EFFECT OF MAGNESIUM COMPLEXATION ON THE31P MIDDLE-GROUP CHEMICAL SHIFTS OF CHAIN AND RING PHOSPHATES
- 1 April 1978
- journal article
- research article
- Published by Taylor & Francis in Phosphorus and Sulfur and the Related Elements
- Vol. 4 (2), 235-238
- https://doi.org/10.1080/03086647808076571
Abstract
For pure sodium polyphosphates, Na n + 2P n O3n + 1, exhibiting 3 through 6 phosphorus atoms per molecule, the 31P chemical shift of the middle group phosphorus atoms as measured in aqueous solution (0.1 M in P) at pH 7 was seen to increase with increasing magnesium ion concentration until there was one Mg atom per polyphosphate molecule, after which the chemical shift decreased. Finally the rate of decrease diminishes and precipitation occurs. For the longer-chain phosphates, Na n + 2P n O3n + 1 with n = 8, 9, 10, or an average of 100, as well as for the ring phosphates, Na n P n O3n for n ranging from 3 through 10, an increase in magnesium concentration simply leads to a decrease in chemical shift which diminishes at the higher concentrations. These data lend additional support to the concept that polymerized phosphate anions in solution exist in preferred conformations which depend on the nature of the counteraction.Keywords
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