Selective recognition of dihydrogen phosphate by receptors bearing pyri-dyl moieties as hydrogen bond acceptors. Chem. Commun. 2005, 1720-1722. 

Discrete PO ions exist in normal orthophosphates. In dihydrogen phosphates such as KH2PO4 and (N2Hs)H2P04 P02(0H)2 units are hydrogen-bonded to form extended anions—see p. 318. Several X-ray and n.d. studies give P—0 close to... 

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