a-Zirconium phosphate was demonstrated t o undergo ester-interchange reactions with alkyl phosphate groups. Partial interchange was found t o occur in neat alkyl phosphate solutions. However, complete exchange is possible if the interlayer spacing of x-zirconium phosphate is first enlarged by intercalating an amine. The phosphate groups in a-zirconium phosphate are also labile and the supposed lack of reactivity previously reported is due t o the inaccessibility of the organic phosphate groups t o the interlayer spaces. Ethyl and butyl phosphates were prepared by both esterinterchange and direct precipitation methods. The reagents used contained considerable amounts of dialkyl phosphates and these are incorporated into the products along with monoalkyl phosphate. The P-phosphoglyceric acid (2hydroxy-3-phosphono-c cypropionic acid) derivative could only be prepared by direct precipitation. This compound exhibits nteresting chelation behaviour.
Zirconiumbis(hydrogenorthophosphate) hydrate, Zr-(HP0,)2-H,0, is a crystalline, insoluble ion exchanger with a layered structure.',2 It has an interlayer spacing of 7.6 A. A second form of zirconium phosphate, with an interlayer spacing of 12.2 A, is also known.3 This compound has the composition Zr(HP0,),-2H20, and while its structure is unknown, the layers are structurally different to those of the monohydrate., This compound will be referred to as y-ZrP whereas the monohydrate is termed a-ZrP.Yamanaka and co-workers 5 7 6 have reported that the hydrogenphosphate groups in y-ZrP are exchangeable with various phosphate ester ions of the type ROP03'-where R is an organic group such as phenyl, n-alkyl, etc. [equation ( l)]. Zr(HP04),-2H20 + .XROPO,~-Zr( ROP0,),(HP04)2-x-mH20 + x H P O , ~ -(1) a-ZrP does not behave in a similar fashion. However, Barret et al.' have shown that facile exchange of the layer phosphate groups of R-ZrP with HPO,'-takes place in dilute solutions.Thus, theoretically a-ZrP should exhibit ester interchange type reactions, but may be prevented from doing so by virtue of the narrow interlayer spacing which prevents diffusion of the organic phosphate ion to the exchange site.We have previously demonstrated * that ethylene oxide will react with the P-OH groups of a-ZrP as well as with those of y-ZrP.' The supposed lack of reactivity in a-ZrP is in reality lack of access to the exchange sites as its narrow interlayer spacing prevents all but the smallest molecules from diffusing into the crystal interior. The present study was designed to determine conditions under which organic phosphates and phosphonates could be made to undergo ester interchange with a-ZrP. The products obtained were then compared with those prepared by the direct precipitation method. l o
