CARBODIIMIDE-INTERMEDIATED ESTERIFICATION OF INORGANIC PHOSPHATES AND EFFECT OF TERTIARY AMINE BASE

Detailed analysis of appropriate 31P NMR spectra shows that under the usual laboratory conditions, carbodiimide-induced condensation of Pi in a number of solvents leads to condensation only slightly beyond the metaphosphate composition in the presence of strong tertiary amines; in the absence of amine, the condensation proceeds into the ultraphosphate region about halfway between the metaphosphate and phosphoric anhydride compositions. With amine, the principal product consists of the cyclic trimetaphosphate anion, with one of the nonbridging oxygen atoms substituted by the urea resulting from hydration of the carboiimide. The well-known carbodiimide-mediated phosphorylation of alcohols with Pi is directly attributable to the high reactivity of the phosphate branch groups of the carbodiimide-generated ultraphosphates.