Monoacidic phosphonate

In the extraction studies, to be reported elsewhere, involving the use of monoacidic phosphonate extractants of the (GO)(C1CH2)P0(0H) type (where G represents phenyl groups with various substituents) with essentially constant acidities but with varying amounts of steric hindrance within the extractant molecule, the range of Kg values was 2.6 x 107 for Th(IV) and 22 for U(VI). Thus, steric hindrance within the extractant molecule was established as a very important factor in LLE sepa-rat ions. 

Fig. 3. Synthesis of diacidic and monoacidic N-1 a2etidinone phosphonates and phosphinates where TMSBr is trimethylsilyl bromide BSA is...

In addition to the conversion into phosphonochloridates as described in Section 10.10.2.1.2, phosphonate monoacids can also be activated for coupling via some of the popular reagents from standard peptide chemistry, such as BroP, 77 BOP/ and PyBOP. 79 One-pot activation and coupling of hydrogen phosphinates with a-hydroxy acids is also possible via the method outlined in Section 10.10.2.1.3. 76 The procedure outlined in Scheme 19 illustrates an optimized procedure for coupling a hindered phosphonate 57 and an a-hydroxy acid derivative via the phosphonochloridate 72 ... 

Weaver, B.S., Kappelmann, F.A. 1964. Talspeak A new method of separating americium and curium from lanthanides by extraction from an aqueous solution of aminopo-lyacetic acid complex with a monoacidic phosphate or phosphonate. ORNL-3559. 

Diacidic phosphonates (Vla-VId), i.e., those with two protons available for substitution, had a tendency to yield significant a-mounts of bis-substituted phosphonates [(RiC0CH20)2P0(R2) ] upon reaction with IV. However, it was found that careful addition (Table I) of the a-diazoketone to the phosphonate at reaction temperature minimized the formation of this by-product moreover, the bis-substituted phosphonates could be converted to the corresponding monoacids by refluxing the former with sodium iodide in methyl ethyl ketone. In this manner higher yields of phosphonates (e.g., Vllla-VIIId) could be obtained. 

In recent years, phosphorus-based polymers have been widely studied as they exhibit very unusual and interesting properties/ Whereas the ester forms are the most available compounds, monoacids and diacids can be easily obtained under mild conditions with the use of bromotrimethylsilane, opening the way to a wide range of polymers showing different properties. The latter can be explained in part by the ionization potential of phosphonic acids, which is intermediate between that of sulfonic and carbojgrlic acids due to their intermediate p/fa-... 

Excluding consideration of a multitude of representatives of solvent extraction classes (water-insoluble alcohols, ethers, acids, esters, ketones and diketones) that have been examined and found to be inadequate in some respect or another, it is the intent here to focus upon only a few representatives of just three classes of extractants (1) neutral phosphorous agents (2) monoacidic orthophosphate and phosphonate esters and (3) primary, secondary, tertiary and quaternary ammonium ion species. 

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